hi folks, we are defining a device migration compatibility interface that helps upper layer stack like openstack/ovirt/libvirt to check if two devices are live migration compatible. The "devices" here could be MDEVs, physical devices, or hybrid of the two. e.g. we could use it to check whether - a src MDEV can migrate to a target MDEV, - a src VF in SRIOV can migrate to a target VF in SRIOV, - a src MDEV can migration to a target VF in SRIOV. (e.g. SIOV/SRIOV backward compatibility case) The upper layer stack could use this interface as the last step to check if one device is able to migrate to another device before triggering a real live migration procedure. we are not sure if this interface is of value or help to you. please don't hesitate to drop your valuable comments. (1) interface definition The interface is defined in below way: __ userspace /\ \ / \write / read \ ________/__________ ___\|/_____________ | migration_version | | migration_version |-->check migration --------------------- --------------------- compatibility device A device B a device attribute named migration_version is defined under each device's sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). userspace tools read the migration_version as a string from the source device, and write it to the migration_version sysfs attribute in the target device. The userspace should treat ANY of below conditions as two devices not compatible: - any one of the two devices does not have a migration_version attribute - error when reading from migration_version attribute of one device - error when writing migration_version string of one device to migration_version attribute of the other device The string read from migration_version attribute is defined by device vendor driver and is completely opaque to the userspace. for a Intel vGPU, string format can be defined like "parent device PCI ID" + "version of gvt driver" + "mdev type" + "aggregator count". for an NVMe VF connecting to a remote storage. it could be "PCI ID" + "driver version" + "configured remote storage URL" for a QAT VF, it may be "PCI ID" + "driver version" + "supported encryption set". (to avoid namespace confliction from each vendor, we may prefix a driver name to each migration_version string. e.g. i915-v1-8086-591d-i915-GVTg_V5_8-1) (2) backgrounds The reason we hope the migration_version string is opaque to the userspace is that it is hard to generalize standard comparing fields and comparing methods for different devices from different vendors. Though userspace now could still do a simple string compare to check if two devices are compatible, and result should also be right, it's still too limited as it excludes the possible candidate whose migration_version string fails to be equal. e.g. an MDEV with mdev_type_1, aggregator count 3 is probably compatible with another MDEV with mdev_type_3, aggregator count 1, even their migration_version strings are not equal. (assumed mdev_type_3 is of 3 times equal resources of mdev_type_1). besides that, driver version + configured resources are all elements demanding to take into account. So, we hope leaving the freedom to vendor driver and let it make the final decision in a simple reading from source side and writing for test in the target side way. we then think the device compatibility issues for live migration with assigned devices can be divided into two steps: a. management tools filter out possible migration target devices. Tags could be created according to info from product specification. we think openstack/ovirt may have vendor proprietary components to create those customized tags for each product from each vendor.

for Intel vGPU, with a vGPU(a MDEV device) in source side, the tags to search target vGPU are like: a tag for compatible parent PCI IDs, a tag for a range of gvt driver versions, a tag for a range of mdev type + aggregator count for NVMe VF, the tags to search target VF may be like: a tag for compatible PCI IDs, a tag for a range of driver versions, a tag for URL of configured remote storage.

b. with the output from step a, openstack/ovirt/libvirt could use our proposed device migration compatibility interface to make sure the two devices are indeed live migration compatible before launching the real live migration process to start stream copying, src device stopping and target device resuming. It is supposed that this step would not bring any performance penalty as -in kernel it's just a simple string decoding and comparing -in openstack/ovirt, it could be done by extending current function check_can_live_migrate_destination, along side claiming target resources.[1]

[1] https://specs.openstack.org/openstack/nova-specs/specs/stein/approved/lib... Thanks Yan

On Tue, Jul 14, 2020 at 07:29:57AM +0800, Yan Zhao wrote: > hi folks, > we are defining a device migration compatibility interface that helps upper > layer stack like openstack/ovirt/libvirt to check if two devices are > live migration compatible. > The "devices" here could be MDEVs, physical devices, or hybrid of the two. > e.g. we could use it to check whether > - a src MDEV can migrate to a target MDEV, > - a src VF in SRIOV can migrate to a target VF in SRIOV, > - a src MDEV can migration to a target VF in SRIOV. > (e.g. SIOV/SRIOV backward compatibility case) > > The upper layer stack could use this interface as the last step to check > if one device is able to migrate to another device before triggering a real > live migration procedure. > we are not sure if this interface is of value or help to you. please don't > hesitate to drop your valuable comments. > > > (1) interface definition > The interface is defined in below way: > > __ userspace > /\ \ > / \write > / read \ > ________/__________ ___\|/_____________ > | migration_version | | migration_version |-->check migration > --------------------- --------------------- compatibility > device A device B > > > a device attribute named migration_version is defined under each device's > sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). > userspace tools read the migration_version as a string from the source device, > and write it to the migration_version sysfs attribute in the target device. > > The userspace should treat ANY of below conditions as two devices not compatible: > - any one of the two devices does not have a migration_version attribute > - error when reading from migration_version attribute of one device > - error when writing migration_version string of one device to > migration_version attribute of the other device > > The string read from migration_version attribute is defined by device vendor > driver and is completely opaque to the userspace. > for a Intel vGPU, string format can be defined like > "parent device PCI ID" + "version of gvt driver" + "mdev type" + "aggregator count". > > for an NVMe VF connecting to a remote storage. it could be > "PCI ID" + "driver version" + "configured remote storage URL" > > for a QAT VF, it may be > "PCI ID" + "driver version" + "supported encryption set". > > (to avoid namespace confliction from each vendor, we may prefix a driver name to > each migration_version string. e.g. i915-v1-8086-591d-i915-GVTg_V5_8-1)

> (2) backgrounds > > The reason we hope the migration_version string is opaque to the userspace > is that it is hard to generalize standard comparing fields and comparing > methods for different devices from different vendors. > Though userspace now could still do a simple string compare to check if > two devices are compatible, and result should also be right, it's still > too limited as it excludes the possible candidate whose migration_version > string fails to be equal. > e.g. an MDEV with mdev_type_1, aggregator count 3 is probably compatible > with another MDEV with mdev_type_3, aggregator count 1, even their > migration_version strings are not equal. > (assumed mdev_type_3 is of 3 times equal resources of mdev_type_1). > > besides that, driver version + configured resources are all elements demanding > to take into account. > > So, we hope leaving the freedom to vendor driver and let it make the final decision > in a simple reading from source side and writing for test in the target side way. > > > we then think the device compatibility issues for live migration with assigned > devices can be divided into two steps: > a. management tools filter out possible migration target devices. > Tags could be created according to info from product specification. > we think openstack/ovirt may have vendor proprietary components to create > those customized tags for each product from each vendor. > for Intel vGPU, with a vGPU(a MDEV device) in source side, the tags to > search target vGPU are like: > a tag for compatible parent PCI IDs, > a tag for a range of gvt driver versions, > a tag for a range of mdev type + aggregator count > > for NVMe VF, the tags to search target VF may be like: > a tag for compatible PCI IDs, > a tag for a range of driver versions, > a tag for URL of configured remote storage.

Requiring management application developers to figure out this possible compatibility based on prod specs is really unrealistic. Product specs are typically as clear as mud, and with the suggestion we consider different rules for different types of devices, add up to a huge amount of complexity. This isn't something app developers should have to spend their time figuring out.

The suggestion that we make use of vendor proprietary helper components is totally unacceptable. We need to be able to build a solution that works with exclusively an open source software stack.

IMHO there needs to be a mechanism for the kernel to report via sysfs what versions are supported on a given device. This puts the job of reporting compatible versions directly under the responsibility of the vendor who writes the kernel driver for it. They are the ones with the best knowledge of the hardware they've built and the rules around its compatibility.

On Tue, 2020-07-14 at 11:21 +0100, Daniel P. Berrangé wrote: > On Tue, Jul 14, 2020 at 07:29:57AM +0800, Yan Zhao wrote: > > hi folks, > > we are defining a device migration compatibility interface that helps upper > > layer stack like openstack/ovirt/libvirt to check if two devices are > > live migration compatible. > > The "devices" here could be MDEVs, physical devices, or hybrid of the two. > > e.g. we could use it to check whether > > - a src MDEV can migrate to a target MDEV, mdev live migration is completely possible to do but i agree with Dan barrange's comments from the point of view of openstack integration i dont see calling out to a vender sepecific tool to be an accpetable

solutions for device compatiablity checking. the sys filesystem that describs the mdevs that can be created shoudl also contain the relevent infomation such taht nova could integrate it via libvirt xml representation or directly retrive the info from sysfs. > > - a src VF in SRIOV can migrate to a target VF in SRIOV, so vf to vf migration is not possible in the general case as there is no standarised way to transfer teh device state as part of the siorv specs produced by the pci-sig as such there is not vender neutral way to support sriov live migration.

> > - a src MDEV can migration to a target VF in SRIOV. that also makes this unviable > > (e.g. SIOV/SRIOV backward compatibility case) > > > > The upper layer stack could use this interface as the last step to check > > if one device is able to migrate to another device before triggering a real > > live migration procedure. well actully that is already too late really. ideally we would want to do this compaiablity check much sooneer to avoid the migration failing. in an openstack envionment at least by the time we invoke libvirt (assuming your using the libvirt driver) to do the migration we have alreaedy finished schduling the instance to the new host. if if we do the compatiablity check at this point and it fails then the live migration is aborted and will not be retired. These types of late check lead to a poor user experince as unless you check the migration detial it basically looks like the migration was ignored as it start to migrate and then continuge running on the orgininal host. when using generic pci passhotuhg with openstack, the pci alias is intended to reference a single vendor id/product id so you will have 1+ alias for each type of device. that allows openstack to schedule based on the availability of a compatibale device because we track inventories of pci devices and can query that when selecting a host. if we were to support mdev live migration in the future we would want to take the same declarative approch. 1 interospec the capability of the deivce we manage 2 create inventories of the allocatable devices and there capabilities 3 schdule the instance to a host based on the device-type/capabilities and claim it atomicly to prevent raceces 4 have the lower level hyperviors do addtional validation if need prelive migration. this proposal seams to be targeting extending step 4 where as ideally we should focuse on providing the info that would be relevant in set 1 preferably in a vendor neutral way vai a kernel interface like /sys.

> > we are not sure if this interface is of value or help to you. please don't > > hesitate to drop your valuable comments. > > > > > > (1) interface definition > > The interface is defined in below way: > > > > __ userspace > > /\ \ > > / \write > > / read \ > > ________/__________ ___\|/_____________ > > | migration_version | | migration_version |-->check migration > > --------------------- --------------------- compatibility > > device A device B > > > > > > a device attribute named migration_version is defined under each device's > > sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). this might be useful as we could tag the inventory with the migration version and only might to devices with the same version

> > userspace tools read the migration_version as a string from the source device, > > and write it to the migration_version sysfs attribute in the target device. this would not be useful as the schduler cannot directlly connect to the compute host and even if it could it would be extreamly slow to do this for 1000s of hosts and potentally multiple devices per host.

> > > > The userspace should treat ANY of below conditions as two devices not compatible: > > - any one of the two devices does not have a migration_version attribute > > - error when reading from migration_version attribute of one device > > - error when writing migration_version string of one device to > > migration_version attribute of the other device > > > > The string read from migration_version attribute is defined by device vendor > > driver and is completely opaque to the userspace. opaque vendor specific stings that higher level orchestros have to pass form host to host and cant reason about are evil, when allowed they prolifroate and makes any idea of a vendor nutral abstraction and interoperablity between systems impossible to reason about. that said there is a way to make it opaue but still useful to userspace. see below > > for a Intel vGPU, string format can be defined like > > "parent device PCI ID" + "version of gvt driver" + "mdev type" + "aggregator count". > > > > for an NVMe VF connecting to a remote storage. it could be > > "PCI ID" + "driver version" + "configured remote storage URL" > > > > for a QAT VF, it may be > > "PCI ID" + "driver version" + "supported encryption set". > > > > (to avoid namespace confliction from each vendor, we may prefix a driver name to > > each migration_version string. e.g. i915-v1-8086-591d-i915-GVTg_V5_8-1) honestly i would much prefer if the version string was just a semver string. e.g. {major}.{minor}.{bugfix} if you do a driver/frimware update and break compatiablity with an older version bump the major version. if you add optional a feature that does not break backwards compatiablity if you migrate an older instance to the new host then just bump the minor/feature number. if you have a fix for a bug that does not change the feature set or compatiblity backwards or forwards then bump the bugfix number then the check is as simple as 1.) is the mdev type the same 2.) is the major verion the same 3.) am i going form the same version to same version or same version to newer version if all 3 are true we can migrate. e.g. 2.0.1 -> 2.1.1 (ok same major version and migrating from older feature release to newer feature release) 2.1.1 -> 2.0.1 (not ok same major version and migrating from new feature release to old feature release may be incompatable) 2.0.0 -> 3.0.0 (not ok chaning major version) 2.0.1 -> 2.0.0 (ok same major and minor version, all bugfixs in the same minor release should be compatibly)

we dont need vendor to rencode the driver name or vendor id and product id in the string. that info is alreay available both to the device driver and to userspace via /sys already we just need to know if version of the same mdev are compatiable so a simple semver version string which is well know in the software world at least is a clean abstration we can reuse.

On Tue, Jul 14, 2020 at 10:16:16AM -0600, Alex Williamson wrote: > On Tue, 14 Jul 2020 11:21:29 +0100 > Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > > > On Tue, Jul 14, 2020 at 07:29:57AM +0800, Yan Zhao wrote: > > > > > > The string read from migration_version attribute is defined by device vendor > > > driver and is completely opaque to the userspace. > > > for a Intel vGPU, string format can be defined like > > > "parent device PCI ID" + "version of gvt driver" + "mdev type" + "aggregator count". > > > > > > for an NVMe VF connecting to a remote storage. it could be > > > "PCI ID" + "driver version" + "configured remote storage URL" > > > > > > for a QAT VF, it may be > > > "PCI ID" + "driver version" + "supported encryption set". > > > > > > (to avoid namespace confliction from each vendor, we may prefix a driver name to > > > each migration_version string. e.g. i915-v1-8086-591d-i915-GVTg_V5_8-1) > > It's very strange to define it as opaque and then proceed to describe > the contents of that opaque string. The point is that its contents > are defined by the vendor driver to describe the device, driver version, > and possibly metadata about the configuration of the device. One > instance of a device might generate a different string from another. > The string that a device produces is not necessarily the only string > the vendor driver will accept, for example the driver might support > backwards compatible migrations. > > IMHO there needs to be a mechanism for the kernel to report via sysfs > > what versions are supported on a given device. This puts the job of > > reporting compatible versions directly under the responsibility of the > > vendor who writes the kernel driver for it. They are the ones with the > > best knowledge of the hardware they've built and the rules around its > > compatibility. > > The version string discussed previously is the version string that > represents a given device, possibly including driver information, > configuration, etc. I think what you're asking for here is an > enumeration of every possible version string that a given device could > accept as an incoming migration stream. If we consider the string as > opaque, that means the vendor driver needs to generate a separate > string for every possible version it could accept, for every possible > configuration option. That potentially becomes an excessive amount of > data to either generate or manage. > > Am I overestimating how vendors intend to use the version string? If I'm interpreting your reply & the quoted text orrectly, the version string isn't really a version string in any normal sense of the word "version". Instead it sounds like string encoding a set of features in some arbitrary vendor specific format, which they parse and do compatibility checks on individual pieces ? One or more parts may contain a version number, but its much more than just a version. If that's correct, then I'd prefer we didn't call it a version string, instead call it a "capability string" to make it clear it is expressing a much more general concept, but...

> We'd also need to consider devices that we could create, for instance > providing the same interface enumeration prior to creating an mdev > device to have a confidence level that the new device would be a valid > target. > > We defined the string as opaque to allow vendor flexibility and because > defining a common format is hard. Do we need to revisit this part of > the discussion to define the version string as non-opaque with parsing > rules, probably with separate incoming vs outgoing interfaces? Thanks, ..even if the huge amount of flexibility is technically relevant from the POV of the hardware/drivers, we should consider whether management apps actually want, or can use, that level of flexibility. The task of picking which host to place a VM on has alot of factors to consider, and when there are a large number of hosts, the total amount of information to check gets correspondingly large. The placement process is also fairly performance critical. Running complex algorithmic logic to check compatibility of devices based on a arbitrary set of rules is likely to be a performance challenge. A flat list of supported strings is a much simpler thing to check as it reduces down to a simple set membership test. IOW, even if there's some complex set of device type / vendor specific rules to check for compatibility, I fear apps will ignore them and just define a very simplified list of compatible string, and ignore all the extra flexibility.

I'm sure OpenStack maintainers can speak to this more, as they've put alot of work into their scheduling engine to optimize the way it places VMs largely driven from simple structured data reported from hosts.

On Tue, 14 Jul 2020 11:21:29 +0100 Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > On Tue, Jul 14, 2020 at 07:29:57AM +0800, Yan Zhao wrote: > > hi folks, > > we are defining a device migration compatibility interface that helps upper > > layer stack like openstack/ovirt/libvirt to check if two devices are > > live migration compatible. > > The "devices" here could be MDEVs, physical devices, or hybrid of the two. > > e.g. we could use it to check whether > > - a src MDEV can migrate to a target MDEV, > > - a src VF in SRIOV can migrate to a target VF in SRIOV, > > - a src MDEV can migration to a target VF in SRIOV. > > (e.g. SIOV/SRIOV backward compatibility case) > > > > The upper layer stack could use this interface as the last step to check > > if one device is able to migrate to another device before triggering a real > > live migration procedure. > > we are not sure if this interface is of value or help to you. please don't > > hesitate to drop your valuable comments. > > > > > > (1) interface definition > > The interface is defined in below way: > > > > __ userspace > > /\ \ > > / \write > > / read \ > > ________/__________ ___\|/_____________ > > | migration_version | | migration_version |-->check migration > > --------------------- --------------------- compatibility > > device A device B > > > > > > a device attribute named migration_version is defined under each device's > > sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). > > userspace tools read the migration_version as a string from the source device, > > and write it to the migration_version sysfs attribute in the target device. > > > > The userspace should treat ANY of below conditions as two devices not compatible: > > - any one of the two devices does not have a migration_version attribute > > - error when reading from migration_version attribute of one device > > - error when writing migration_version string of one device to > > migration_version attribute of the other device > > > > The string read from migration_version attribute is defined by device vendor > > driver and is completely opaque to the userspace. > > for a Intel vGPU, string format can be defined like > > "parent device PCI ID" + "version of gvt driver" + "mdev type" + "aggregator count".

> > > for an NVMe VF connecting to a remote storage. it could be > > "PCI ID" + "driver version" + "configured remote storage URL"

> > > > for a QAT VF, it may be > > "PCI ID" + "driver version" + "supported encryption set". > > > > (to avoid namespace confliction from each vendor, we may prefix a driver name to > > each migration_version string. e.g. i915-v1-8086-591d-i915-GVTg_V5_8-1) It's very strange to define it as opaque and then proceed to describe the contents of that opaque string. The point is that its contents are defined by the vendor driver to describe the device, driver version, and possibly metadata about the configuration of the device. One instance of a device might generate a different string from another. The string that a device produces is not necessarily the only string the vendor driver will accept, for example the driver might support backwards compatible migrations. > > (2) backgrounds > > > > The reason we hope the migration_version string is opaque to the userspace > > is that it is hard to generalize standard comparing fields and comparing > > methods for different devices from different vendors. > > Though userspace now could still do a simple string compare to check if > > two devices are compatible, and result should also be right, it's still > > too limited as it excludes the possible candidate whose migration_version > > string fails to be equal. > > e.g. an MDEV with mdev_type_1, aggregator count 3 is probably compatible > > with another MDEV with mdev_type_3, aggregator count 1, even their > > migration_version strings are not equal. > > (assumed mdev_type_3 is of 3 times equal resources of mdev_type_1). > > > > besides that, driver version + configured resources are all elements demanding > > to take into account. > > > > So, we hope leaving the freedom to vendor driver and let it make the final decision > > in a simple reading from source side and writing for test in the target side way. > > > > > > we then think the device compatibility issues for live migration with assigned > > devices can be divided into two steps: > > a. management tools filter out possible migration target devices. > > Tags could be created according to info from product specification. > > we think openstack/ovirt may have vendor proprietary components to create > > those customized tags for each product from each vendor. > > > for Intel vGPU, with a vGPU(a MDEV device) in source side, the tags to > > search target vGPU are like: > > a tag for compatible parent PCI IDs, > > a tag for a range of gvt driver versions, > > a tag for a range of mdev type + aggregator count > > > > for NVMe VF, the tags to search target VF may be like: > > a tag for compatible PCI IDs, > > a tag for a range of driver versions, > > a tag for URL of configured remote storage. I interpret this as hand waving, ie. the first step is for management tools to make a good guess :-\ We don't seem to be willing to say that a given mdev type can only migrate to a device with that same type. There's this aggregation discussion happening separately where a base mdev type might be created or later configured to be equivalent to a different type. The vfio migration API we've defined is also not limited to mdev devices, for example we could create vendor specific quirks or hooks to provide migration support for a physical PF/VF device. Within the realm of possibility then is that we could migrate between a physical device and an mdev device, which are simply different degrees of creating a virtualization layer in front of the device. > Requiring management application developers to figure out this possible > compatibility based on prod specs is really unrealistic. Product specs > are typically as clear as mud, and with the suggestion we consider > different rules for different types of devices, add up to a huge amount > of complexity. This isn't something app developers should have to spend > their time figuring out. Agreed. > The suggestion that we make use of vendor proprietary helper components > is totally unacceptable. We need to be able to build a solution that > works with exclusively an open source software stack. I'm surprised to see this as well, but I'm not sure if Yan was really suggesting proprietary software so much as just vendor specific knowledge. > IMHO there needs to be a mechanism for the kernel to report via sysfs > what versions are supported on a given device. This puts the job of > reporting compatible versions directly under the responsibility of the > vendor who writes the kernel driver for it. They are the ones with the > best knowledge of the hardware they've built and the rules around its > compatibility. The version string discussed previously is the version string that represents a given device, possibly including driver information, configuration, etc. I think what you're asking for here is an enumeration of every possible version string that a given device could accept as an incoming migration stream. If we consider the string as opaque, that means the vendor driver needs to generate a separate string for every possible version it could accept, for every possible configuration option. That potentially becomes an excessive amount of data to either generate or manage.

Am I overestimating how vendors intend to use the version string? We'd also need to consider devices that we could create, for instance providing the same interface enumeration prior to creating an mdev device to have a confidence level that the new device would be a valid target. We defined the string as opaque to allow vendor flexibility and because defining a common format is hard. Do we need to revisit this part of the discussion to define the version string as non-opaque with parsing rules, probably with separate incoming vs outgoing interfaces? Thanks, Alex

On Tue, 14 Jul 2020 18:19:46 +0100 "Dr. David Alan Gilbert" <dgilbert(a)redhat.com&gt; wrote: > * Alex Williamson (alex.williamson(a)redhat.com) wrote: > > On Tue, 14 Jul 2020 11:21:29 +0100 > > Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > > > > > On Tue, Jul 14, 2020 at 07:29:57AM +0800, Yan Zhao wrote: > > > > hi folks, > > > > we are defining a device migration compatibility interface that helps upper > > > > layer stack like openstack/ovirt/libvirt to check if two devices are > > > > live migration compatible. > > > > The "devices" here could be MDEVs, physical devices, or hybrid of the two. > > > > e.g. we could use it to check whether > > > > - a src MDEV can migrate to a target MDEV, > > > > - a src VF in SRIOV can migrate to a target VF in SRIOV, > > > > - a src MDEV can migration to a target VF in SRIOV. > > > > (e.g. SIOV/SRIOV backward compatibility case) > > > > > > > > The upper layer stack could use this interface as the last step to check > > > > if one device is able to migrate to another device before triggering a real > > > > live migration procedure. > > > > we are not sure if this interface is of value or help to you. please don't > > > > hesitate to drop your valuable comments. > > > > > > > > > > > > (1) interface definition > > > > The interface is defined in below way: > > > > > > > > __ userspace > > > > /\ \ > > > > / \write > > > > / read \ > > > > ________/__________ ___\|/_____________ > > > > | migration_version | | migration_version |-->check migration > > > > --------------------- --------------------- compatibility > > > > device A device B > > > > > > > > > > > > a device attribute named migration_version is defined under each device's > > > > sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). > > > > userspace tools read the migration_version as a string from the source device, > > > > and write it to the migration_version sysfs attribute in the target device. > > > > > > > > The userspace should treat ANY of below conditions as two devices not compatible: > > > > - any one of the two devices does not have a migration_version attribute > > > > - error when reading from migration_version attribute of one device > > > > - error when writing migration_version string of one device to > > > > migration_version attribute of the other device > > > > > > > > The string read from migration_version attribute is defined by device vendor > > > > driver and is completely opaque to the userspace. > > > > for a Intel vGPU, string format can be defined like > > > > "parent device PCI ID" + "version of gvt driver" + "mdev type" + "aggregator count". > > > > > > > > for an NVMe VF connecting to a remote storage. it could be > > > > "PCI ID" + "driver version" + "configured remote storage URL" > > > > > > > > for a QAT VF, it may be > > > > "PCI ID" + "driver version" + "supported encryption set". > > > > > > > > (to avoid namespace confliction from each vendor, we may prefix a driver name to > > > > each migration_version string. e.g. i915-v1-8086-591d-i915-GVTg_V5_8-1) > > > > It's very strange to define it as opaque and then proceed to describe > > the contents of that opaque string. The point is that its contents > > are defined by the vendor driver to describe the device, driver version, > > and possibly metadata about the configuration of the device. One > > instance of a device might generate a different string from another. > > The string that a device produces is not necessarily the only string > > the vendor driver will accept, for example the driver might support > > backwards compatible migrations. > > (As I've said in the previous discussion, off one of the patch series) > > My view is it makes sense to have a half-way house on the opaqueness of > this string; I'd expect to have an ID and version that are human > readable, maybe a device ID/name that's human interpretable and then a > bunch of other cruft that maybe device/vendor/version specific. > > I'm thinking that we want to be able to report problems and include the > string and the user to be able to easily identify the device that was > complaining and notice a difference in versions, and perhaps also use > it in compatibility patterns to find compatible hosts; but that does > get tricky when it's a 'ask the device if it's compatible'. In the reply I just sent to Dan, I gave this example of what a "compatibility string" might look like represented as json: { "device_api": "vfio-pci", "vendor": "vendor-driver-name", "version": { "major": 0, "minor": 1 }, "vfio-pci": { // Based on above device_api "vendor": 0x1234, // Values for the exposed device "device": 0x5678, // Possibly further parameters for a more specific match }, "mdev_attrs": [ { "attribute0": "VALUE" } ] } Are you thinking that we might allow the vendor to include a vendor specific array where we'd simply require that both sides have matching fields and values? ie. "vendor_fields": [ { "unknown_field0": "unknown_value0" }, { "unknown_field1": "unknown_value1" }, ] We could certainly make that part of the spec, but I can't really figure the value of it other than to severely restrict compatibility, which the vendor could already do via the version.major value. Maybe they'd want to put a build timestamp, random uuid, or source sha1 into such a field to make absolutely certain compatibility is only determined between identical builds? Thanks,

On Tue, 14 Jul 2020 18:19:46 +0100 "Dr. David Alan Gilbert" <dgilbert(a)redhat.com&gt; wrote: > * Alex Williamson (alex.williamson(a)redhat.com) wrote: > > On Tue, 14 Jul 2020 11:21:29 +0100 Daniel P. Berrangé > > <berrange(a)redhat.com&gt; wrote: > > > > > On Tue, Jul 14, 2020 at 07:29:57AM +0800, Yan Zhao wrote: > > > > hi folks, > > > > we are defining a device migration compatibility interface > > > > that helps upper layer stack like openstack/ovirt/libvirt to > > > > check if two devices are live migration compatible. > > > > The "devices" here could be MDEVs, physical devices, or hybrid of the two. > > > > e.g. we could use it to check whether > > > > - a src MDEV can migrate to a target MDEV, > > > > - a src VF in SRIOV can migrate to a target VF in SRIOV, > > > > - a src MDEV can migration to a target VF in SRIOV. > > > > (e.g. SIOV/SRIOV backward compatibility case) > > > > > > > > The upper layer stack could use this interface as the last > > > > step to check if one device is able to migrate to another > > > > device before triggering a real live migration procedure. > > > > we are not sure if this interface is of value or help to you. > > > > please don't hesitate to drop your valuable comments. > > > > > > > > > > > > (1) interface definition > > > > The interface is defined in below way: > > > > > > > > __ userspace > > > > /\ \ > > > > / \write > > > > / read \ > > > > ________/__________ ___\|/_____________ > > > > | migration_version | | migration_version |-->check migration > > > > --------------------- --------------------- compatibility > > > > device A device B > > > > > > > > > > > > a device attribute named migration_version is defined under > > > > each device's sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). > > > > userspace tools read the migration_version as a string from > > > > the source device, and write it to the migration_version sysfs attribute in the target device. > > > > > > > > The userspace should treat ANY of below conditions as two devices not compatible: > > > > - any one of the two devices does not have a migration_version > > > > attribute > > > > - error when reading from migration_version attribute of one > > > > device > > > > - error when writing migration_version string of one device to > > > > migration_version attribute of the other device > > > > > > > > The string read from migration_version attribute is defined by > > > > device vendor driver and is completely opaque to the userspace. > > > > for a Intel vGPU, string format can be defined like "parent > > > > device PCI ID" + "version of gvt driver" + "mdev type" + "aggregator count". > > > > > > > > for an NVMe VF connecting to a remote storage. it could be > > > > "PCI ID" + "driver version" + "configured remote storage URL" > > > > > > > > for a QAT VF, it may be > > > > "PCI ID" + "driver version" + "supported encryption set". > > > > > > > > (to avoid namespace confliction from each vendor, we may > > > > prefix a driver name to each migration_version string. e.g. > > > > i915-v1-8086-591d-i915-GVTg_V5_8-1) > > > > It's very strange to define it as opaque and then proceed to > > describe the contents of that opaque string. The point is that > > its contents are defined by the vendor driver to describe the > > device, driver version, and possibly metadata about the > > configuration of the device. One instance of a device might generate a different string from another. > > The string that a device produces is not necessarily the only > > string the vendor driver will accept, for example the driver might > > support backwards compatible migrations. > > (As I've said in the previous discussion, off one of the patch > series) > > My view is it makes sense to have a half-way house on the opaqueness > of this string; I'd expect to have an ID and version that are human > readable, maybe a device ID/name that's human interpretable and then > a bunch of other cruft that maybe device/vendor/version specific. > > I'm thinking that we want to be able to report problems and include > the string and the user to be able to easily identify the device > that was complaining and notice a difference in versions, and > perhaps also use it in compatibility patterns to find compatible > hosts; but that does get tricky when it's a 'ask the device if it's compatible'. In the reply I just sent to Dan, I gave this example of what a "compatibility string" might look like represented as json: { "device_api": "vfio-pci", "vendor": "vendor-driver-name", "version": { "major": 0, "minor": 1 }, "vfio-pci": { // Based on above device_api "vendor": 0x1234, // Values for the exposed device "device": 0x5678, // Possibly further parameters for a more specific match }, "mdev_attrs": [ { "attribute0": "VALUE" } ] } Are you thinking that we might allow the vendor to include a vendor specific array where we'd simply require that both sides have matching fields and values? ie. "vendor_fields": [ { "unknown_field0": "unknown_value0" }, { "unknown_field1": "unknown_value1" }, ] We could certainly make that part of the spec, but I can't really figure the value of it other than to severely restrict compatibility, which the vendor could already do via the version.major value. Maybe they'd want to put a build timestamp, random uuid, or source sha1 into such a field to make absolutely certain compatibility is only determined between identical builds? Thanks,

On Tue, Jul 14, 2020 at 02:59:48PM -0600, Alex Williamson wrote: > On Tue, 14 Jul 2020 18:19:46 +0100 > "Dr. David Alan Gilbert" <dgilbert(a)redhat.com&gt; wrote: > > > * Alex Williamson (alex.williamson(a)redhat.com) wrote: > > > On Tue, 14 Jul 2020 11:21:29 +0100 > > > Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > > > > > > > On Tue, Jul 14, 2020 at 07:29:57AM +0800, Yan Zhao wrote: > > > > > hi folks, > > > > > we are defining a device migration compatibility interface that helps upper > > > > > layer stack like openstack/ovirt/libvirt to check if two devices are > > > > > live migration compatible. > > > > > The "devices" here could be MDEVs, physical devices, or hybrid of the two. > > > > > e.g. we could use it to check whether > > > > > - a src MDEV can migrate to a target MDEV, > > > > > - a src VF in SRIOV can migrate to a target VF in SRIOV, > > > > > - a src MDEV can migration to a target VF in SRIOV. > > > > > (e.g. SIOV/SRIOV backward compatibility case) > > > > > > > > > > The upper layer stack could use this interface as the last step to check > > > > > if one device is able to migrate to another device before triggering a real > > > > > live migration procedure. > > > > > we are not sure if this interface is of value or help to you. please don't > > > > > hesitate to drop your valuable comments. > > > > > > > > > > > > > > > (1) interface definition > > > > > The interface is defined in below way: > > > > > > > > > > __ userspace > > > > > /\ \ > > > > > / \write > > > > > / read \ > > > > > ________/__________ ___\|/_____________ > > > > > | migration_version | | migration_version |-->check migration > > > > > --------------------- --------------------- compatibility > > > > > device A device B > > > > > > > > > > > > > > > a device attribute named migration_version is defined under each device's > > > > > sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). > > > > > userspace tools read the migration_version as a string from the source device, > > > > > and write it to the migration_version sysfs attribute in the target device. > > > > > > > > > > The userspace should treat ANY of below conditions as two devices not compatible: > > > > > - any one of the two devices does not have a migration_version attribute > > > > > - error when reading from migration_version attribute of one device > > > > > - error when writing migration_version string of one device to > > > > > migration_version attribute of the other device > > > > > > > > > > The string read from migration_version attribute is defined by device vendor > > > > > driver and is completely opaque to the userspace. > > > > > for a Intel vGPU, string format can be defined like > > > > > "parent device PCI ID" + "version of gvt driver" + "mdev type" + "aggregator count". > > > > > > > > > > for an NVMe VF connecting to a remote storage. it could be > > > > > "PCI ID" + "driver version" + "configured remote storage URL" > > > > > > > > > > for a QAT VF, it may be > > > > > "PCI ID" + "driver version" + "supported encryption set". > > > > > > > > > > (to avoid namespace confliction from each vendor, we may prefix a driver name to > > > > > each migration_version string. e.g. i915-v1-8086-591d-i915-GVTg_V5_8-1) > > > > > > It's very strange to define it as opaque and then proceed to describe > > > the contents of that opaque string. The point is that its contents > > > are defined by the vendor driver to describe the device, driver version, > > > and possibly metadata about the configuration of the device. One > > > instance of a device might generate a different string from another. > > > The string that a device produces is not necessarily the only string > > > the vendor driver will accept, for example the driver might support > > > backwards compatible migrations. > > > > (As I've said in the previous discussion, off one of the patch series) > > > > My view is it makes sense to have a half-way house on the opaqueness of > > this string; I'd expect to have an ID and version that are human > > readable, maybe a device ID/name that's human interpretable and then a > > bunch of other cruft that maybe device/vendor/version specific. > > > > I'm thinking that we want to be able to report problems and include the > > string and the user to be able to easily identify the device that was > > complaining and notice a difference in versions, and perhaps also use > > it in compatibility patterns to find compatible hosts; but that does > > get tricky when it's a 'ask the device if it's compatible'. > > In the reply I just sent to Dan, I gave this example of what a > "compatibility string" might look like represented as json: > > { > "device_api": "vfio-pci", > "vendor": "vendor-driver-name", > "version": { > "major": 0, > "minor": 1 > }, > "vfio-pci": { // Based on above device_api > "vendor": 0x1234, // Values for the exposed device > "device": 0x5678, > // Possibly further parameters for a more specific match > }, > "mdev_attrs": [ > { "attribute0": "VALUE" } > ] > } > > Are you thinking that we might allow the vendor to include a vendor > specific array where we'd simply require that both sides have matching > fields and values? ie. > > "vendor_fields": [ > { "unknown_field0": "unknown_value0" }, > { "unknown_field1": "unknown_value1" }, > ] > > We could certainly make that part of the spec, but I can't really > figure the value of it other than to severely restrict compatibility, > which the vendor could already do via the version.major value. Maybe > they'd want to put a build timestamp, random uuid, or source sha1 into > such a field to make absolutely certain compatibility is only determined > between identical builds? Thanks, > Yes, I agree kernel could expose such sysfs interface to educate openstack how to filter out devices. But I still think the proposed migration_version (or rename to migration_compatibility) interface is still required for libvirt to do double check. In the following scenario: 1. openstack chooses the target device by reading sysfs interface (of json format) of the source device. And Openstack are now pretty sure the two devices are migration compatible. 2. openstack asks libvirt to create the target VM with the target device and start live migration. 3. libvirt now receives the request. so it now has two choices: (1) create the target VM & target device and start live migration directly (2) double check if the target device is compatible with the source device before doing the remaining tasks. Because the factors to determine whether two devices are live migration compatible are complicated and may be dynamically changing, (e.g. driver upgrade or configuration changes), and also because libvirt should not totally rely on the input from openstack, I think the cost for libvirt is relatively lower if it chooses to go (2) than (1). At least it has no need to cancel migration and destroy the VM if it knows it earlier.

So, it means the kernel may need to expose two parallel interfaces: (1) with json format, enumerating all possible fields and comparing methods, so as to indicate openstack how to find a matching target device (2) an opaque driver defined string, requiring write and test in target, which is used by libvirt to make sure device compatibility, rather than rely on the input accurateness from openstack or rely on kernel driver implementing the compatibility detection immediately after migration start. Does it make sense? Thanks Yan

On 2020/7/14 上午7:29, Yan Zhao wrote: > hi folks, > we are defining a device migration compatibility interface that helps upper > layer stack like openstack/ovirt/libvirt to check if two devices are > live migration compatible. > The "devices" here could be MDEVs, physical devices, or hybrid of the two. > e.g. we could use it to check whether > - a src MDEV can migrate to a target MDEV, > - a src VF in SRIOV can migrate to a target VF in SRIOV, > - a src MDEV can migration to a target VF in SRIOV. > (e.g. SIOV/SRIOV backward compatibility case) > > The upper layer stack could use this interface as the last step to check > if one device is able to migrate to another device before triggering a real > live migration procedure. > we are not sure if this interface is of value or help to you. please don't > hesitate to drop your valuable comments. > > > (1) interface definition > The interface is defined in below way: > > __ userspace > /\ \ > / \write > / read \ > ________/__________ ___\|/_____________ > | migration_version | | migration_version |-->check migration > --------------------- --------------------- compatibility > device A device B > > > a device attribute named migration_version is defined under each device's > sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). Are you aware of the devlink based device management interface that is proposed upstream? I think it has many advantages over sysfs, do you consider to switch to that?

> userspace tools read the migration_version as a string from the source device, > and write it to the migration_version sysfs attribute in the target device. > > The userspace should treat ANY of below conditions as two devices not compatible: > - any one of the two devices does not have a migration_version attribute > - error when reading from migration_version attribute of one device > - error when writing migration_version string of one device to > migration_version attribute of the other device > > The string read from migration_version attribute is defined by device vendor > driver and is completely opaque to the userspace. My understanding is that something opaque to userspace is not the philosophy

of Linux. Instead of having a generic API but opaque value, why not do in a vendor specific way like: 1) exposing the device capability in a vendor specific way via sysfs/devlink or other API 2) management read capability in both src and dst and determine whether we can do the migration This is the way we plan to do with vDPA.

On Tue, Jul 14, 2020 at 02:59:48PM -0600, Alex Williamson wrote: > On Tue, 14 Jul 2020 18:19:46 +0100 > "Dr. David Alan Gilbert" <dgilbert(a)redhat.com&gt; wrote: > > > * Alex Williamson (alex.williamson(a)redhat.com) wrote: > > > On Tue, 14 Jul 2020 11:21:29 +0100 > > > Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > > > > > > > On Tue, Jul 14, 2020 at 07:29:57AM +0800, Yan Zhao wrote: > > > > > hi folks, > > > > > we are defining a device migration compatibility interface that helps upper > > > > > layer stack like openstack/ovirt/libvirt to check if two devices are > > > > > live migration compatible. > > > > > The "devices" here could be MDEVs, physical devices, or hybrid of the two. > > > > > e.g. we could use it to check whether > > > > > - a src MDEV can migrate to a target MDEV, > > > > > - a src VF in SRIOV can migrate to a target VF in SRIOV, > > > > > - a src MDEV can migration to a target VF in SRIOV. > > > > > (e.g. SIOV/SRIOV backward compatibility case) > > > > > > > > > > The upper layer stack could use this interface as the last step to check > > > > > if one device is able to migrate to another device before triggering a real > > > > > live migration procedure. > > > > > we are not sure if this interface is of value or help to you. please don't > > > > > hesitate to drop your valuable comments. > > > > > > > > > > > > > > > (1) interface definition > > > > > The interface is defined in below way: > > > > > > > > > > __ userspace > > > > > /\ \ > > > > > / \write > > > > > / read \ > > > > > ________/__________ ___\|/_____________ > > > > > | migration_version | | migration_version |-->check migration > > > > > --------------------- --------------------- compatibility > > > > > device A device B > > > > > > > > > > > > > > > a device attribute named migration_version is defined under each device's > > > > > sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). > > > > > userspace tools read the migration_version as a string from the source device, > > > > > and write it to the migration_version sysfs attribute in the target device. > > > > > > > > > > The userspace should treat ANY of below conditions as two devices not compatible: > > > > > - any one of the two devices does not have a migration_version attribute > > > > > - error when reading from migration_version attribute of one device > > > > > - error when writing migration_version string of one device to > > > > > migration_version attribute of the other device > > > > > > > > > > The string read from migration_version attribute is defined by device vendor > > > > > driver and is completely opaque to the userspace. > > > > > for a Intel vGPU, string format can be defined like > > > > > "parent device PCI ID" + "version of gvt driver" + "mdev type" + "aggregator count". > > > > > > > > > > for an NVMe VF connecting to a remote storage. it could be > > > > > "PCI ID" + "driver version" + "configured remote storage URL" > > > > > > > > > > for a QAT VF, it may be > > > > > "PCI ID" + "driver version" + "supported encryption set". > > > > > > > > > > (to avoid namespace confliction from each vendor, we may prefix a driver name to > > > > > each migration_version string. e.g. i915-v1-8086-591d-i915-GVTg_V5_8-1) > > > > > > It's very strange to define it as opaque and then proceed to describe > > > the contents of that opaque string. The point is that its contents > > > are defined by the vendor driver to describe the device, driver version, > > > and possibly metadata about the configuration of the device. One > > > instance of a device might generate a different string from another. > > > The string that a device produces is not necessarily the only string > > > the vendor driver will accept, for example the driver might support > > > backwards compatible migrations. > > > > (As I've said in the previous discussion, off one of the patch series) > > > > My view is it makes sense to have a half-way house on the opaqueness of > > this string; I'd expect to have an ID and version that are human > > readable, maybe a device ID/name that's human interpretable and then a > > bunch of other cruft that maybe device/vendor/version specific. > > > > I'm thinking that we want to be able to report problems and include the > > string and the user to be able to easily identify the device that was > > complaining and notice a difference in versions, and perhaps also use > > it in compatibility patterns to find compatible hosts; but that does > > get tricky when it's a 'ask the device if it's compatible'. > > In the reply I just sent to Dan, I gave this example of what a > "compatibility string" might look like represented as json: > > { > "device_api": "vfio-pci", > "vendor": "vendor-driver-name", > "version": { > "major": 0, > "minor": 1 > }, > "vfio-pci": { // Based on above device_api > "vendor": 0x1234, // Values for the exposed device > "device": 0x5678, > // Possibly further parameters for a more specific match > }, > "mdev_attrs": [ > { "attribute0": "VALUE" } > ] > } > > Are you thinking that we might allow the vendor to include a vendor > specific array where we'd simply require that both sides have matching > fields and values? ie. > > "vendor_fields": [ > { "unknown_field0": "unknown_value0" }, > { "unknown_field1": "unknown_value1" }, > ] > > We could certainly make that part of the spec, but I can't really > figure the value of it other than to severely restrict compatibility, > which the vendor could already do via the version.major value. Maybe > they'd want to put a build timestamp, random uuid, or source sha1 into > such a field to make absolutely certain compatibility is only determined > between identical builds? Thanks, > Yes, I agree kernel could expose such sysfs interface to educate openstack how to filter out devices. But I still think the proposed migration_version (or rename to migration_compatibility) interface is still required for libvirt to do double check. In the following scenario: 1. openstack chooses the target device by reading sysfs interface (of json format) of the source device. And Openstack are now pretty sure the two devices are migration compatible. 2. openstack asks libvirt to create the target VM with the target device and start live migration. 3. libvirt now receives the request. so it now has two choices: (1) create the target VM & target device and start live migration directly (2) double check if the target device is compatible with the source device before doing the remaining tasks. Because the factors to determine whether two devices are live migration compatible are complicated and may be dynamically changing, (e.g. driver upgrade or configuration changes), and also because libvirt should not totally rely on the input from openstack, I think the cost for libvirt is relatively lower if it chooses to go (2) than (1). At least it has no need to cancel migration and destroy the VM if it knows it earlier. So, it means the kernel may need to expose two parallel interfaces: (1) with json format, enumerating all possible fields and comparing methods, so as to indicate openstack how to find a matching target device (2) an opaque driver defined string, requiring write and test in target, which is used by libvirt to make sure device compatibility, rather than rely on the input accurateness from openstack or rely on kernel driver implementing the compatibility detection immediately after migration start. Does it make sense?

On Thu, Jul 16, 2020 at 12:16:26PM +0800, Jason Wang wrote: > > On 2020/7/14 上午7:29, Yan Zhao wrote: > > hi folks, > > we are defining a device migration compatibility interface that helps upper > > layer stack like openstack/ovirt/libvirt to check if two devices are > > live migration compatible. > > The "devices" here could be MDEVs, physical devices, or hybrid of the two. > > e.g. we could use it to check whether > > - a src MDEV can migrate to a target MDEV, > > - a src VF in SRIOV can migrate to a target VF in SRIOV, > > - a src MDEV can migration to a target VF in SRIOV. > > (e.g. SIOV/SRIOV backward compatibility case) > > > > The upper layer stack could use this interface as the last step to check > > if one device is able to migrate to another device before triggering a real > > live migration procedure. > > we are not sure if this interface is of value or help to you. please don't > > hesitate to drop your valuable comments. > > > > > > (1) interface definition > > The interface is defined in below way: > > > > __ userspace > > /\ \ > > / \write > > / read \ > > ________/__________ ___\|/_____________ > > | migration_version | | migration_version |-->check migration > > --------------------- --------------------- compatibility > > device A device B > > > > > > a device attribute named migration_version is defined under each device's > > sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). > > > Are you aware of the devlink based device management interface that is > proposed upstream? I think it has many advantages over sysfs, do you > consider to switch to that?

not familiar with the devlink. will do some research of it. > > > > userspace tools read the migration_version as a string from the source device, > > and write it to the migration_version sysfs attribute in the target device. > > > > The userspace should treat ANY of below conditions as two devices not compatible: > > - any one of the two devices does not have a migration_version attribute > > - error when reading from migration_version attribute of one device > > - error when writing migration_version string of one device to > > migration_version attribute of the other device > > > > The string read from migration_version attribute is defined by device vendor > > driver and is completely opaque to the userspace. > > > My understanding is that something opaque to userspace is not the philosophy but the VFIO live migration in itself is essentially a big opaque stream to userspace. > of Linux. Instead of having a generic API but opaque value, why not do in a > vendor specific way like: > > 1) exposing the device capability in a vendor specific way via sysfs/devlink > or other API > 2) management read capability in both src and dst and determine whether we > can do the migration > > This is the way we plan to do with vDPA. > yes, in another reply, Alex proposed to use an interface in json format. I guess we can define something like { "self" : [ { "pciid" : "8086591d", "driver" : "i915", "gvt-version" : "v1", "mdev_type" : "i915-GVTg_V5_2", "aggregator" : "1", "pv-mode" : "none", } ], "compatible" : [ { "pciid" : "8086591d", "driver" : "i915", "gvt-version" : "v1", "mdev_type" : "i915-GVTg_V5_2", "aggregator" : "1" "pv-mode" : "none", }, { "pciid" : "8086591d", "driver" : "i915", "gvt-version" : "v1", "mdev_type" : "i915-GVTg_V5_4", "aggregator" : "2" "pv-mode" : "none", }, { "pciid" : "8086591d", "driver" : "i915", "gvt-version" : "v2", "mdev_type" : "i915-GVTg_V5_4", "aggregator" : "2" "pv-mode" : "none, ppgtt, context", } ... ] } But as those fields are mostly vendor specific, the userspace can only do simple string comparing, I guess the list would be very long as it needs to enumerate all possible targets.

also, in some fileds like "gvt-version", is there a simple way to express things like v2+?

If the userspace can read this interface both in src and target and check whether both src and target are in corresponding compatible list, I think it will work for us. But still, kernel should not rely on userspace's choice, the opaque compatibility string is still required in kernel. No matter whether it would be exposed to userspace as an compatibility checking interface, vendor driver would keep this part of code and embed the string into the migration stream. so exposing it as an interface to be used by libvirt to do a safety check before a real live migration is only about enabling the kernel part of check to happen ahead.

* Alex Williamson (alex.williamson(a)redhat.com) wrote: > On Wed, 15 Jul 2020 16:20:41 +0800 > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > On Tue, Jul 14, 2020 at 02:59:48PM -0600, Alex Williamson wrote: > > > On Tue, 14 Jul 2020 18:19:46 +0100 > > > "Dr. David Alan Gilbert" <dgilbert(a)redhat.com&gt; wrote: > > > > > > > * Alex Williamson (alex.williamson(a)redhat.com) wrote: > > > > > On Tue, 14 Jul 2020 11:21:29 +0100 > > > > > Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > > > > > > > > > > > On Tue, Jul 14, 2020 at 07:29:57AM +0800, Yan Zhao wrote: > > > > > > > hi folks, > > > > > > > we are defining a device migration compatibility interface that helps upper > > > > > > > layer stack like openstack/ovirt/libvirt to check if two devices are > > > > > > > live migration compatible. > > > > > > > The "devices" here could be MDEVs, physical devices, or hybrid of the two. > > > > > > > e.g. we could use it to check whether > > > > > > > - a src MDEV can migrate to a target MDEV, > > > > > > > - a src VF in SRIOV can migrate to a target VF in SRIOV, > > > > > > > - a src MDEV can migration to a target VF in SRIOV. > > > > > > > (e.g. SIOV/SRIOV backward compatibility case) > > > > > > > > > > > > > > The upper layer stack could use this interface as the last step to check > > > > > > > if one device is able to migrate to another device before triggering a real > > > > > > > live migration procedure. > > > > > > > we are not sure if this interface is of value or help to you. please don't > > > > > > > hesitate to drop your valuable comments. > > > > > > > > > > > > > > > > > > > > > (1) interface definition > > > > > > > The interface is defined in below way: > > > > > > > > > > > > > > __ userspace > > > > > > > /\ \ > > > > > > > / \write > > > > > > > / read \ > > > > > > > ________/__________ ___\|/_____________ > > > > > > > | migration_version | | migration_version |-->check migration > > > > > > > --------------------- --------------------- compatibility > > > > > > > device A device B > > > > > > > > > > > > > > > > > > > > > a device attribute named migration_version is defined under each device's > > > > > > > sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). > > > > > > > userspace tools read the migration_version as a string from the source device, > > > > > > > and write it to the migration_version sysfs attribute in the target device. > > > > > > > > > > > > > > The userspace should treat ANY of below conditions as two devices not compatible: > > > > > > > - any one of the two devices does not have a migration_version attribute > > > > > > > - error when reading from migration_version attribute of one device > > > > > > > - error when writing migration_version string of one device to > > > > > > > migration_version attribute of the other device > > > > > > > > > > > > > > The string read from migration_version attribute is defined by device vendor > > > > > > > driver and is completely opaque to the userspace. > > > > > > > for a Intel vGPU, string format can be defined like > > > > > > > "parent device PCI ID" + "version of gvt driver" + "mdev type" + "aggregator count". > > > > > > > > > > > > > > for an NVMe VF connecting to a remote storage. it could be > > > > > > > "PCI ID" + "driver version" + "configured remote storage URL" > > > > > > > > > > > > > > for a QAT VF, it may be > > > > > > > "PCI ID" + "driver version" + "supported encryption set". > > > > > > > > > > > > > > (to avoid namespace confliction from each vendor, we may prefix a driver name to > > > > > > > each migration_version string. e.g. i915-v1-8086-591d-i915-GVTg_V5_8-1) > > > > > > > > > > It's very strange to define it as opaque and then proceed to describe > > > > > the contents of that opaque string. The point is that its contents > > > > > are defined by the vendor driver to describe the device, driver version, > > > > > and possibly metadata about the configuration of the device. One > > > > > instance of a device might generate a different string from another. > > > > > The string that a device produces is not necessarily the only string > > > > > the vendor driver will accept, for example the driver might support > > > > > backwards compatible migrations. > > > > > > > > (As I've said in the previous discussion, off one of the patch series) > > > > > > > > My view is it makes sense to have a half-way house on the opaqueness of > > > > this string; I'd expect to have an ID and version that are human > > > > readable, maybe a device ID/name that's human interpretable and then a > > > > bunch of other cruft that maybe device/vendor/version specific. > > > > > > > > I'm thinking that we want to be able to report problems and include the > > > > string and the user to be able to easily identify the device that was > > > > complaining and notice a difference in versions, and perhaps also use > > > > it in compatibility patterns to find compatible hosts; but that does > > > > get tricky when it's a 'ask the device if it's compatible'. > > > > > > In the reply I just sent to Dan, I gave this example of what a > > > "compatibility string" might look like represented as json: > > > > > > { > > > "device_api": "vfio-pci", > > > "vendor": "vendor-driver-name", > > > "version": { > > > "major": 0, > > > "minor": 1 > > > }, > > > "vfio-pci": { // Based on above device_api > > > "vendor": 0x1234, // Values for the exposed device > > > "device": 0x5678, > > > // Possibly further parameters for a more specific match > > > }, > > > "mdev_attrs": [ > > > { "attribute0": "VALUE" } > > > ] > > > } > > > > > > Are you thinking that we might allow the vendor to include a vendor > > > specific array where we'd simply require that both sides have matching > > > fields and values? ie. > > > > > > "vendor_fields": [ > > > { "unknown_field0": "unknown_value0" }, > > > { "unknown_field1": "unknown_value1" }, > > > ] > > > > > > We could certainly make that part of the spec, but I can't really > > > figure the value of it other than to severely restrict compatibility, > > > which the vendor could already do via the version.major value. Maybe > > > they'd want to put a build timestamp, random uuid, or source sha1 into > > > such a field to make absolutely certain compatibility is only determined > > > between identical builds? Thanks, > > > > > Yes, I agree kernel could expose such sysfs interface to educate > > openstack how to filter out devices. But I still think the proposed > > migration_version (or rename to migration_compatibility) interface is > > still required for libvirt to do double check. > > > > In the following scenario: > > 1. openstack chooses the target device by reading sysfs interface (of json > > format) of the source device. And Openstack are now pretty sure the two > > devices are migration compatible. > > 2. openstack asks libvirt to create the target VM with the target device > > and start live migration. > > 3. libvirt now receives the request. so it now has two choices: > > (1) create the target VM & target device and start live migration directly > > (2) double check if the target device is compatible with the source > > device before doing the remaining tasks. > > > > Because the factors to determine whether two devices are live migration > > compatible are complicated and may be dynamically changing, (e.g. driver > > upgrade or configuration changes), and also because libvirt should not > > totally rely on the input from openstack, I think the cost for libvirt is > > relatively lower if it chooses to go (2) than (1). At least it has no > > need to cancel migration and destroy the VM if it knows it earlier. > > > > So, it means the kernel may need to expose two parallel interfaces: > > (1) with json format, enumerating all possible fields and comparing > > methods, so as to indicate openstack how to find a matching target device > > (2) an opaque driver defined string, requiring write and test in target, > > which is used by libvirt to make sure device compatibility, rather than > > rely on the input accurateness from openstack or rely on kernel driver > > implementing the compatibility detection immediately after migration > > start. > > > > Does it make sense? > > No, libvirt is not responsible for the success or failure of the > migration, it's the vendor driver's responsibility to encode > compatibility information early in the migration stream and error > should the incoming device prove to be incompatible. It's not > libvirt's job to second guess the management engine and I would not > support a duplicate interface only for that purpose. Thanks, libvirt does try to enforce it for other things; trying to stop a bad migration from starting.

On 2020/7/18 上午12:12, Alex Williamson wrote: > On Thu, 16 Jul 2020 16:32:30 +0800 > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > On Thu, Jul 16, 2020 at 12:16:26PM +0800, Jason Wang wrote: > > > On 2020/7/14 上午7:29, Yan Zhao wrote: > > > > hi folks, > > > > we are defining a device migration compatibility interface that helps upper > > > > layer stack like openstack/ovirt/libvirt to check if two devices are > > > > live migration compatible. > > > > The "devices" here could be MDEVs, physical devices, or hybrid of the two. > > > > e.g. we could use it to check whether > > > > - a src MDEV can migrate to a target MDEV, > > > > - a src VF in SRIOV can migrate to a target VF in SRIOV, > > > > - a src MDEV can migration to a target VF in SRIOV. > > > > (e.g. SIOV/SRIOV backward compatibility case) > > > > > > > > The upper layer stack could use this interface as the last step to check > > > > if one device is able to migrate to another device before triggering a real > > > > live migration procedure. > > > > we are not sure if this interface is of value or help to you. please don't > > > > hesitate to drop your valuable comments. > > > > > > > > > > > > (1) interface definition > > > > The interface is defined in below way: > > > > > > > > __ userspace > > > > /\ \ > > > > / \write > > > > / read \ > > > > ________/__________ ___\|/_____________ > > > > | migration_version | | migration_version |-->check migration > > > > --------------------- --------------------- compatibility > > > > device A device B > > > > > > > > > > > > a device attribute named migration_version is defined under each device's > > > > sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). > > > > > > Are you aware of the devlink based device management interface that is > > > proposed upstream? I think it has many advantages over sysfs, do you > > > consider to switch to that? > > Advantages, such as? My understanding for devlink(netlink) over sysfs (some are mentioned at the time of vDPA sysfs mgmt API discussion) are:

- existing users (NIC, crypto, SCSI, ib), mature and stable - much better error reporting (ext_ack other than string or errno) - namespace aware - do not couple with kobject Thanks

On Mon, 2020-07-20 at 11:41 +0800, Jason Wang wrote: > On 2020/7/18 上午12:12, Alex Williamson wrote: >> On Thu, 16 Jul 2020 16:32:30 +0800 >> Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: >> >>> On Thu, Jul 16, 2020 at 12:16:26PM +0800, Jason Wang wrote: >>>> On 2020/7/14 上午7:29, Yan Zhao wrote: >>>>> hi folks, >>>>> we are defining a device migration compatibility interface that helps upper >>>>> layer stack like openstack/ovirt/libvirt to check if two devices are >>>>> live migration compatible. >>>>> The "devices" here could be MDEVs, physical devices, or hybrid of the two. >>>>> e.g. we could use it to check whether >>>>> - a src MDEV can migrate to a target MDEV, >>>>> - a src VF in SRIOV can migrate to a target VF in SRIOV, >>>>> - a src MDEV can migration to a target VF in SRIOV. >>>>> (e.g. SIOV/SRIOV backward compatibility case) >>>>> >>>>> The upper layer stack could use this interface as the last step to check >>>>> if one device is able to migrate to another device before triggering a real >>>>> live migration procedure. >>>>> we are not sure if this interface is of value or help to you. please don't >>>>> hesitate to drop your valuable comments. >>>>> >>>>> >>>>> (1) interface definition >>>>> The interface is defined in below way: >>>>> >>>>> __ userspace >>>>> /\ \ >>>>> / \write >>>>> / read \ >>>>> ________/__________ ___\|/_____________ >>>>> | migration_version | | migration_version |-->check migration >>>>> --------------------- --------------------- compatibility >>>>> device A device B >>>>> >>>>> >>>>> a device attribute named migration_version is defined under each device's >>>>> sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). >>>> Are you aware of the devlink based device management interface that is >>>> proposed upstream? I think it has many advantages over sysfs, do you >>>> consider to switch to that? >> Advantages, such as? > > My understanding for devlink(netlink) over sysfs (some are mentioned at > the time of vDPA sysfs mgmt API discussion) are: i tought netlink was used more a as a configuration protocoal to qurry and confire nic and i guess other devices in its devlink form requireint a tool to be witten that can speak the protocal to interact with. the primary advantate of sysfs is that everything is just a file. there are no addtional depleenceis needed

and unlike netlink there are not interoperatblity issues in a coanitnerised env. if you are using diffrenet version of libc and gcc in the contaienr vs the host my understanding is tools like ethtool from ubuntu deployed in a container on a centos host can have issue communicating with the host kernel.

if its jsut a file unless the format the data is returnin in chagnes or the layout of sysfs changes its compatiable regardless of what you use to read it.

> - existing users (NIC, crypto, SCSI, ib), mature and stable > - much better error reporting (ext_ack other than string or errno) > - namespace aware > - do not couple with kobject > > Thanks >

> > As you indicate, the vendor driver is responsible for checking version > > information embedded within the migration stream. Therefore a > > migration should fail early if the devices are incompatible. Is it > but as I know, currently in VFIO migration protocol, we have no way to > get vendor specific compatibility checking string in migration setup stage > (i.e. .save_setup stage) before the device is set to _SAVING state. > In this way, for devices who does not save device data in precopy stage, > the migration compatibility checking is as late as in stop-and-copy > stage, which is too late. > do you think we need to add the getting/checking of vendor specific > compatibility string early in save_setup stage? > hi Alex, after an offline discussion with Kevin, I realized that it may not be a problem if migration compatibility check in vendor driver occurs late in stop-and-copy phase for some devices, because if we report device compatibility attributes clearly in an interface, the chances for libvirt/openstack to make a wrong decision is little.

so, do you think we are now arriving at an agreement that we'll give up the read-and-test scheme and start to defining one interface (perhaps in json format), from which libvirt/openstack is able to parse and find out compatibility list of a source mdev/physical device?

On Mon, Jul 27, 2020 at 04:23:21PM -0600, Alex Williamson wrote: > On Mon, 27 Jul 2020 15:24:40 +0800 > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > > > As you indicate, the vendor driver is responsible for checking version > > > > information embedded within the migration stream. Therefore a > > > > migration should fail early if the devices are incompatible. Is it > > > > > > but as I know, currently in VFIO migration protocol, we have no way to > > > get vendor specific compatibility checking string in migration setup stage > > > (i.e. .save_setup stage) before the device is set to _SAVING state. > > > In this way, for devices who does not save device data in precopy stage, > > > the migration compatibility checking is as late as in stop-and-copy > > > stage, which is too late. > > > do you think we need to add the getting/checking of vendor specific > > > compatibility string early in save_setup stage? > > > > > > > hi Alex, > > after an offline discussion with Kevin, I realized that it may not be a > > problem if migration compatibility check in vendor driver occurs late in > > stop-and-copy phase for some devices, because if we report device > > compatibility attributes clearly in an interface, the chances for > > libvirt/openstack to make a wrong decision is little. > > I think it would be wise for a vendor driver to implement a pre-copy > phase, even if only to send version information and verify it at the > target. Deciding you have no device state to send during pre-copy does > not mean your vendor driver needs to opt-out of the pre-copy phase > entirely. Please also note that pre-copy is at the user's discretion, > we've defined that we can enter stop-and-copy at any point, including > without a pre-copy phase, so I would recommend that vendor drivers > validate compatibility at the start of both the pre-copy and the > stop-and-copy phases. > ok. got it! > > so, do you think we are now arriving at an agreement that we'll give up > > the read-and-test scheme and start to defining one interface (perhaps in > > json format), from which libvirt/openstack is able to parse and find out > > compatibility list of a source mdev/physical device? > > Based on the feedback we've received, the previously proposed interface > is not viable. I think there's agreement that the user needs to be > able to parse and interpret the version information. Using json seems > viable, but I don't know if it's the best option. Is there any > precedent of markup strings returned via sysfs we could follow? I found some examples of using formatted string under /sys, mostly under tracing. maybe we can do a similar implementation. #cat /sys/kernel/debug/tracing/events/kvm/kvm_mmio/format name: kvm_mmio ID: 32 format: field:unsigned short common_type; offset:0; size:2; signed:0; field:unsigned char common_flags; offset:2; size:1; signed:0; field:unsigned char common_preempt_count; offset:3; size:1; signed:0; field:int common_pid; offset:4; size:4; signed:1; field:u32 type; offset:8; size:4; signed:0; field:u32 len; offset:12; size:4; signed:0; field:u64 gpa; offset:16; size:8; signed:0; field:u64 val; offset:24; size:8; signed:0; print fmt: "mmio %s len %u gpa 0x%llx val 0x%llx", __print_symbolic(REC->type, { 0, "unsatisfied-read" }, { 1, "read" }, { 2, "write" }), REC->len, REC->gpa, REC->val

#cat /sys/devices/pci0000:00/0000:00:02.0/uevent DRIVER=vfio-pci PCI_CLASS=30000 PCI_ID=8086:591D PCI_SUBSYS_ID=8086:2212 PCI_SLOT_NAME=0000:00:02.0 MODALIAS=pci:v00008086d0000591Dsv00008086sd00002212bc03sc00i00

> > Your idea of having both a "self" object and an array of "compatible" > objects is perhaps something we can build on, but we must not assume > PCI devices at the root level of the object. Providing both the > mdev-type and the driver is a bit redundant, since the former includes > the latter. We can't have vendor specific versioning schemes though, > ie. gvt-version. We need to agree on a common scheme and decide which > fields the version is relative to, ex. just the mdev type? what about making all comparing fields vendor specific? userspace like openstack only needs to parse and compare if target device is within source compatible list without understanding the meaning of each field.

> I had also proposed fields that provide information to create a > compatible type, for example to create a type_x2 device from a type_x1 > mdev type, they need to know to apply an aggregation attribute. If we > need to explicitly list every aggregation value and the resulting type, > I think we run aground of what aggregation was trying to avoid anyway, > so we might need to pick a language that defines variable substitution > or some kind of tagging. For example if we could define ${aggr} as an > integer within a specified range, then we might be able to define a type > relative to that value (type_x${aggr}) which requires an aggregation > attribute using the same value. I dunno, just spit balling. Thanks, what about a migration_compatible attribute under device node like below?

#cat /sys/bus/pci/devices/0000\:00\:02.0/UUID1/migration_compatible SELF: device_type=pci device_id=8086591d mdev_type=i915-GVTg_V5_2 aggregator=1 pv_mode="none+ppgtt+context" interface_version=3 COMPATIBLE: device_type=pci device_id=8086591d mdev_type=i915-GVTg_V5_{val1:int:1,2,4,8}

aggregator={val1}/2 pv_mode={val2:string:"none+ppgtt","none+context","none+ppgtt+context"} interface_version={val3:int:2,3} COMPATIBLE: device_type=pci device_id=8086591d mdev_type=i915-GVTg_V5_{val1:int:1,2,4,8} aggregator={val1}/2 pv_mode="" #"" meaning empty, could be absent in a compatible device interface_version=1

#cat /sys/bus/pci/dei915-GVTg_V5_{val1:int:1,2,4,8}vices/0000\:00\:i915- GVTg_V5_{val1:int:1,2,4,8}2.0/UUID2/migration_compatible SELF: device_type=pci device_id=8086591d mdev_type=i915-GVTg_V5_4 aggregator=2 interface_version=1 COMPATIBLE: device_type=pci device_id=8086591d mdev_type=i915-GVTg_V5_{val1:int:1,2,4,8} aggregator={val1}/2 interface_version=1

Notes: - A COMPATIBLE object is a line starting with COMPATIBLE. It specifies a list of compatible devices that are allowed to migrate in. The reason to allow multiple COMPATIBLE objects is that when it is hard to express a complex compatible logic in one COMPATIBLE object, a simple enumeration is still a fallback. in the above example, device UUID2 is in the compatible list of device UUID1, but device UUID1 is not in the compatible list of device UUID2, so device UUID2 is able to migrate to device UUID1, but device UUID1 is not able to migrate to device UUID2. - fields under each object are of "and" relationship to each other, meaning all fields of SELF object of a target device must be equal to corresponding fields of a COMPATIBLE object of source device, otherwise it is regarded as not compatible. - each field, however, is able to specify multiple allowed values, using variables as explained below. - variables are represented with {}, the first appearance of one variable specifies its type and allowed list. e.g. {val1:int:1,2,4,8} represents var1 whose type is integer and allowed values are 1, 2, 4, 8. - vendors are able to specify which fields are within the comparing list and which fields are not. e.g. for physical VF migration, it may not choose mdev_type as a comparing field, and maybe use driver name instead.

Thanks Yan

On Wed, 2020-07-29 at 16:05 +0800, Yan Zhao wrote: > On Mon, Jul 27, 2020 at 04:23:21PM -0600, Alex Williamson wrote: > > On Mon, 27 Jul 2020 15:24:40 +0800 > > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > > > > > As you indicate, the vendor driver is responsible for checking version > > > > > information embedded within the migration stream. Therefore a > > > > > migration should fail early if the devices are incompatible. Is it > > > > > > > > but as I know, currently in VFIO migration protocol, we have no way to > > > > get vendor specific compatibility checking string in migration setup stage > > > > (i.e. .save_setup stage) before the device is set to _SAVING state. > > > > In this way, for devices who does not save device data in precopy stage, > > > > the migration compatibility checking is as late as in stop-and-copy > > > > stage, which is too late. > > > > do you think we need to add the getting/checking of vendor specific > > > > compatibility string early in save_setup stage? > > > > > > > > > > hi Alex, > > > after an offline discussion with Kevin, I realized that it may not be a > > > problem if migration compatibility check in vendor driver occurs late in > > > stop-and-copy phase for some devices, because if we report device > > > compatibility attributes clearly in an interface, the chances for > > > libvirt/openstack to make a wrong decision is little. > > > > I think it would be wise for a vendor driver to implement a pre-copy > > phase, even if only to send version information and verify it at the > > target. Deciding you have no device state to send during pre-copy does > > not mean your vendor driver needs to opt-out of the pre-copy phase > > entirely. Please also note that pre-copy is at the user's discretion, > > we've defined that we can enter stop-and-copy at any point, including > > without a pre-copy phase, so I would recommend that vendor drivers > > validate compatibility at the start of both the pre-copy and the > > stop-and-copy phases. > > > > ok. got it! > > > > so, do you think we are now arriving at an agreement that we'll give up > > > the read-and-test scheme and start to defining one interface (perhaps in > > > json format), from which libvirt/openstack is able to parse and find out > > > compatibility list of a source mdev/physical device? > > > > Based on the feedback we've received, the previously proposed interface > > is not viable. I think there's agreement that the user needs to be > > able to parse and interpret the version information. Using json seems > > viable, but I don't know if it's the best option. Is there any > > precedent of markup strings returned via sysfs we could follow? > > I found some examples of using formatted string under /sys, mostly under > tracing. maybe we can do a similar implementation. > > #cat /sys/kernel/debug/tracing/events/kvm/kvm_mmio/format > > name: kvm_mmio > ID: 32 > format: > field:unsigned short common_type; offset:0; size:2; signed:0; > field:unsigned char common_flags; offset:2; size:1; signed:0; > field:unsigned char common_preempt_count; offset:3; size:1; signed:0; > field:int common_pid; offset:4; size:4; signed:1; > > field:u32 type; offset:8; size:4; signed:0; > field:u32 len; offset:12; size:4; signed:0; > field:u64 gpa; offset:16; size:8; signed:0; > field:u64 val; offset:24; size:8; signed:0; > > print fmt: "mmio %s len %u gpa 0x%llx val 0x%llx", __print_symbolic(REC->type, { 0, "unsatisfied-read" }, { 1, "read" > }, { 2, "write" }), REC->len, REC->gpa, REC->val > this is not json fromat and its not supper frendly to parse. > > #cat /sys/devices/pci0000:00/0000:00:02.0/uevent > DRIVER=vfio-pci > PCI_CLASS=30000 > PCI_ID=8086:591D > PCI_SUBSYS_ID=8086:2212 > PCI_SLOT_NAME=0000:00:02.0 > MODALIAS=pci:v00008086d0000591Dsv00008086sd00002212bc03sc00i00 > this is ini format or conf formant this is pretty simple to parse whichi would be fine. that said you could also have a version or capablitiy directory with a file for each key and a singel value. i would prefer to only have to do one read personally the list the files in directory and then read tehm all ot build the datastucture myself but that is doable though the simple ini format use d for uevent seams the best of 3 options provided above. > > > > Your idea of having both a "self" object and an array of "compatible" > > objects is perhaps something we can build on, but we must not assume > > PCI devices at the root level of the object. Providing both the > > mdev-type and the driver is a bit redundant, since the former includes > > the latter. We can't have vendor specific versioning schemes though, > > ie. gvt-version. We need to agree on a common scheme and decide which > > fields the version is relative to, ex. just the mdev type? > > what about making all comparing fields vendor specific? > userspace like openstack only needs to parse and compare if target > device is within source compatible list without understanding the meaning > of each field. that kind of defeats the reason for having them be be parsable. the reason openstack want to be able to understand the capablitys is so we can staticaly declare the capablit of devices ahead of time on so our schduler can select host based on that. is the keys and data are opaquce to userspace becaue they are just random vendor sepecific blobs we cant do that.

> > I had also proposed fields that provide information to create a > > compatible type, for example to create a type_x2 device from a type_x1 > > mdev type, they need to know to apply an aggregation attribute. If we > > need to explicitly list every aggregation value and the resulting type, > > I think we run aground of what aggregation was trying to avoid anyway, > > so we might need to pick a language that defines variable substitution > > or some kind of tagging. For example if we could define ${aggr} as an > > integer within a specified range, then we might be able to define a type > > relative to that value (type_x${aggr}) which requires an aggregation > > attribute using the same value. I dunno, just spit balling. Thanks, > > what about a migration_compatible attribute under device node like > below? rather then listing comaptiable devices it would be better if you could declaritivly list the feature supported and we could compare those along with a simple semver version string. > > #cat /sys/bus/pci/devices/0000\:00\:02.0/UUID1/migration_compatible

> SELF: > device_type=pci

> device_id=8086591d

> mdev_type=i915-GVTg_V5_2

> aggregator=1 > pv_mode="none+ppgtt+context"

> interface_version=3

> device_id=8086591d

> aggregator={val1}/2

> pv_mode={val2:string:"none+ppgtt","none+context","none+ppgtt+context"}

> > interface_version={val3:int:2,3}

> device_id=8086591d

> aggregator={val1}/2

if you presented this information the only way i could see to use it would be to extract the mdev_type name and interface_vertion and build a database table as follows source_mdev_type | source_version | target_mdev_type | target_version i915-GVTg_V5_2 | 3 | 915-GVTg_V5_{val1:int:1,2,4,8} | {val3:int:2,3} i915-GVTg_V5_2 | 3 | 915-GVTg_V5_{val1:int:1,2,4,8} | 1 this would either reuiqre use to use a post placment sechudler filter to itrospec this data base or thansform the target_mdev_type and target_version colum data into CUSTOM_* traits we apply to our placment resouce providers and we would have to prefrom multiple reuqest for each posible compatiable alternitive. if the vm has muplite mdevs this is combinatorially problmenatic as it is 1 query for each device * the number of possible compatible devices for that device. in other word if this is just opaque data we cant ever represent it efficently in our placment service and have to fall back to an explisive post placment schdluer filter base on the db table approch. this also ignore the fact that at present the mdev_type cannot change druing a migration so the compatiable devicve with a different mdev type would not be considerd accpetable choice in openstack. they way you select a host with a specific vgpu mdev type today is to apply a custome trait which is CUSTOM_<medev_type_goes_here> to the vGPU resouce provider and then in the flavor you request 1 allcoaton of vGPU and require the CUSTOM_<medev_type_goes_here> trait. so going form i915-GVTg_V5_2 to i915-GVTg_V5_{val1:int:1,2,4,8} would not currently be compatiable with that workflow.

> SELF: > device_type=pci

> device_id=8086591d

> device_id=8086591d

> aggregator={val1}/2

On Wed, 29 Jul 2020 12:28:46 +0100 Sean Mooney <smooney(a)redhat.com&gt; wrote: > On Wed, 2020-07-29 at 16:05 +0800, Yan Zhao wrote: > > On Mon, Jul 27, 2020 at 04:23:21PM -0600, Alex Williamson wrote: > > > On Mon, 27 Jul 2020 15:24:40 +0800 > > > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > > > > > > > As you indicate, the vendor driver is responsible for checking version > > > > > > information embedded within the migration stream. Therefore a > > > > > > migration should fail early if the devices are incompatible. Is it > > > > > > > > > > but as I know, currently in VFIO migration protocol, we have no way to > > > > > get vendor specific compatibility checking string in migration setup stage > > > > > (i.e. .save_setup stage) before the device is set to _SAVING state. > > > > > In this way, for devices who does not save device data in precopy stage, > > > > > the migration compatibility checking is as late as in stop-and-copy > > > > > stage, which is too late. > > > > > do you think we need to add the getting/checking of vendor specific > > > > > compatibility string early in save_setup stage? > > > > > > > > > > > > > hi Alex, > > > > after an offline discussion with Kevin, I realized that it may not be a > > > > problem if migration compatibility check in vendor driver occurs late in > > > > stop-and-copy phase for some devices, because if we report device > > > > compatibility attributes clearly in an interface, the chances for > > > > libvirt/openstack to make a wrong decision is little. > > > > > > I think it would be wise for a vendor driver to implement a pre-copy > > > phase, even if only to send version information and verify it at the > > > target. Deciding you have no device state to send during pre-copy does > > > not mean your vendor driver needs to opt-out of the pre-copy phase > > > entirely. Please also note that pre-copy is at the user's discretion, > > > we've defined that we can enter stop-and-copy at any point, including > > > without a pre-copy phase, so I would recommend that vendor drivers > > > validate compatibility at the start of both the pre-copy and the > > > stop-and-copy phases. > > > > > > > ok. got it! > > > > > > so, do you think we are now arriving at an agreement that we'll give up > > > > the read-and-test scheme and start to defining one interface (perhaps in > > > > json format), from which libvirt/openstack is able to parse and find out > > > > compatibility list of a source mdev/physical device? > > > > > > Based on the feedback we've received, the previously proposed interface > > > is not viable. I think there's agreement that the user needs to be > > > able to parse and interpret the version information. Using json seems > > > viable, but I don't know if it's the best option. Is there any > > > precedent of markup strings returned via sysfs we could follow? > > > > I found some examples of using formatted string under /sys, mostly under > > tracing. maybe we can do a similar implementation. > > > > #cat /sys/kernel/debug/tracing/events/kvm/kvm_mmio/format > > > > name: kvm_mmio > > ID: 32 > > format: > > field:unsigned short common_type; offset:0; size:2; signed:0; > > field:unsigned char common_flags; offset:2; size:1; signed:0; > > field:unsigned char common_preempt_count; offset:3; size:1; signed:0; > > field:int common_pid; offset:4; size:4; signed:1; > > > > field:u32 type; offset:8; size:4; signed:0; > > field:u32 len; offset:12; size:4; signed:0; > > field:u64 gpa; offset:16; size:8; signed:0; > > field:u64 val; offset:24; size:8; signed:0; > > > > print fmt: "mmio %s len %u gpa 0x%llx val 0x%llx", __print_symbolic(REC->type, { 0, "unsatisfied-read" }, { 1, "read" > > }, { 2, "write" }), REC->len, REC->gpa, REC->val > > > this is not json fromat and its not supper frendly to parse. > > > > #cat /sys/devices/pci0000:00/0000:00:02.0/uevent > > DRIVER=vfio-pci > > PCI_CLASS=30000 > > PCI_ID=8086:591D > > PCI_SUBSYS_ID=8086:2212 > > PCI_SLOT_NAME=0000:00:02.0 > > MODALIAS=pci:v00008086d0000591Dsv00008086sd00002212bc03sc00i00 > > > this is ini format or conf formant > this is pretty simple to parse whichi would be fine. > that said you could also have a version or capablitiy directory with a file > for each key and a singel value. > > i would prefer to only have to do one read personally the list the files in > directory and then read tehm all ot build the datastucture myself but that is > doable though the simple ini format use d for uevent seams the best of 3 options > provided above. > > > > > > Your idea of having both a "self" object and an array of "compatible" > > > objects is perhaps something we can build on, but we must not assume > > > PCI devices at the root level of the object. Providing both the > > > mdev-type and the driver is a bit redundant, since the former includes > > > the latter. We can't have vendor specific versioning schemes though, > > > ie. gvt-version. We need to agree on a common scheme and decide which > > > fields the version is relative to, ex. just the mdev type? > > > > what about making all comparing fields vendor specific? > > userspace like openstack only needs to parse and compare if target > > device is within source compatible list without understanding the meaning > > of each field. > that kind of defeats the reason for having them be be parsable. > the reason openstack want to be able to understand the capablitys is so > we can staticaly declare the capablit of devices ahead of time on so our schduler > can select host based on that. is the keys and data are opaquce to userspace > becaue they are just random vendor sepecific blobs we cant do that. Agreed, I'm not sure I'm willing to rule out that there could be vendor specific direct match fields, as I included in my example earlier in the thread, but entirely vendor specific defeats much of the purpose here. > > > I had also proposed fields that provide information to create a > > > compatible type, for example to create a type_x2 device from a type_x1 > > > mdev type, they need to know to apply an aggregation attribute. If we > > > need to explicitly list every aggregation value and the resulting type, > > > I think we run aground of what aggregation was trying to avoid anyway, > > > so we might need to pick a language that defines variable substitution > > > or some kind of tagging. For example if we could define ${aggr} as an > > > integer within a specified range, then we might be able to define a type > > > relative to that value (type_x${aggr}) which requires an aggregation > > > attribute using the same value. I dunno, just spit balling. Thanks, > > > > what about a migration_compatible attribute under device node like > > below? > rather then listing comaptiable devices it would be better if you could declaritivly > list the feature supported and we could compare those along with a simple semver version string. > > > > #cat /sys/bus/pci/devices/0000\:00\:02.0/UUID1/migration_compatible Note that we're defining compatibility relative to a vfio migration interface, so we should include that in the name, we don't know what other migration interfaces might exist.

> > SELF: > > device_type=pci Why not the device_api here, ie. vfio-pci. The device doesn't provide a pci interface directly, it's wrapped in a vfio API.

> > device_id=8086591d Is device_id interpreted relative to device_type? How does this relate to mdev_type? If we have an mdev_type, doesn't that fully defined the software API?

> > mdev_type=i915-GVTg_V5_2 And how are non-mdev devices represented?

> > aggregator=1 > > pv_mode="none+ppgtt+context" These are meaningless vendor specific matches afaict.

> > interface_version=3 Not much granularity here, I prefer Sean's previous <major>.<minor>[.bugfix] scheme.

> > COMPATIBLE: > > device_type=pci > > device_id=8086591d > > mdev_type=i915-GVTg_V5_{val1:int:1,2,4,8} > this mixed notation will be hard to parse so i would avoid that. Some background, Intel has been proposing aggregation as a solution to how we scale mdev devices when hardware exposes large numbers of assignable objects that can be composed in essentially arbitrary ways. So for instance, if we have a workqueue (wq), we might have an mdev type for 1wq, 2wq, 3wq,... Nwq. It's not really practical to expose a discrete mdev type for each of those, so they want to define a base type which is composable to other types via this aggregation. This is what this substitution and tagging is attempting to accomplish. So imagine this set of values for cases where it's not practical to unroll the values for N discrete types. > > aggregator={val1}/2 So the {val1} above would be substituted here, though an aggregation factor of 1/2 is a head scratcher... > > pv_mode={val2:string:"none+ppgtt","none+context","none+ppgtt+context"} I'm lost on this one though. I think maybe it's indicating that it's compatible with any of these, so do we need to list it? Couldn't this be handled by Sean's version proposal where the minor version represents feature compatibility?

> > > > interface_version={val3:int:2,3} What does this turn into in a few years, 2,7,12,23,75,96,...

> > COMPATIBLE: > > device_type=pci > > device_id=8086591d > > mdev_type=i915-GVTg_V5_{val1:int:1,2,4,8} > > aggregator={val1}/2 > > pv_mode="" #"" meaning empty, could be absent in a compatible device > > interface_version=1 Why can't this be represented within the previous compatible description?

> > > interface_version=3 > > Not much granularity here, I prefer Sean's previous > <major>.<minor>[.bugfix] scheme. > yes, <major>.<minor>[.bugfix] scheme may be better, but I'm not sure if it works for a complicated scenario. e.g for pv_mode, (1) initially, pv_mode is not supported, so it's pv_mode=none, it's 0.0.0, (2) then, pv_mode=ppgtt is supported, pv_mode="none+ppgtt", it's 0.1.0, indicating pv_mode=none can migrate to pv_mode="none+ppgtt", but not vice versa. (3) later, pv_mode=context is also supported, pv_mode="none+ppgtt+context", so it's 0.2.0. But if later, pv_mode=ppgtt is removed. pv_mode="none+context", how to name its version?

"none+ppgtt" (0.1.0) is not compatible to "none+context", but "none+ppgtt+context" (0.2.0) is compatible to "none+context". Maintain such scheme is painful to vendor driver.

> yes, include a device_api field is better. > for mdev, "device_type=vfio-mdev", is it right? No, vfio-mdev is not a device API, it's the driver that attaches to the mdev bus device to expose it through vfio. The device_api exposes the actual interface of the vfio device, it's also vfio-pci for typical mdev devices found on x86, but may be vfio-ccw, vfio-ap, etc... See VFIO_DEVICE_API_PCI_STRING and friends.

> > > > device_id=8086591d > > > > Is device_id interpreted relative to device_type? How does this > > relate to mdev_type? If we have an mdev_type, doesn't that fully > > defined the software API? > > > it's parent pci id for mdev actually. If we need to specify the parent PCI ID then something is fundamentally wrong with the mdev_type. The mdev_type should define a unique, software compatible interface, regardless of the parent device IDs. If a i915-GVTg_V5_2 means different things based on the parent device IDs, then then different mdev_types should be reported for those parent devices.

> > > > mdev_type=i915-GVTg_V5_2 > > > > And how are non-mdev devices represented? > > > non-mdev can opt to not include this field, or as you said below, a > vendor signature. > > > > > aggregator=1 > > > > pv_mode="none+ppgtt+context" > > > > These are meaningless vendor specific matches afaict. > > > yes, pv_mode and aggregator are vendor specific fields. > but they are important to decide whether two devices are compatible. > pv_mode means whether a vGPU supports guest paravirtualized api. > "none+ppgtt+context" means guest can not use pv, or use ppgtt mode pv or > use context mode pv. > > > > > interface_version=3 > > > > Not much granularity here, I prefer Sean's previous > > <major>.<minor>[.bugfix] scheme. > > > yes, <major>.<minor>[.bugfix] scheme may be better, but I'm not sure if > it works for a complicated scenario. > e.g for pv_mode, > (1) initially, pv_mode is not supported, so it's pv_mode=none, it's 0.0.0, > (2) then, pv_mode=ppgtt is supported, pv_mode="none+ppgtt", it's 0.1.0, > indicating pv_mode=none can migrate to pv_mode="none+ppgtt", but not vice versa. > (3) later, pv_mode=context is also supported, > pv_mode="none+ppgtt+context", so it's 0.2.0. > > But if later, pv_mode=ppgtt is removed. pv_mode="none+context", how to > name its version? "none+ppgtt" (0.1.0) is not compatible to > "none+context", but "none+ppgtt+context" (0.2.0) is compatible to > "none+context". If pv_mode=ppgtt is removed, then the compatible versions would be 0.0.0 or 1.0.0, ie. the major version would be incremented due to feature removal. > Maintain such scheme is painful to vendor driver. Migration compatibility is painful, there's no way around that. I think the version scheme is an attempt to push some of that low level burden on the vendor driver, otherwise the management tools need to work on an ever growing matrix of vendor specific features which is going to become unwieldy and is largely meaningless outside of the vendor driver. Instead, the vendor driver can make strategic decisions about where to continue to maintain a support burden and make explicit decisions to maintain or break compatibility. The version scheme is a simplification and abstraction of vendor driver features in order to create a small, logical compatibility matrix. Compromises necessarily need to be made for that to occur.

> > > > COMPATIBLE: > > > > device_type=pci > > > > device_id=8086591d > > > > mdev_type=i915-GVTg_V5_{val1:int:1,2,4,8} > > > this mixed notation will be hard to parse so i would avoid that. > > > > Some background, Intel has been proposing aggregation as a solution to > > how we scale mdev devices when hardware exposes large numbers of > > assignable objects that can be composed in essentially arbitrary ways. > > So for instance, if we have a workqueue (wq), we might have an mdev > > type for 1wq, 2wq, 3wq,... Nwq. It's not really practical to expose a > > discrete mdev type for each of those, so they want to define a base > > type which is composable to other types via this aggregation. This is > > what this substitution and tagging is attempting to accomplish. So > > imagine this set of values for cases where it's not practical to unroll > > the values for N discrete types. > > > > > > aggregator={val1}/2 > > > > So the {val1} above would be substituted here, though an aggregation > > factor of 1/2 is a head scratcher... > > > > > > pv_mode={val2:string:"none+ppgtt","none+context","none+ppgtt+context"} > > > > I'm lost on this one though. I think maybe it's indicating that it's > > compatible with any of these, so do we need to list it? Couldn't this > > be handled by Sean's version proposal where the minor version > > represents feature compatibility? > yes, it's indicating that it's compatible with any of these. > Sean's version proposal may also work, but it would be painful for > vendor driver to maintain the versions when multiple similar features > are involved. This is something vendor drivers need to consider when adding and removing features. > > > > interface_version={val3:int:2,3} > > > > What does this turn into in a few years, 2,7,12,23,75,96,... > > > is a range better? I was really trying to point out that sparseness becomes an issue if the vendor driver is largely disconnected from how their feature addition and deprecation affects migration support. Thanks,

On 2020/8/5 上午12:35, Cornelia Huck wrote: > [sorry about not chiming in earlier] > > On Wed, 29 Jul 2020 16:05:03 +0800 > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > On Mon, Jul 27, 2020 at 04:23:21PM -0600, Alex Williamson wrote: > (...) > > > > Based on the feedback we've received, the previously proposed interface > > > is not viable. I think there's agreement that the user needs to be > > > able to parse and interpret the version information. Using json seems > > > viable, but I don't know if it's the best option. Is there any > > > precedent of markup strings returned via sysfs we could follow? > I don't think encoding complex information in a sysfs file is a viable > approach. Quoting Documentation/filesystems/sysfs.rst: > > "Attributes should be ASCII text files, preferably with only one value > per file. It is noted that it may not be efficient to contain only one > value per file, so it is socially acceptable to express an array of > values of the same type. > Mixing types, expressing multiple lines of data, and doing fancy > formatting of data is heavily frowned upon." > > Even though this is an older file, I think these restrictions still > apply. +1, that's another reason why devlink(netlink) is better.

On Wed, Aug 05, 2020 at 10:22:15AM +0800, Jason Wang wrote: > On 2020/8/5 上午12:35, Cornelia Huck wrote: >> [sorry about not chiming in earlier] >> >> On Wed, 29 Jul 2020 16:05:03 +0800 >> Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: >> >>> On Mon, Jul 27, 2020 at 04:23:21PM -0600, Alex Williamson wrote: >> (...) >> >>>> Based on the feedback we've received, the previously proposed interface >>>> is not viable. I think there's agreement that the user needs to be >>>> able to parse and interpret the version information. Using json seems >>>> viable, but I don't know if it's the best option. Is there any >>>> precedent of markup strings returned via sysfs we could follow? >> I don't think encoding complex information in a sysfs file is a viable >> approach. Quoting Documentation/filesystems/sysfs.rst: >> >> "Attributes should be ASCII text files, preferably with only one value >> per file. It is noted that it may not be efficient to contain only one >> value per file, so it is socially acceptable to express an array of >> values of the same type. >> Mixing types, expressing multiple lines of data, and doing fancy >> formatting of data is heavily frowned upon." >> >> Even though this is an older file, I think these restrictions still >> apply. > > +1, that's another reason why devlink(netlink) is better. > hi Jason, do you have any materials or sample code about devlink, so we can have a good study of it? I found some kernel docs about it but my preliminary study didn't show me the advantage of devlink.

Thanks Yan

Wed, Aug 05, 2020 at 04:41:54AM CEST, jasowang(a)redhat.com wrote: > On 2020/8/5 上午10:16, Yan Zhao wrote: >> On Wed, Aug 05, 2020 at 10:22:15AM +0800, Jason Wang wrote: >>> On 2020/8/5 上午12:35, Cornelia Huck wrote: >>>> [sorry about not chiming in earlier] >>>> >>>> On Wed, 29 Jul 2020 16:05:03 +0800 >>>> Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: >>>> >>>>> On Mon, Jul 27, 2020 at 04:23:21PM -0600, Alex Williamson wrote: >>>> (...) >>>> >>>>>> Based on the feedback we've received, the previously proposed interface >>>>>> is not viable. I think there's agreement that the user needs to be >>>>>> able to parse and interpret the version information. Using json seems >>>>>> viable, but I don't know if it's the best option. Is there any >>>>>> precedent of markup strings returned via sysfs we could follow? >>>> I don't think encoding complex information in a sysfs file is a viable >>>> approach. Quoting Documentation/filesystems/sysfs.rst: >>>> >>>> "Attributes should be ASCII text files, preferably with only one value >>>> per file. It is noted that it may not be efficient to contain only one >>>> value per file, so it is socially acceptable to express an array of >>>> values of the same type. >>>> Mixing types, expressing multiple lines of data, and doing fancy >>>> formatting of data is heavily frowned upon." >>>> >>>> Even though this is an older file, I think these restrictions still >>>> apply. >>> +1, that's another reason why devlink(netlink) is better. >>> >> hi Jason, >> do you have any materials or sample code about devlink, so we can have a good >> study of it? >> I found some kernel docs about it but my preliminary study didn't show me the >> advantage of devlink. > > CC Jiri and Parav for a better answer for this. > > My understanding is that the following advantages are obvious (as I replied > in another thread): > > - existing users (NIC, crypto, SCSI, ib), mature and stable > - much better error reporting (ext_ack other than string or errno) > - namespace aware > - do not couple with kobject Jason, what is your use case?

> Thanks > > >> Thanks >> Yan >>

> > yes, include a device_api field is better. > > for mdev, "device_type=vfio-mdev", is it right? > > No, vfio-mdev is not a device API, it's the driver that attaches to the > mdev bus device to expose it through vfio. The device_api exposes the > actual interface of the vfio device, it's also vfio-pci for typical > mdev devices found on x86, but may be vfio-ccw, vfio-ap, etc... See > VFIO_DEVICE_API_PCI_STRING and friends. > ok. got it. > > > > > device_id=8086591d > > > > > > Is device_id interpreted relative to device_type? How does this > > > relate to mdev_type? If we have an mdev_type, doesn't that fully > > > defined the software API? > > > > > it's parent pci id for mdev actually. > > If we need to specify the parent PCI ID then something is fundamentally > wrong with the mdev_type. The mdev_type should define a unique, > software compatible interface, regardless of the parent device IDs. If > a i915-GVTg_V5_2 means different things based on the parent device IDs, > then then different mdev_types should be reported for those parent > devices. > hmm, then do we allow vendor specific fields? or is it a must that a vendor specific field should have corresponding vendor attribute? another thing is that the definition of mdev_type in GVT only corresponds to vGPU computing ability currently, e.g. i915-GVTg_V5_2, is 1/2 of a gen9 IGD, i915-GVTg_V4_2 is 1/2 of a gen8 IGD. It is too coarse-grained to live migration compatibility.

Do you think we need to update GVT's definition of mdev_type? And is there any guide in mdev_type definition? > > > > > mdev_type=i915-GVTg_V5_2 > > > > > > And how are non-mdev devices represented? > > > > > non-mdev can opt to not include this field, or as you said below, a > > vendor signature. > > > > > > > aggregator=1 > > > > > pv_mode="none+ppgtt+context" > > > > > > These are meaningless vendor specific matches afaict. > > > > > yes, pv_mode and aggregator are vendor specific fields. > > but they are important to decide whether two devices are compatible. > > pv_mode means whether a vGPU supports guest paravirtualized api. > > "none+ppgtt+context" means guest can not use pv, or use ppgtt mode pv or > > use context mode pv. > > > > > > > interface_version=3 > > > > > > Not much granularity here, I prefer Sean's previous > > > <major>.<minor>[.bugfix] scheme. > > > > > yes, <major>.<minor>[.bugfix] scheme may be better, but I'm not sure if > > it works for a complicated scenario. > > e.g for pv_mode, > > (1) initially, pv_mode is not supported, so it's pv_mode=none, it's 0.0.0, > > (2) then, pv_mode=ppgtt is supported, pv_mode="none+ppgtt", it's 0.1.0, > > indicating pv_mode=none can migrate to pv_mode="none+ppgtt", but not vice versa. > > (3) later, pv_mode=context is also supported, > > pv_mode="none+ppgtt+context", so it's 0.2.0. > > > > But if later, pv_mode=ppgtt is removed. pv_mode="none+context", how to > > name its version? "none+ppgtt" (0.1.0) is not compatible to > > "none+context", but "none+ppgtt+context" (0.2.0) is compatible to > > "none+context". > > If pv_mode=ppgtt is removed, then the compatible versions would be > 0.0.0 or 1.0.0, ie. the major version would be incremented due to > feature removal. > > > Maintain such scheme is painful to vendor driver. > > Migration compatibility is painful, there's no way around that. I > think the version scheme is an attempt to push some of that low level > burden on the vendor driver, otherwise the management tools need to > work on an ever growing matrix of vendor specific features which is > going to become unwieldy and is largely meaningless outside of the > vendor driver. Instead, the vendor driver can make strategic decisions > about where to continue to maintain a support burden and make explicit > decisions to maintain or break compatibility. The version scheme is a > simplification and abstraction of vendor driver features in order to > create a small, logical compatibility matrix. Compromises necessarily > need to be made for that to occur. > ok. got it. > > > > > COMPATIBLE: > > > > > device_type=pci > > > > > device_id=8086591d > > > > > mdev_type=i915-GVTg_V5_{val1:int:1,2,4,8} > > > > this mixed notation will be hard to parse so i would avoid that. > > > > > > Some background, Intel has been proposing aggregation as a solution to > > > how we scale mdev devices when hardware exposes large numbers of > > > assignable objects that can be composed in essentially arbitrary ways. > > > So for instance, if we have a workqueue (wq), we might have an mdev > > > type for 1wq, 2wq, 3wq,... Nwq. It's not really practical to expose a > > > discrete mdev type for each of those, so they want to define a base > > > type which is composable to other types via this aggregation. This is > > > what this substitution and tagging is attempting to accomplish. So > > > imagine this set of values for cases where it's not practical to unroll > > > the values for N discrete types. > > > > > > > > aggregator={val1}/2 > > > > > > So the {val1} above would be substituted here, though an aggregation > > > factor of 1/2 is a head scratcher... > > > > > > > > pv_mode={val2:string:"none+ppgtt","none+context","none+ppgtt+context"} > > > > > > I'm lost on this one though. I think maybe it's indicating that it's > > > compatible with any of these, so do we need to list it? Couldn't this > > > be handled by Sean's version proposal where the minor version > > > represents feature compatibility? > > yes, it's indicating that it's compatible with any of these. > > Sean's version proposal may also work, but it would be painful for > > vendor driver to maintain the versions when multiple similar features > > are involved. > > This is something vendor drivers need to consider when adding and > removing features. > > > > > > interface_version={val3:int:2,3} > > > > > > What does this turn into in a few years, 2,7,12,23,75,96,... > > > > > is a range better? > > I was really trying to point out that sparseness becomes an issue if > the vendor driver is largely disconnected from how their feature > addition and deprecation affects migration support. Thanks, > ok. we'll use the x.y.z scheme then. Thanks Yan

Wed, Aug 05, 2020 at 11:33:38AM CEST, yan.y.zhao(a)intel.com wrote: > On Wed, Aug 05, 2020 at 04:02:48PM +0800, Jason Wang wrote: > > > > On 2020/8/5 下午3:56, Jiri Pirko wrote: > > > Wed, Aug 05, 2020 at 04:41:54AM CEST, jasowang(a)redhat.com wrote: > > > > On 2020/8/5 上午10:16, Yan Zhao wrote: > > > > > On Wed, Aug 05, 2020 at 10:22:15AM +0800, Jason Wang wrote: > > > > > > On 2020/8/5 上午12:35, Cornelia Huck wrote: > > > > > > > [sorry about not chiming in earlier] > > > > > > > > > > > > > > On Wed, 29 Jul 2020 16:05:03 +0800 > > > > > > > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > > > > > > > > > > > > > On Mon, Jul 27, 2020 at 04:23:21PM -0600, Alex Williamson wrote: > > > > > > > > > > > > > > (...) > > > > > > > > > > > > > > > > Based on the feedback we've received, the previously proposed interface > > > > > > > > > is not viable. I think there's agreement that the user needs to be > > > > > > > > > able to parse and interpret the version information. Using json seems > > > > > > > > > viable, but I don't know if it's the best option. Is there any > > > > > > > > > precedent of markup strings returned via sysfs we could follow? > > > > > > > > > > > > > > I don't think encoding complex information in a sysfs file is a viable > > > > > > > approach. Quoting Documentation/filesystems/sysfs.rst: > > > > > > > > > > > > > > "Attributes should be ASCII text files, preferably with only one value > > > > > > > per file. It is noted that it may not be efficient to contain only one > > > > > > > value per file, so it is socially acceptable to express an array of > > > > > > > values of the same type. > > > > > > > Mixing types, expressing multiple lines of data, and doing fancy > > > > > > > formatting of data is heavily frowned upon." > > > > > > > > > > > > > > Even though this is an older file, I think these restrictions still > > > > > > > apply. > > > > > > > > > > > > +1, that's another reason why devlink(netlink) is better. > > > > > > > > > > > > > > > > hi Jason, > > > > > do you have any materials or sample code about devlink, so we can have a good > > > > > study of it? > > > > > I found some kernel docs about it but my preliminary study didn't show me the > > > > > advantage of devlink. > > > > > > > > CC Jiri and Parav for a better answer for this. > > > > > > > > My understanding is that the following advantages are obvious (as I replied > > > > in another thread): > > > > > > > > - existing users (NIC, crypto, SCSI, ib), mature and stable > > > > - much better error reporting (ext_ack other than string or errno) > > > > - namespace aware > > > > - do not couple with kobject > > > > > > Jason, what is your use case? > > > > > > I think the use case is to report device compatibility for live migration. > > Yan proposed a simple sysfs based migration version first, but it looks not > > sufficient and something based on JSON is discussed. > > > > Yan, can you help to summarize the discussion so far for Jiri as a > > reference? > > > > yes. > we are currently defining an device live migration compatibility > interface in order to let user space like openstack and libvirt knows > which two devices are live migration compatible. > currently the devices include mdev (a kernel emulated virtual device) > and physical devices (e.g. a VF of a PCI SRIOV device). > > the attributes we want user space to compare including > common attribues: > device_api: vfio-pci, vfio-ccw... > mdev_type: mdev type of mdev or similar signature for physical device > It specifies a device's hardware capability. e.g. > i915-GVTg_V5_4 means it's of 1/4 of a gen9 Intel graphics > device.

> software_version: device driver's version. > in <major>.<minor>[.bugfix] scheme, where there is no > compatibility across major versions, minor versions have > forward compatibility (ex. 1-> 2 is ok, 2 -> 1 is not) and > bugfix version number indicates some degree of internal > improvement that is not visible to the user in terms of > features or compatibility, > > vendor specific attributes: each vendor may define different attributes > device id : device id of a physical devices or mdev's parent pci device. > it could be equal to pci id for pci devices > aggregator: used together with mdev_type. e.g. aggregator=2 together > with i915-GVTg_V5_4 means 2*1/4=1/2 of a gen9 Intel > graphics device. > remote_url: for a local NVMe VF, it may be configured with a remote > url of a remote storage and all data is stored in the > remote side specified by the remote url. > ...

> > Comparing those attributes by user space alone is not an easy job, as it > can't simply assume an equal relationship between source attributes and > target attributes. e.g. > for a source device of mdev_type=i915-GVTg_V5_4,aggregator=2, (1/2 of > gen9), it actually could find a compatible device of > mdev_type=i915-GVTg_V5_8,aggregator=4 (also 1/2 of gen9), > if mdev_type of i915-GVTg_V5_4 is not available in the target machine. > > So, in our current proposal, we want to create two sysfs attributes > under a device sysfs node. > /sys/<path to device>/migration/self > /sys/<path to device>/migration/compatible > > #cat /sys/<path to device>/migration/self > device_type=vfio_pci > mdev_type=i915-GVTg_V5_4 > device_id=8086591d > aggregator=2 > software_version=1.0.0 > > #cat /sys/<path to device>/migration/compatible > device_type=vfio_pci > mdev_type=i915-GVTg_V5_{val1:int:2,4,8} > device_id=8086591d > aggregator={val1}/2 > software_version=1.0.0 > > The /sys/<path to device>/migration/self specifies self attributes of > a device. > The /sys/<path to device>/migration/compatible specifies the list of > compatible devices of a device. as in the example, compatible devices > could have > device_type == vfio_pci && > device_id == 8086591d && > software_version == 1.0.0 && > ( > (mdev_type of i915-GVTg_V5_2 && aggregator==1) || > (mdev_type of i915-GVTg_V5_4 && aggregator==2) || > (mdev_type of i915-GVTg_V5_8 && aggregator=4) > ) > > by comparing whether a target device is in compatible list of source > device, the user space can know whether a two devices are live migration > compatible. > > Additional notes: > 1)software_version in the compatible list may not be necessary as it > already has a major.minor.bugfix scheme. > 2)for vendor attribute like remote_url, it may not be statically > assigned and could be changed with a device interface. > > So, as Cornelia pointed that it's not good to use complex format in > a sysfs attribute, we'd like to know whether there're other good ways to > our use case, e.g. splitting a single attribute to multiple simple sysfs > attributes as what Cornelia suggested or devlink that Jason has strongly > recommended. Hi Yan. Thanks for the explanation, I'm still fuzzy about the details. Anyway, I suggest you to check "devlink dev info" command we have implemented for multiple drivers.

You can try netdevsim to test this. I think that the info you need to expose might be put there. Devlink creates instance per-device. Specific device driver calls into devlink core to create the instance. What device do you have? What driver is it handled by? > > Thanks > Yan > > >

Wed, Aug 05, 2020 at 11:33:38AM CEST, yan.y.zhao(a)intel.com wrote: >On Wed, Aug 05, 2020 at 04:02:48PM +0800, Jason Wang wrote: >> >> On 2020/8/5 下午3:56, Jiri Pirko wrote: >> > Wed, Aug 05, 2020 at 04:41:54AM CEST, jasowang(a)redhat.com wrote: >> > > On 2020/8/5 上午10:16, Yan Zhao wrote: >> > > > On Wed, Aug 05, 2020 at 10:22:15AM +0800, Jason Wang wrote: >> > > > > On 2020/8/5 上午12:35, Cornelia Huck wrote: >> > > > > > [sorry about not chiming in earlier] >> > > > > > >> > > > > > On Wed, 29 Jul 2020 16:05:03 +0800 >> > > > > > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: >> > > > > > >> > > > > > > On Mon, Jul 27, 2020 at 04:23:21PM -0600, Alex Williamson wrote: >> > > > > > (...) >> > > > > > >> > > > > > > > Based on the feedback we've received, the previously proposed interface >> > > > > > > > is not viable. I think there's agreement that the user needs to be >> > > > > > > > able to parse and interpret the version information. Using json seems >> > > > > > > > viable, but I don't know if it's the best option. Is there any >> > > > > > > > precedent of markup strings returned via sysfs we could follow? >> > > > > > I don't think encoding complex information in a sysfs file is a viable >> > > > > > approach. Quoting Documentation/filesystems/sysfs.rst: >> > > > > > >> > > > > > "Attributes should be ASCII text files, preferably with only one value >> > > > > > per file. It is noted that it may not be efficient to contain only one >> > > > > > value per file, so it is socially acceptable to express an array of >> > > > > > values of the same type. >> > > > > > Mixing types, expressing multiple lines of data, and doing fancy >> > > > > > formatting of data is heavily frowned upon." >> > > > > > >> > > > > > Even though this is an older file, I think these restrictions still >> > > > > > apply. >> > > > > +1, that's another reason why devlink(netlink) is better. >> > > > > >> > > > hi Jason, >> > > > do you have any materials or sample code about devlink, so we can have a good >> > > > study of it? >> > > > I found some kernel docs about it but my preliminary study didn't show me the >> > > > advantage of devlink. >> > > >> > > CC Jiri and Parav for a better answer for this. >> > > >> > > My understanding is that the following advantages are obvious (as I replied >> > > in another thread): >> > > >> > > - existing users (NIC, crypto, SCSI, ib), mature and stable >> > > - much better error reporting (ext_ack other than string or errno) >> > > - namespace aware >> > > - do not couple with kobject >> > Jason, what is your use case? >> >> >> I think the use case is to report device compatibility for live migration. >> Yan proposed a simple sysfs based migration version first, but it looks not >> sufficient and something based on JSON is discussed. >> >> Yan, can you help to summarize the discussion so far for Jiri as a >> reference? >> >yes. >we are currently defining an device live migration compatibility >interface in order to let user space like openstack and libvirt knows >which two devices are live migration compatible. >currently the devices include mdev (a kernel emulated virtual device) >and physical devices (e.g. a VF of a PCI SRIOV device). > >the attributes we want user space to compare including >common attribues: > device_api: vfio-pci, vfio-ccw... > mdev_type: mdev type of mdev or similar signature for physical device > It specifies a device's hardware capability. e.g. > i915-GVTg_V5_4 means it's of 1/4 of a gen9 Intel graphics > device. > software_version: device driver's version. > in <major>.<minor>[.bugfix] scheme, where there is no > compatibility across major versions, minor versions have > forward compatibility (ex. 1-> 2 is ok, 2 -> 1 is not) and > bugfix version number indicates some degree of internal > improvement that is not visible to the user in terms of > features or compatibility, > >vendor specific attributes: each vendor may define different attributes > device id : device id of a physical devices or mdev's parent pci device. > it could be equal to pci id for pci devices > aggregator: used together with mdev_type. e.g. aggregator=2 together > with i915-GVTg_V5_4 means 2*1/4=1/2 of a gen9 Intel > graphics device. > remote_url: for a local NVMe VF, it may be configured with a remote > url of a remote storage and all data is stored in the > remote side specified by the remote url. > ... > >Comparing those attributes by user space alone is not an easy job, as it >can't simply assume an equal relationship between source attributes and >target attributes. e.g. >for a source device of mdev_type=i915-GVTg_V5_4,aggregator=2, (1/2 of >gen9), it actually could find a compatible device of >mdev_type=i915-GVTg_V5_8,aggregator=4 (also 1/2 of gen9), >if mdev_type of i915-GVTg_V5_4 is not available in the target machine. > >So, in our current proposal, we want to create two sysfs attributes >under a device sysfs node. >/sys/<path to device>/migration/self >/sys/<path to device>/migration/compatible > >#cat /sys/<path to device>/migration/self >device_type=vfio_pci >mdev_type=i915-GVTg_V5_4 >device_id=8086591d >aggregator=2 >software_version=1.0.0 > >#cat /sys/<path to device>/migration/compatible >device_type=vfio_pci >mdev_type=i915-GVTg_V5_{val1:int:2,4,8} >device_id=8086591d >aggregator={val1}/2 >software_version=1.0.0 > >The /sys/<path to device>/migration/self specifies self attributes of >a device. >The /sys/<path to device>/migration/compatible specifies the list of >compatible devices of a device. as in the example, compatible devices >could have > device_type == vfio_pci && > device_id == 8086591d && > software_version == 1.0.0 && > ( > (mdev_type of i915-GVTg_V5_2 && aggregator==1) || > (mdev_type of i915-GVTg_V5_4 && aggregator==2) || > (mdev_type of i915-GVTg_V5_8 && aggregator=4) > ) > >by comparing whether a target device is in compatible list of source >device, the user space can know whether a two devices are live migration >compatible. > >Additional notes: >1)software_version in the compatible list may not be necessary as it >already has a major.minor.bugfix scheme. >2)for vendor attribute like remote_url, it may not be statically >assigned and could be changed with a device interface. > >So, as Cornelia pointed that it's not good to use complex format in >a sysfs attribute, we'd like to know whether there're other good ways to >our use case, e.g. splitting a single attribute to multiple simple sysfs >attributes as what Cornelia suggested or devlink that Jason has strongly >recommended. Hi Yan.

Thanks for the explanation, I'm still fuzzy about the details. Anyway, I suggest you to check "devlink dev info" command we have implemented for multiple drivers. You can try netdevsim to test this. I think that the info you need to expose might be put there.

Devlink creates instance per-device. Specific device driver calls into devlink core to create the instance. What device do you have? What

driver is it handled by?

On Wed, 05 Aug 2020 12:35:01 +0100 Sean Mooney <smooney(a)redhat.com&gt; wrote: > On Wed, 2020-08-05 at 12:53 +0200, Jiri Pirko wrote: > > Wed, Aug 05, 2020 at 11:33:38AM CEST, yan.y.zhao(a)intel.com wrote: (...) > > > software_version: device driver's version. > > > in <major>.<minor>[.bugfix] scheme, where there is no > > > compatibility across major versions, minor versions have > > > forward compatibility (ex. 1-> 2 is ok, 2 -> 1 is not) and > > > bugfix version number indicates some degree of internal > > > improvement that is not visible to the user in terms of > > > features or compatibility, > > > > > > vendor specific attributes: each vendor may define different attributes > > > device id : device id of a physical devices or mdev's parent pci device. > > > it could be equal to pci id for pci devices > > > aggregator: used together with mdev_type. e.g. aggregator=2 together > > > with i915-GVTg_V5_4 means 2*1/4=1/2 of a gen9 Intel > > > graphics device. > > > remote_url: for a local NVMe VF, it may be configured with a remote > > > url of a remote storage and all data is stored in the > > > remote side specified by the remote url. > > > ... > just a minor not that i find ^ much more simmple to understand then > the current proposal with self and compatiable. > if i have well defiend attibute that i can parse and understand that allow > me to calulate the what is and is not compatible that is likely going to > more useful as you wont have to keep maintianing a list of other compatible > devices every time a new sku is released. > > in anycase thank for actully shareing ^ as it make it simpler to reson about what > you have previously proposed. So, what would be the most helpful format? A 'software_version' field that follows the conventions outlined above, and other (possibly optional) fields that have to match?

On 2020/8/10 下午3:46, Yan Zhao wrote: > > driver is it handled by? > It looks that the devlink is for network device specific, and in > devlink.h, it says > include/uapi/linux/devlink.h - Network physical device Netlink > interface, Actually not, I think there used to have some discussion last year and the conclusion is to remove this comment. It supports IB and probably vDPA in the future.

This doesn't seem to be too much related to networking? Why can't something like this be in sysfs?

there is already a way to change eth/ib via echo 'eth' > /sys/bus/pci/drivers/mlx4_core/0000:02:00.0/mlx4_port1 sounds like this is another way to achieve the same?

> I feel like it's not very appropriate for a GPU driver to use > this interface. Is that right? I think not though most of the users are switch or ethernet devices. It doesn't prevent you from inventing new abstractions.

Note that devlink is based on netlink, netlink has been widely used by various subsystems other than networking.

On Fri, 2020-08-14 at 13:16 +0800, Yan Zhao wrote: > On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: > > > > On 2020/8/10 下午3:46, Yan Zhao wrote: > > > > driver is it handled by? > > > > > > It looks that the devlink is for network device specific, and in > > > devlink.h, it says > > > include/uapi/linux/devlink.h - Network physical device Netlink > > > interface, > > > > > > Actually not, I think there used to have some discussion last year and the > > conclusion is to remove this comment. > > > > It supports IB and probably vDPA in the future. > > > > hmm... sorry, I didn't find the referred discussion. only below discussion > regarding to why to add devlink. > > https://www.mail-archive.com/netdev@vger.kernel.org/msg95801.html > >This doesn't seem to be too much related to networking? Why can't something > >like this be in sysfs? > > It is related to networking quite bit. There has been couple of > iteration of this, including sysfs and configfs implementations. There > has been a consensus reached that this should be done by netlink. I > believe netlink is really the best for this purpose. Sysfs is not a good > idea > > https://www.mail-archive.com/netdev@vger.kernel.org/msg96102.html > >there is already a way to change eth/ib via > >echo 'eth' > /sys/bus/pci/drivers/mlx4_core/0000:02:00.0/mlx4_port1 > > > >sounds like this is another way to achieve the same? > > It is. However the current way is driver-specific, not correct. > For mlx5, we need the same, it cannot be done in this way. Do devlink is > the correct way to go. im not sure i agree with that. standardising a filesystem based api that is used across all vendors is also a valid option. that said if devlink is the right choice form a kerenl perspective by all means use it but i have not heard a convincing argument for why it actually better. with tthat said we have been uing tools like ethtool to manage aspect of nics for decades so its not that strange an idea to use a tool and binary protocoal rather then a text based interface for this but there are advantages to both approches. >

> https://lwn.net/Articles/674867/ > There a is need for some userspace API that would allow to expose things > that are not directly related to any device class like net_device of > ib_device, but rather chip-wide/switch-ASIC-wide stuff. > > Use cases: > 1) get/set of port type (Ethernet/InfiniBand) > 2) monitoring of hardware messages to and from chip > 3) setting up port splitters - split port into multiple ones and squash again, > enables usage of splitter cable > 4) setting up shared buffers - shared among multiple ports within one chip > > > > we actually can also retrieve the same information through sysfs, .e.g > > > - [path to device] > > |--- migration > | |--- self > | | |---device_api > | | |---mdev_type > | | |---software_version > | | |---device_id > | | |---aggregator > | |--- compatible > | | |---device_api > | | |---mdev_type > | | |---software_version > | | |---device_id > | | |---aggregator > > > > > > > > I feel like it's not very appropriate for a GPU driver to use > > > this interface. Is that right? > > > > > > I think not though most of the users are switch or ethernet devices. It > > doesn't prevent you from inventing new abstractions. > > so need to patch devlink core and the userspace devlink tool? > e.g. devlink migration and devlink python libs if openstack was to use it directly. we do have caes where we just frok a process and execaute a comannd in a shell with or without elevated privladge but we really dont like doing that due to the performacne impacat and security implciations so where we can use python bindign over c apis we do. pyroute2 is the only python lib i know off of the top of my head that support devlink so we would need to enhacne it to support this new devlink api. there may be otherss i have not really looked in the past since we dont need to use devlink at all today. > > > Note that devlink is based on netlink, netlink has been widely used by > > various subsystems other than networking. > > the advantage of netlink I see is that it can monitor device status and > notify upper layer that migration database needs to get updated. > But not sure whether openstack would like to use this capability. > As Sean said, it's heavy for openstack. it's heavy for vendor driver > as well :) > > And devlink monitor now listens the notification and dumps the state > changes. If we want to use it, need to let it forward the notification > and dumped info to openstack, right? i dont think we would use direct devlink monitoring in nova even if it was avaiable. we could but we already poll libvirt and the system for other resouce periodicly.

we likely wouldl just add monitoriv via devlink to that periodic task. we certenly would not use it to detect a migration or a need to update a migration database(not sure what that is)

in reality if we can consume this info indirectly via a libvirt api that will be the appcoh we will take at least for the libvirt driver in nova. for cyborg they may take a different appoch. we already use pyroute2 in 2 projects, os-vif and neutron and it does have devlink support so the burden of using devlink is not that high for openstack but its a less frineadly interface for configuration tools like ansiable vs a filesystem based approch. >

On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: > On 2020/8/10 下午3:46, Yan Zhao wrote: >>> driver is it handled by? >> It looks that the devlink is for network device specific, and in >> devlink.h, it says >> include/uapi/linux/devlink.h - Network physical device Netlink >> interface, > > Actually not, I think there used to have some discussion last year and the > conclusion is to remove this comment. > > It supports IB and probably vDPA in the future. > hmm... sorry, I didn't find the referred discussion. only below discussion regarding to why to add devlink. https://www.mail-archive.com/netdev@vger.kernel.org/msg95801.html >This doesn't seem to be too much related to networking? Why can't something >like this be in sysfs? It is related to networking quite bit. There has been couple of iteration of this, including sysfs and configfs implementations. There has been a consensus reached that this should be done by netlink. I believe netlink is really the best for this purpose. Sysfs is not a good idea

https://www.mail-archive.com/netdev@vger.kernel.org/msg96102.html >there is already a way to change eth/ib via >echo 'eth' > /sys/bus/pci/drivers/mlx4_core/0000:02:00.0/mlx4_port1 > >sounds like this is another way to achieve the same? It is. However the current way is driver-specific, not correct. For mlx5, we need the same, it cannot be done in this way. Do devlink is the correct way to go. https://lwn.net/Articles/674867/ There a is need for some userspace API that would allow to expose things that are not directly related to any device class like net_device of ib_device, but rather chip-wide/switch-ASIC-wide stuff. Use cases: 1) get/set of port type (Ethernet/InfiniBand) 2) monitoring of hardware messages to and from chip 3) setting up port splitters - split port into multiple ones and squash again, enables usage of splitter cable 4) setting up shared buffers - shared among multiple ports within one chip we actually can also retrieve the same information through sysfs, .e.g |- [path to device] |--- migration | |--- self | | |---device_api | | |---mdev_type | | |---software_version | | |---device_id | | |---aggregator | |--- compatible | | |---device_api | | |---mdev_type | | |---software_version | | |---device_id | | |---aggregator

>> I feel like it's not very appropriate for a GPU driver to use >> this interface. Is that right? > > I think not though most of the users are switch or ethernet devices. It > doesn't prevent you from inventing new abstractions. so need to patch devlink core and the userspace devlink tool? e.g. devlink migration

> Note that devlink is based on netlink, netlink has been widely used by > various subsystems other than networking. the advantage of netlink I see is that it can monitor device status and notify upper layer that migration database needs to get updated.

But not sure whether openstack would like to use this capability. As Sean said, it's heavy for openstack. it's heavy for vendor driver as well :)

And devlink monitor now listens the notification and dumps the state changes. If we want to use it, need to let it forward the notification and dumped info to openstack, right? Thanks Yan

On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: On 2020/8/14 下午1:16, Yan Zhao wrote: On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: On 2020/8/10 下午3:46, Yan Zhao wrote:

we actually can also retrieve the same information through sysfs, .e.g |- [path to device] |--- migration | |--- self | | |---device_api | | |---mdev_type | | |---software_version | | |---device_id | | |---aggregator | |--- compatible | | |---device_api | | |---mdev_type | | |---software_version | | |---device_id | | |---aggregator Yes but: - You need one file per attribute (one syscall for one attribute) - Attribute is coupled with kobject All of above seems unnecessary. Another point, as we discussed in another thread, it's really hard to make sure the above API work for all types of devices and frameworks. So having a vendor specific API looks much better. From the POV of userspace mgmt apps doing device compat checking / migration, we certainly do NOT want to use different vendor specific APIs. We want to have an API that can be used / controlled in a standard manner across vendors. Yes, but it could be hard. E.g vDPA will chose to use devlink (there's a long debate on sysfs vs devlink). So if we go with sysfs, at least two APIs needs to be supported ...

Yes, but it could be hard. E.g vDPA will chose to use devlink (there's a long debate on sysfs vs devlink). So if we go with sysfs, at least two APIs needs to be supported ...

On Tue, Aug 18, 2020 at 11:06:17AM +0200, Cornelia Huck wrote: > On Tue, 18 Aug 2020 09:55:27 +0100 > Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > > > On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: > > > Another point, as we discussed in another thread, it's really hard to make > > > sure the above API work for all types of devices and frameworks. So having a > > > vendor specific API looks much better. > > > > From the POV of userspace mgmt apps doing device compat checking / migration, > > we certainly do NOT want to use different vendor specific APIs. We want to > > have an API that can be used / controlled in a standard manner across vendors. > > As we certainly will need to have different things to check for > different device types and vendor drivers, would it still be fine to > have differing (say) attributes, as long as they are presented (and can > be discovered) in a standardized way? Yes, the control API and algorithm to deal with the problem needs to have standardization, but the data passed in/out of the APIs can vary. Essentially the key is that vendors should be able to create devices at the kernel, and those devices should "just work" with the existing generic userspace migration / compat checking code, without needing extra vendor specific logic to be added. Note, I'm not saying that the userspace decisions would be perfectly optimal based on generic code. They might be making a simplified decision that while functionally safe, is not the ideal solution. Adding vendor specific code might be able to optimize the userspace decisions, but that should be considered just optimization, not a core must have for any opertion.

Your mail came through as HTML-only so all the quoting and attribution is mangled / lost now :-(

On Tue, Aug 18, 2020 at 05:01:51PM +0800, Jason Wang wrote: > On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: > > On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: > > On 2020/8/14 下午1:16, Yan Zhao wrote: > > On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: > > On 2020/8/10 下午3:46, Yan Zhao wrote: > we actually can also retrieve the same information through sysfs, .e.g > > |- [path to device] > |--- migration > | |--- self > | | |---device_api > | | |---mdev_type > | | |---software_version > | | |---device_id > | | |---aggregator > | |--- compatible > | | |---device_api > | | |---mdev_type > | | |---software_version > | | |---device_id > | | |---aggregator > > > Yes but: > > - You need one file per attribute (one syscall for one attribute) > - Attribute is coupled with kobject > > All of above seems unnecessary. > > Another point, as we discussed in another thread, it's really hard to make > sure the above API work for all types of devices and frameworks. So having a > vendor specific API looks much better. > > From the POV of userspace mgmt apps doing device compat checking / migration, > we certainly do NOT want to use different vendor specific APIs. We want to > have an API that can be used / controlled in a standard manner across vendors. > > Yes, but it could be hard. E.g vDPA will chose to use devlink (there's a > long debate on sysfs vs devlink). So if we go with sysfs, at least two > APIs needs to be supported ... NB, I was not questioning devlink vs sysfs directly. If devlink is related to netlink, I can't say I'm enthusiastic as IMKE sysfs is easier to deal with. I don't know enough about devlink to have much of an opinion though. The key point was that I don't want the userspace APIs we need to deal with to be vendor specific. What I care about is that we have a *standard* userspace API for performing device compatibility checking / state migration, for use by QEMU/libvirt/ OpenStack, such that we can write code without countless vendor specific code paths. If there is vendor specific stuff on the side, that's fine as we can ignore that, but the core functionality for device compat / migration needs to be standardized.

Regards, Daniel

On Tue, 18 Aug 2020 10:16:28 +0100 Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > On Tue, Aug 18, 2020 at 05:01:51PM +0800, Jason Wang wrote: >> On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: >> >> On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: >> >> On 2020/8/14 下午1:16, Yan Zhao wrote: >> >> On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: >> >> On 2020/8/10 下午3:46, Yan Zhao wrote: >> we actually can also retrieve the same information through sysfs, .e.g >> >> |- [path to device] >> |--- migration >> | |--- self >> | | |---device_api >> | | |---mdev_type >> | | |---software_version >> | | |---device_id >> | | |---aggregator >> | |--- compatible >> | | |---device_api >> | | |---mdev_type >> | | |---software_version >> | | |---device_id >> | | |---aggregator >> >> >> Yes but: >> >> - You need one file per attribute (one syscall for one attribute) >> - Attribute is coupled with kobject Is that really that bad? You have the device with an embedded kobject anyway, and you can just put things into an attribute group?

[Also, I think that self/compatible split in the example makes things needlessly complex. Shouldn't semantic versioning and matching already cover nearly everything?

I would expect very few cases that are more complex than that. Maybe the aggregation stuff, but I don't think we need that self/compatible split for that, either.] >> All of above seems unnecessary. >> >> Another point, as we discussed in another thread, it's really hard to make >> sure the above API work for all types of devices and frameworks. So having a >> vendor specific API looks much better. >> >> From the POV of userspace mgmt apps doing device compat checking / migration, >> we certainly do NOT want to use different vendor specific APIs. We want to >> have an API that can be used / controlled in a standard manner across vendors. >> >> Yes, but it could be hard. E.g vDPA will chose to use devlink (there's a >> long debate on sysfs vs devlink). So if we go with sysfs, at least two >> APIs needs to be supported ... > NB, I was not questioning devlink vs sysfs directly. If devlink is related > to netlink, I can't say I'm enthusiastic as IMKE sysfs is easier to deal > with. I don't know enough about devlink to have much of an opinion though. > The key point was that I don't want the userspace APIs we need to deal with > to be vendor specific. From what I've seen of devlink, it seems quite nice; but I understand why sysfs might be easier to deal with (especially as there's likely already a lot of code using it.) I understand that some users would like devlink because it is already widely used for network drivers (and some others), but I don't think the majority of devices used with vfio are network (although certainly a lot of them are.)

> What I care about is that we have a *standard* userspace API for performing > device compatibility checking / state migration, for use by QEMU/libvirt/ > OpenStack, such that we can write code without countless vendor specific > code paths. > > If there is vendor specific stuff on the side, that's fine as we can ignore > that, but the core functionality for device compat / migration needs to be > standardized. To summarize: - choose one of sysfs or devlink - have a common interface, with a standardized way to add vendor-specific attributes ?

From: Jason Wang <jasowang(a)redhat.com&gt; Sent: Wednesday, August 19, 2020 8:16 AM

On 2020/8/18 下午5:32, Parav Pandit wrote: > Hi Jason, > > From: Jason Wang <jasowang(a)redhat.com&gt; > Sent: Tuesday, August 18, 2020 2:32 PM > > > On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: > On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: > On 2020/8/14 下午1:16, Yan Zhao wrote: > On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: > On 2020/8/10 下午3:46, Yan Zhao wrote: > driver is it handled by? > It looks that the devlink is for network device specific, and in > devlink.h, it says include/uapi/linux/devlink.h - Network physical > device Netlink interface, Actually not, I think there used to have > some discussion last year and the conclusion is to remove this > comment. > > [...] > >> Yes, but it could be hard. E.g vDPA will chose to use devlink (there's a long debate on sysfs vs devlink). So if we go with sysfs, at least two APIs needs to be supported ... > We had internal discussion and proposal on this topic. > I wanted Eli Cohen to be back from vacation on Wed 8/19, but since this is active discussion right now, I will share the thoughts anyway. > > Here are the initial round of thoughts and proposal. > > User requirements: > --------------------------- > 1. User might want to create one or more vdpa devices per PCI PF/VF/SF. > 2. User might want to create one or more vdpa devices of type net/blk or other type. > 3. User needs to look and dump at the health of the queues for debug purpose. > 4. During vdpa net device creation time, user may have to provide a MAC address and/or VLAN. > 5. User should be able to set/query some of the attributes for > debug/compatibility check 6. When user wants to create vdpa device, it needs to know which device supports creation. > 7. User should be able to see the queue statistics of doorbells, wqes > etc regardless of class type Note that wqes is probably not something common in all of the vendors.

> > To address above requirements, there is a need of vendor agnostic tool, so that user can create/config/delete vdpa device(s) regardless of the vendor. > > Hence, > We should have a tool that lets user do it. > > Examples: > ------------- > (a) List parent devices which supports creating vdpa devices. > It also shows which class types supported by this parent device. > In below command two parent devices support vdpa device creation. > First is PCI VF whose bdf is 03.00:5. > Second is PCI SF whose name is mlx5_sf.1 > > $ vdpa list pd What did "pd" mean?

> pci/0000:03.00:5 > class_supports > net vdpa > virtbus/mlx5_sf.1 So creating mlx5_sf.1 is the charge of devlink?

> class_supports > net > > (b) Now add a vdpa device and show the device. > $ vdpa dev add pci/0000:03.00:5 type net So if you want to create devices types other than vdpa on pci/0000:03.00:5 it needs some synchronization with devlink?

> $ vdpa dev show > vdpa0@pci/0000:03.00:5 type net state inactive maxqueues 8 curqueues 4 > > (c) vdpa dev show features vdpa0 > iommu platform > version 1 > > (d) dump vdpa statistics > $ vdpa dev stats show vdpa0 > kickdoorbells 10 > wqes 100 > > (e) Now delete a vdpa device previously created. > $ vdpa dev del vdpa0 > > Design overview: > ----------------------- > 1. Above example tool runs over netlink socket interface. > 2. This enables users to return meaningful error strings in addition to code so that user can be more informed. > Often this is missing in ioctl()/configfs/sysfs interfaces. > 3. This tool over netlink enables syscaller tests to be more usable like other subsystems to keep kernel robust > 4. This provides vendor agnostic view of all vdpa capable parent and vdpa devices. > > 5. Each driver which supports vdpa device creation, registers the parent device along with supported classes. > > FAQs: > -------- > 1. Why not using devlink? > Ans: Because as vdpa echo system grows, devlink will fall short of extending vdpa specific params, attributes, stats. This should be fine but it's still not clear to me the difference between a vdpa netlink and a vdpa object in devlink.

> From: Jason Wang <jasowang(a)redhat.com&gt; > Sent: Wednesday, August 19, 2020 8:16 AM > On 2020/8/18 下午5:32, Parav Pandit wrote: >> Hi Jason, >> >> From: Jason Wang <jasowang(a)redhat.com&gt; >> Sent: Tuesday, August 18, 2020 2:32 PM >> >> >> On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: >> On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: >> On 2020/8/14 下午1:16, Yan Zhao wrote: >> On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: >> On 2020/8/10 下午3:46, Yan Zhao wrote: >> driver is it handled by? >> It looks that the devlink is for network device specific, and in >> devlink.h, it says include/uapi/linux/devlink.h - Network physical >> device Netlink interface, Actually not, I think there used to have >> some discussion last year and the conclusion is to remove this >> comment. >> >> [...] >> >>> Yes, but it could be hard. E.g vDPA will chose to use devlink (there's a long > debate on sysfs vs devlink). So if we go with sysfs, at least two APIs needs to be > supported ... >> We had internal discussion and proposal on this topic. >> I wanted Eli Cohen to be back from vacation on Wed 8/19, but since this is > active discussion right now, I will share the thoughts anyway. >> Here are the initial round of thoughts and proposal. >> >> User requirements: >> --------------------------- >> 1. User might want to create one or more vdpa devices per PCI PF/VF/SF. >> 2. User might want to create one or more vdpa devices of type net/blk or > other type. >> 3. User needs to look and dump at the health of the queues for debug purpose. >> 4. During vdpa net device creation time, user may have to provide a MAC > address and/or VLAN. >> 5. User should be able to set/query some of the attributes for >> debug/compatibility check 6. When user wants to create vdpa device, it needs > to know which device supports creation. >> 7. User should be able to see the queue statistics of doorbells, wqes >> etc regardless of class type > > Note that wqes is probably not something common in all of the vendors. Yes. I virtq descriptors stats is better to monitor the virtqueues. > >> To address above requirements, there is a need of vendor agnostic tool, so > that user can create/config/delete vdpa device(s) regardless of the vendor. >> Hence, >> We should have a tool that lets user do it. >> >> Examples: >> ------------- >> (a) List parent devices which supports creating vdpa devices. >> It also shows which class types supported by this parent device. >> In below command two parent devices support vdpa device creation. >> First is PCI VF whose bdf is 03.00:5. >> Second is PCI SF whose name is mlx5_sf.1 >> >> $ vdpa list pd > > What did "pd" mean? > Parent device which support creation of one or more vdpa devices. In a system there can be multiple parent devices which may be support vdpa creation. User should be able to know which devices support it, and when user creates a vdpa device, it tells which parent device to use for creation as done in below vdpa dev add example. >> pci/0000:03.00:5 >> class_supports >> net vdpa >> virtbus/mlx5_sf.1 > > So creating mlx5_sf.1 is the charge of devlink? > Yes. But here vdpa tool is working at the parent device identifier {bus+name} instead of devlink identifier. >> class_supports >> net >> >> (b) Now add a vdpa device and show the device. >> $ vdpa dev add pci/0000:03.00:5 type net > > So if you want to create devices types other than vdpa on > pci/0000:03.00:5 it needs some synchronization with devlink? Please refer to FAQ-1, a new tool is not linked to devlink because vdpa will evolve with time and devlink will fall short. So no, it doesn't need any synchronization with devlink. As long as parent device exist, user can create it. All synchronization will be within drivers/vdpa/vdpa.c This user interface is exposed via new netlink family by doing genl_register_family() with new name "vdpa" in drivers/vdpa/vdpa.c.

> >> $ vdpa dev show >> vdpa0@pci/0000:03.00:5 type net state inactive maxqueues 8 curqueues 4 >> >> (c) vdpa dev show features vdpa0 >> iommu platform >> version 1 >> >> (d) dump vdpa statistics >> $ vdpa dev stats show vdpa0 >> kickdoorbells 10 >> wqes 100 >> >> (e) Now delete a vdpa device previously created. >> $ vdpa dev del vdpa0 >> >> Design overview: >> ----------------------- >> 1. Above example tool runs over netlink socket interface. >> 2. This enables users to return meaningful error strings in addition to code so > that user can be more informed. >> Often this is missing in ioctl()/configfs/sysfs interfaces. >> 3. This tool over netlink enables syscaller tests to be more usable like other > subsystems to keep kernel robust >> 4. This provides vendor agnostic view of all vdpa capable parent and vdpa > devices. >> 5. Each driver which supports vdpa device creation, registers the parent device > along with supported classes. >> FAQs: >> -------- >> 1. Why not using devlink? >> Ans: Because as vdpa echo system grows, devlink will fall short of extending > vdpa specific params, attributes, stats. > > > This should be fine but it's still not clear to me the difference > between a vdpa netlink and a vdpa object in devlink. > The difference is a vdpa specific tool work at the parent device level. It is likely more appropriate to because it can self-contain everything needed to create/delete devices, view/set features, stats. Trying to put that in devlink will fall short as devlink doesn’t have vdpa definitions. Typically when a class/device subsystem grows, its own tool is wiser like iproute2/ip, iproute2/tc, iproute2/rdma.

hi All, could we decide that sysfs is the interface that every VFIO vendor driver needs to provide in order to support vfio live migration, otherwise the userspace management tool would not list the device into the compatible list? if that's true, let's move to the standardizing of the sysfs interface. (1) content common part: (must) - software_version: (in major.minor.bugfix scheme)

- device_api: vfio-pci or vfio-ccw ... - type: mdev type for mdev device or a signature for physical device which is a counterpart for mdev type. device api specific part: (must) - pci id: pci id of mdev parent device or pci id of physical pci device (device_api is vfio-pci)API here.

- subchannel_type (device_api is vfio-ccw) vendor driver specific part: (optional) - aggregator - chpid_type - remote_url

NOTE: vendors are free to add attributes in this part with a restriction that this attribute is able to be configured with the same name in sysfs too. e.g.

for aggregator, there must be a sysfs attribute in device node /sys/devices/pci0000:00/0000:00:02.0/882cc4da-dede-11e7-9180-078a62063ab1/intel_vgpu/aggregator, so that the userspace tool is able to configure the target device according to source device's aggregator attribute. (2) where and structure proposal 1: |- [path to device] |--- migration | |--- self | | |-software_version | | |-device_api | | |-type | | |-[pci_id or subchannel_type] | | |-<aggregator or chpid_type> | |--- compatible | | |-software_version | | |-device_api | | |-type | | |-[pci_id or subchannel_type] | | |-<aggregator or chpid_type> multiple compatible is allowed. attributes should be ASCII text files, preferably with only one value per file. proposal 2: use bin_attribute. |- [path to device] |--- migration | |--- self | |--- compatible so we can continue use multiline format. e.g. cat compatible software_version=0.1.0 device_api=vfio_pci type=i915-GVTg_V5_{val1:int:1,2,4,8} pci_id=80865963 aggregator={val1}/2

Thanks Yan

On Wed, Aug 19, 2020 at 02:57:34PM +0800, Jason Wang wrote: > On 2020/8/19 上午11:30, Yan Zhao wrote: >> hi All, >> could we decide that sysfs is the interface that every VFIO vendor driver >> needs to provide in order to support vfio live migration, otherwise the >> userspace management tool would not list the device into the compatible >> list? >> >> if that's true, let's move to the standardizing of the sysfs interface. >> (1) content >> common part: (must) >> - software_version: (in major.minor.bugfix scheme) > > This can not work for devices whose features can be negotiated/advertised > independently. (E.g virtio devices) > sorry, I don't understand here, why virtio devices need to use vfio interface?

I think this thread is discussing about vfio related devices. >> - device_api: vfio-pci or vfio-ccw ... >> - type: mdev type for mdev device or >> a signature for physical device which is a counterpart for >> mdev type. >> >> device api specific part: (must) >> - pci id: pci id of mdev parent device or pci id of physical pci >> device (device_api is vfio-pci)API here. > > So this assumes a PCI device which is probably not true. > for device_api of vfio-pci, why it's not true? for vfio-ccw, it's subchannel_type.

>> - subchannel_type (device_api is vfio-ccw) >> vendor driver specific part: (optional) >> - aggregator >> - chpid_type >> - remote_url > > For "remote_url", just wonder if it's better to integrate or reuse the > existing NVME management interface instead of duplicating it here. Otherwise > it could be a burden for mgmt to learn. E.g vendor A may use "remote_url" > but vendor B may use a different attribute. > it's vendor driver specific. vendor specific attributes are inevitable, and that's why we are discussing here of a way to standardizing of it.

our goal is that mgmt can use it without understanding the meaning of vendor specific attributes.

>> NOTE: vendors are free to add attributes in this part with a >> restriction that this attribute is able to be configured with the same >> name in sysfs too. e.g. > > Sysfs works well for common attributes belongs to a class, but I'm not sure > it can work well for device/vendor specific attributes. Does this mean mgmt > need to iterate all the attributes in both src and dst? > no. just attributes under migration directory. >> for aggregator, there must be a sysfs attribute in device node >> /sys/devices/pci0000:00/0000:00:02.0/882cc4da-dede-11e7-9180-078a62063ab1/intel_vgpu/aggregator, >> so that the userspace tool is able to configure the target device >> according to source device's aggregator attribute. >> >> >> (2) where and structure >> proposal 1: >> |- [path to device] >> |--- migration >> | |--- self >> | | |-software_version >> | | |-device_api >> | | |-type >> | | |-[pci_id or subchannel_type] >> | | |-<aggregator or chpid_type> >> | |--- compatible >> | | |-software_version >> | | |-device_api >> | | |-type >> | | |-[pci_id or subchannel_type] >> | | |-<aggregator or chpid_type> >> multiple compatible is allowed. >> attributes should be ASCII text files, preferably with only one value >> per file. >> >> >> proposal 2: use bin_attribute. >> |- [path to device] >> |--- migration >> | |--- self >> | |--- compatible >> >> so we can continue use multiline format. e.g. >> cat compatible >> software_version=0.1.0 >> device_api=vfio_pci >> type=i915-GVTg_V5_{val1:int:1,2,4,8} >> pci_id=80865963 >> aggregator={val1}/2 > > So basically two questions: > > - how hard to standardize sysfs API for dealing with compatibility check (to > make it work for most types of devices) sorry, I just know we are in the process of standardizing of it :)

> - how hard for the mgmt to learn with a vendor specific attributes (vs > existing management API) what is existing management API?

Thanks

On Wed, Aug 19, 2020 at 03:39:50PM +0800, Jason Wang wrote: > On 2020/8/19 下午2:59, Yan Zhao wrote: >> On Wed, Aug 19, 2020 at 02:57:34PM +0800, Jason Wang wrote: >>> On 2020/8/19 上午11:30, Yan Zhao wrote: >>>> hi All, >>>> could we decide that sysfs is the interface that every VFIO vendor driver >>>> needs to provide in order to support vfio live migration, otherwise the >>>> userspace management tool would not list the device into the compatible >>>> list? >>>> >>>> if that's true, let's move to the standardizing of the sysfs interface. >>>> (1) content >>>> common part: (must) >>>> - software_version: (in major.minor.bugfix scheme) >>> This can not work for devices whose features can be negotiated/advertised >>> independently. (E.g virtio devices) >>> >> sorry, I don't understand here, why virtio devices need to use vfio interface? > > I don't see any reason that virtio devices can't be used by VFIO. Do you? > > Actually, virtio devices have been used by VFIO for many years: > > - passthrough a hardware virtio devices to userspace(VM) drivers > - using virtio PMD inside guest > So, what's different for it vs passing through a physical hardware via VFIO?

even though the features are negotiated dynamically, could you explain why it would cause software_version not work?

>> I think this thread is discussing about vfio related devices. >> >>>> - device_api: vfio-pci or vfio-ccw ... >>>> - type: mdev type for mdev device or >>>> a signature for physical device which is a counterpart for >>>> mdev type. >>>> >>>> device api specific part: (must) >>>> - pci id: pci id of mdev parent device or pci id of physical pci >>>> device (device_api is vfio-pci)API here. >>> So this assumes a PCI device which is probably not true. >>> >> for device_api of vfio-pci, why it's not true? >> >> for vfio-ccw, it's subchannel_type. > > Ok but having two different attributes for the same file is not good idea. > How mgmt know there will be a 3rd type? that's why some attributes need to be common. e.g. device_api: it's common because mgmt need to know it's a pci device or a ccw device. and the api type is already defined vfio.h. (The field is agreed by and actually suggested by Alex in previous mail) type: mdev_type for mdev. if mgmt does not understand it, it would not be able to create one compatible mdev device. software_version: mgmt can compare the major and minor if it understands this fields.

> >>>> - subchannel_type (device_api is vfio-ccw) >>>> vendor driver specific part: (optional) >>>> - aggregator >>>> - chpid_type >>>> - remote_url >>> For "remote_url", just wonder if it's better to integrate or reuse the >>> existing NVME management interface instead of duplicating it here. Otherwise >>> it could be a burden for mgmt to learn. E.g vendor A may use "remote_url" >>> but vendor B may use a different attribute. >>> >> it's vendor driver specific. >> vendor specific attributes are inevitable, and that's why we are >> discussing here of a way to standardizing of it. > > Well, then you will end up with a very long list to discuss. E.g for > networking devices, you will have "mac", "v(x)lan" and a lot of other. > > Note that "remote_url" is not vendor specific but NVME (class/subsystem) > specific. > yes, it's just NVMe specific. I added it as an example to show what is vendor specific. if one attribute is vendor specific across all vendors, then it's not vendor specific, it's already common attribute, right?

> The point is that if vendor/class specific part is unavoidable, why not > making all of the attributes vendor specific? > some parts need to be common, as I listed above.

>> our goal is that mgmt can use it without understanding the meaning of vendor >> specific attributes. > > I'm not sure this is the correct design of uAPI. Is there something similar > in the existing uAPIs? > > And it might be hard to work for virtio devices. > > >>>> NOTE: vendors are free to add attributes in this part with a >>>> restriction that this attribute is able to be configured with the same >>>> name in sysfs too. e.g. >>> Sysfs works well for common attributes belongs to a class, but I'm not sure >>> it can work well for device/vendor specific attributes. Does this mean mgmt >>> need to iterate all the attributes in both src and dst? >>> >> no. just attributes under migration directory. >> >>>> for aggregator, there must be a sysfs attribute in device node >>>> /sys/devices/pci0000:00/0000:00:02.0/882cc4da-dede-11e7-9180-078a62063ab1/intel_vgpu/aggregator, >>>> so that the userspace tool is able to configure the target device >>>> according to source device's aggregator attribute. >>>> >>>> >>>> (2) where and structure >>>> proposal 1: >>>> |- [path to device] >>>> |--- migration >>>> | |--- self >>>> | | |-software_version >>>> | | |-device_api >>>> | | |-type >>>> | | |-[pci_id or subchannel_type] >>>> | | |-<aggregator or chpid_type> >>>> | |--- compatible >>>> | | |-software_version >>>> | | |-device_api >>>> | | |-type >>>> | | |-[pci_id or subchannel_type] >>>> | | |-<aggregator or chpid_type> >>>> multiple compatible is allowed. >>>> attributes should be ASCII text files, preferably with only one value >>>> per file. >>>> >>>> >>>> proposal 2: use bin_attribute. >>>> |- [path to device] >>>> |--- migration >>>> | |--- self >>>> | |--- compatible >>>> >>>> so we can continue use multiline format. e.g. >>>> cat compatible >>>> software_version=0.1.0 >>>> device_api=vfio_pci >>>> type=i915-GVTg_V5_{val1:int:1,2,4,8} >>>> pci_id=80865963 >>>> aggregator={val1}/2 >>> So basically two questions: >>> >>> - how hard to standardize sysfs API for dealing with compatibility check (to >>> make it work for most types of devices) >> sorry, I just know we are in the process of standardizing of it :) > > It's not easy. As I said, the current design can't work for virtio devices > and it's not hard to find other examples. I remember some Intel devices have > bitmask based capability registers. > some Intel devices have bitmask based capability registers. so what?

we have defined pci_id to identify the devices. even two different devices have equal PCI IDs, we still allow them to add vendor specific fields. e.g. for QAT, they can add alg_set to identify hardware supported algorithms.

>>> - how hard for the mgmt to learn with a vendor specific attributes (vs >>> existing management API) >> what is existing management API? > > It depends on the type of devices. E.g for NVME, we've already had one > (/sys/kernel/config/nvme)? > if the device is binding to vfio or vfio-mdev, I believe this interface is not there.

Thanks Yan

On Tue, Aug 18, 2020 at 09:39:24AM +0000, Parav Pandit wrote: > Hi Cornelia, > > > From: Cornelia Huck <cohuck(a)redhat.com&gt; > > Sent: Tuesday, August 18, 2020 3:07 PM > > To: Daniel P. Berrangé <berrange(a)redhat.com&gt; > > Cc: Jason Wang <jasowang(a)redhat.com>; Yan Zhao > > <yan.y.zhao(a)intel.com>; kvm(a)vger.kernel.org; libvir-list(a)redhat.com; > > qemu-devel(a)nongnu.org; Kirti Wankhede <kwankhede(a)nvidia.com>; > > eauger(a)redhat.com; xin-ran.wang(a)intel.com; corbet(a)lwn.net; openstack- > > discuss(a)lists.openstack.org; shaohe.feng(a)intel.com; kevin.tian(a)intel.com; > > Parav Pandit <parav(a)mellanox.com>; jian-feng.ding(a)intel.com; > > dgilbert(a)redhat.com; zhenyuw(a)linux.intel.com; hejie.xu(a)intel.com; > > bao.yumeng(a)zte.com.cn; Alex Williamson <alex.williamson(a)redhat.com>; > > eskultet(a)redhat.com; smooney(a)redhat.com; intel-gvt- > > dev(a)lists.freedesktop.org; Jiri Pirko <jiri(a)mellanox.com>; > > dinechin(a)redhat.com; devel(a)ovirt.org > > Subject: Re: device compatibility interface for live migration with assigned > > devices > > > > On Tue, 18 Aug 2020 10:16:28 +0100 > > Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > > > > > On Tue, Aug 18, 2020 at 05:01:51PM +0800, Jason Wang wrote: > > > > On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: > > > > > > > > On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: > > > > > > > > On 2020/8/14 下午1:16, Yan Zhao wrote: > > > > > > > > On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: > > > > > > > > On 2020/8/10 下午3:46, Yan Zhao wrote: > > > > > > > we actually can also retrieve the same information through sysfs, > > > > .e.g > > > > > > > > |- [path to device] > > > > |--- migration > > > > | |--- self > > > > | | |---device_api > > > > | | |---mdev_type > > > > | | |---software_version > > > > | | |---device_id > > > > | | |---aggregator > > > > | |--- compatible > > > > | | |---device_api > > > > | | |---mdev_type > > > > | | |---software_version > > > > | | |---device_id > > > > | | |---aggregator > > > > > > > > > > > > Yes but: > > > > > > > > - You need one file per attribute (one syscall for one attribute) > > > > - Attribute is coupled with kobject > > > > Is that really that bad? You have the device with an embedded kobject > > anyway, and you can just put things into an attribute group? > > > > [Also, I think that self/compatible split in the example makes things > > needlessly complex. Shouldn't semantic versioning and matching already > > cover nearly everything? I would expect very few cases that are more > > complex than that. Maybe the aggregation stuff, but I don't think we need > > that self/compatible split for that, either.] > > > > > > > > > > All of above seems unnecessary. > > > > > > > > Another point, as we discussed in another thread, it's really hard > > > > to make sure the above API work for all types of devices and > > > > frameworks. So having a vendor specific API looks much better. > > > > > > > > From the POV of userspace mgmt apps doing device compat checking / > > > > migration, we certainly do NOT want to use different vendor > > > > specific APIs. We want to have an API that can be used / controlled in a > > standard manner across vendors. > > > > > > > > Yes, but it could be hard. E.g vDPA will chose to use devlink (there's a > > > > long debate on sysfs vs devlink). So if we go with sysfs, at least two > > > > APIs needs to be supported ... > > > > > > NB, I was not questioning devlink vs sysfs directly. If devlink is > > > related to netlink, I can't say I'm enthusiastic as IMKE sysfs is > > > easier to deal with. I don't know enough about devlink to have much of an > > opinion though. > > > The key point was that I don't want the userspace APIs we need to deal > > > with to be vendor specific. > > > > From what I've seen of devlink, it seems quite nice; but I understand why > > sysfs might be easier to deal with (especially as there's likely already a lot of > > code using it.) > > > > I understand that some users would like devlink because it is already widely > > used for network drivers (and some others), but I don't think the majority of > > devices used with vfio are network (although certainly a lot of them are.) > > > > > > > > What I care about is that we have a *standard* userspace API for > > > performing device compatibility checking / state migration, for use by > > > QEMU/libvirt/ OpenStack, such that we can write code without countless > > > vendor specific code paths. > > > > > > If there is vendor specific stuff on the side, that's fine as we can > > > ignore that, but the core functionality for device compat / migration > > > needs to be standardized. > > > > To summarize: > > - choose one of sysfs or devlink > > - have a common interface, with a standardized way to add > > vendor-specific attributes > > ? > > Please refer to my previous email which has more example and details. hi Parav, the example is based on a new vdpa tool running over netlink, not based on devlink, right? For vfio migration compatibility, we have to deal with both mdev and physical pci devices, I don't think it's a good idea to write a new tool for it, given we are able to retrieve the same info from sysfs and there's already an mdevctl from Alex (https://github.com/mdevctl/mdevctl). hi All, could we decide that sysfs is the interface that every VFIO vendor driver needs to provide in order to support vfio live migration, otherwise the userspace management tool would not list the device into the compatible list? if that's true, let's move to the standardizing of the sysfs interface. (1) content common part: (must) - software_version: (in major.minor.bugfix scheme) - device_api: vfio-pci or vfio-ccw ... - type: mdev type for mdev device or a signature for physical device which is a counterpart for mdev type. device api specific part: (must) - pci id: pci id of mdev parent device or pci id of physical pci device (device_api is vfio-pci)

- subchannel_type (device_api is vfio-ccw) vendor driver specific part: (optional) - aggregator - chpid_type - remote_url NOTE: vendors are free to add attributes in this part with a restriction that this attribute is able to be configured with the same name in sysfs too. e.g. for aggregator, there must be a sysfs attribute in device node /sys/devices/pci0000:00/0000:00:02.0/882cc4da-dede-11e7-9180-078a62063ab1/intel_vgpu/aggregator, so that the userspace tool is able to configure the target device according to source device's aggregator attribute. (2) where and structure proposal 1: |- [path to device] |--- migration | |--- self | | |-software_version | | |-device_api | | |-type | | |-[pci_id or subchannel_type] | | |-<aggregator or chpid_type> | |--- compatible | | |-software_version | | |-device_api | | |-type | | |-[pci_id or subchannel_type] | | |-<aggregator or chpid_type> multiple compatible is allowed. attributes should be ASCII text files, preferably with only one value per file. proposal 2: use bin_attribute. |- [path to device] |--- migration | |--- self | |--- compatible so we can continue use multiline format. e.g. cat compatible software_version=0.1.0 device_api=vfio_pci type=i915-GVTg_V5_{val1:int:1,2,4,8} pci_id=80865963 aggregator={val1}/2 Thanks Yan

On Tue, 18 Aug 2020 10:16:28 +0100 Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > On Tue, Aug 18, 2020 at 05:01:51PM +0800, Jason Wang wrote: > > On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: > > > > On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: > > > > On 2020/8/14 下午1:16, Yan Zhao wrote: > > > > On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: > > > > On 2020/8/10 下午3:46, Yan Zhao wrote: > > > we actually can also retrieve the same information through sysfs, .e.g > > > > |- [path to device] > > |--- migration > > | |--- self > > | | |---device_api > > | | |---mdev_type > > | | |---software_version > > | | |---device_id > > | | |---aggregator > > | |--- compatible > > | | |---device_api > > | | |---mdev_type > > | | |---software_version > > | | |---device_id > > | | |---aggregator > > > > > > Yes but: > > > > - You need one file per attribute (one syscall for one attribute) > > - Attribute is coupled with kobject Is that really that bad? You have the device with an embedded kobject anyway, and you can just put things into an attribute group? [Also, I think that self/compatible split in the example makes things needlessly complex. Shouldn't semantic versioning and matching already cover nearly everything? I would expect very few cases that are more complex than that. Maybe the aggregation stuff, but I don't think we need that self/compatible split for that, either.]

On Thu, 20 Aug 2020 08:18:10 +0800 Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > On Wed, Aug 19, 2020 at 11:50:21AM -0600, Alex Williamson wrote: > <...> > > > > > > What I care about is that we have a *standard* userspace API for > > > > > > performing device compatibility checking / state migration, for use by > > > > > > QEMU/libvirt/ OpenStack, such that we can write code without countless > > > > > > vendor specific code paths. > > > > > > > > > > > > If there is vendor specific stuff on the side, that's fine as we can > > > > > > ignore that, but the core functionality for device compat / migration > > > > > > needs to be standardized. > > > > > > > > > > To summarize: > > > > > - choose one of sysfs or devlink > > > > > - have a common interface, with a standardized way to add > > > > > vendor-specific attributes > > > > > ? > > > > > > > > Please refer to my previous email which has more example and details. > > > hi Parav, > > > the example is based on a new vdpa tool running over netlink, not based > > > on devlink, right? > > > For vfio migration compatibility, we have to deal with both mdev and physical > > > pci devices, I don't think it's a good idea to write a new tool for it, given > > > we are able to retrieve the same info from sysfs and there's already an > > > mdevctl from Alex (https://github.com/mdevctl/mdevctl). > > > > > > hi All, > > > could we decide that sysfs is the interface that every VFIO vendor driver > > > needs to provide in order to support vfio live migration, otherwise the > > > userspace management tool would not list the device into the compatible > > > list? > > > > > > if that's true, let's move to the standardizing of the sysfs interface. > > > (1) content > > > common part: (must) > > > - software_version: (in major.minor.bugfix scheme) > > > - device_api: vfio-pci or vfio-ccw ... > > > - type: mdev type for mdev device or > > > a signature for physical device which is a counterpart for > > > mdev type. > > > > > > device api specific part: (must) > > > - pci id: pci id of mdev parent device or pci id of physical pci > > > device (device_api is vfio-pci) > > > > As noted previously, the parent PCI ID should not matter for an mdev > > device, if a vendor has a dependency on matching the parent device PCI > > ID, that's a vendor specific restriction. An mdev device can also > > expose a vfio-pci device API without the parent device being PCI. For > > a physical PCI device, shouldn't the PCI ID be encompassed in the > > signature? Thanks, > > > you are right. I need to put the PCI ID as a vendor specific field. > I didn't do that because I wanted all fields in vendor specific to be > configurable by management tools, so they can configure the target device > according to the value of a vendor specific field even they don't know > the meaning of the field. > But maybe they can just ignore the field when they can't find a matching > writable field to configure the target. If fields can be ignored, what's the point of reporting them? Seems it's no longer a requirement. Thanks,

On Thu, 20 Aug 2020 08:39:22 +0800 Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > On Tue, Aug 18, 2020 at 11:36:52AM +0200, Cornelia Huck wrote: > > On Tue, 18 Aug 2020 10:16:28 +0100 > > Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > > > > > On Tue, Aug 18, 2020 at 05:01:51PM +0800, Jason Wang wrote: > > > > On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: > > > > > > > > On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: > > > > > > > > On 2020/8/14 下午1:16, Yan Zhao wrote: > > > > > > > > On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: > > > > > > > > On 2020/8/10 下午3:46, Yan Zhao wrote: > > > > > > > we actually can also retrieve the same information through sysfs, .e.g > > > > > > > > |- [path to device] > > > > |--- migration > > > > | |--- self > > > > | | |---device_api > > > > | | |---mdev_type > > > > | | |---software_version > > > > | | |---device_id > > > > | | |---aggregator > > > > | |--- compatible > > > > | | |---device_api > > > > | | |---mdev_type > > > > | | |---software_version > > > > | | |---device_id > > > > | | |---aggregator > > > > > > > > > > > > Yes but: > > > > > > > > - You need one file per attribute (one syscall for one attribute) > > > > - Attribute is coupled with kobject > > > > Is that really that bad? You have the device with an embedded kobject > > anyway, and you can just put things into an attribute group? > > > > [Also, I think that self/compatible split in the example makes things > > needlessly complex. Shouldn't semantic versioning and matching already > > cover nearly everything? I would expect very few cases that are more > > complex than that. Maybe the aggregation stuff, but I don't think we > > need that self/compatible split for that, either.] > Hi Cornelia, > > The reason I want to declare compatible list of attributes is that > sometimes it's not a simple 1:1 matching of source attributes and target attributes > as I demonstrated below, > source mdev of (mdev_type i915-GVTg_V5_2 + aggregator 1) is compatible to > target mdev of (mdev_type i915-GVTg_V5_4 + aggregator 2), > (mdev_type i915-GVTg_V5_8 + aggregator 4) > > and aggragator may be just one of such examples that 1:1 matching does not > fit. If you're suggesting that we need a new 'compatible' set for every aggregation, haven't we lost the purpose of aggregation? For example, rather than having N mdev types to represent all the possible aggregation values, we have a single mdev type with N compatible migration entries, one for each possible aggregation value. BTW, how do we have multiple compatible directories? compatible0001, compatible0002? Thanks,

On Thu, 2020-08-20 at 08:39 +0800, Yan Zhao wrote: > On Tue, Aug 18, 2020 at 11:36:52AM +0200, Cornelia Huck wrote: > > On Tue, 18 Aug 2020 10:16:28 +0100 > > Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > > > > > On Tue, Aug 18, 2020 at 05:01:51PM +0800, Jason Wang wrote: > > > > On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: > > > > > > > > On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: > > > > > > > > On 2020/8/14 下午1:16, Yan Zhao wrote: > > > > > > > > On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: > > > > > > > > On 2020/8/10 下午3:46, Yan Zhao wrote: > > > > we actually can also retrieve the same information through sysfs, .e.g > > > > > > > > |- [path to device] > > > > |--- migration > > > > | |--- self > > > > | | |---device_api > > > > | | |---mdev_type > > > > | | |---software_version > > > > | | |---device_id > > > > | | |---aggregator > > > > | |--- compatible > > > > | | |---device_api > > > > | | |---mdev_type > > > > | | |---software_version > > > > | | |---device_id > > > > | | |---aggregator > > > > > > > > > > > > Yes but: > > > > > > > > - You need one file per attribute (one syscall for one attribute) > > > > - Attribute is coupled with kobject > > > > Is that really that bad? You have the device with an embedded kobject > > anyway, and you can just put things into an attribute group? > > > > [Also, I think that self/compatible split in the example makes things > > needlessly complex. Shouldn't semantic versioning and matching already > > cover nearly everything? I would expect very few cases that are more > > complex than that. Maybe the aggregation stuff, but I don't think we > > need that self/compatible split for that, either.] > > Hi Cornelia, > > The reason I want to declare compatible list of attributes is that > sometimes it's not a simple 1:1 matching of source attributes and target attributes > as I demonstrated below, > source mdev of (mdev_type i915-GVTg_V5_2 + aggregator 1) is compatible to > target mdev of (mdev_type i915-GVTg_V5_4 + aggregator 2), > (mdev_type i915-GVTg_V5_8 + aggregator 4) the way you are doing the nameing is till really confusing by the way if this has not already been merged in the kernel can you chagne the mdev so that mdev_type i915-GVTg_V5_2 is 2 of mdev_type i915-GVTg_V5_1 instead of half the device currently you need to deived the aggratod by the number at the end of the mdev type to figure out how much of the phsicial device is being used with is a very unfridly api convention the way aggrator are being proposed in general is not really someting i like but i thin this at least is something that should be able to correct. with the complexity in the mdev type name + aggrator i suspect that this will never be support in openstack nova directly requireing integration via cyborg unless we can pre partion the device in to mdevs staicaly and just ignore this. this is way to vendor sepecif to integrate into something like openstack in nova unless we can guarentee taht how aggreator work will be portable across vendors genericly. > > and aggragator may be just one of such examples that 1:1 matching does not > fit. for openstack nova i dont see us support anything beyond the 1:1 case where the mdev type does not change.

On Thu, 2020-08-20 at 12:01 +0800, Yan Zhao wrote: > On Thu, Aug 20, 2020 at 02:29:07AM +0100, Sean Mooney wrote: > > On Thu, 2020-08-20 at 08:39 +0800, Yan Zhao wrote: > > > On Tue, Aug 18, 2020 at 11:36:52AM +0200, Cornelia Huck wrote: > > > > On Tue, 18 Aug 2020 10:16:28 +0100 > > > > Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > > > > > > > > > On Tue, Aug 18, 2020 at 05:01:51PM +0800, Jason Wang wrote: > > > > > > On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: > > > > > > > > > > > > On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: > > > > > > > > > > > > On 2020/8/14 下午1:16, Yan Zhao wrote: > > > > > > > > > > > > On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: > > > > > > > > > > > > On 2020/8/10 下午3:46, Yan Zhao wrote: > > > > > > we actually can also retrieve the same information through sysfs, .e.g > > > > > > > > > > > > |- [path to device] > > > > > > |--- migration > > > > > > | |--- self > > > > > > | | |---device_api > > > > > > | | |---mdev_type > > > > > > | | |---software_version > > > > > > | | |---device_id > > > > > > | | |---aggregator > > > > > > | |--- compatible > > > > > > | | |---device_api > > > > > > | | |---mdev_type > > > > > > | | |---software_version > > > > > > | | |---device_id > > > > > > | | |---aggregator > > > > > > > > > > > > > > > > > > Yes but: > > > > > > > > > > > > - You need one file per attribute (one syscall for one attribute) > > > > > > - Attribute is coupled with kobject > > > > > > > > Is that really that bad? You have the device with an embedded kobject > > > > anyway, and you can just put things into an attribute group? > > > > > > > > [Also, I think that self/compatible split in the example makes things > > > > needlessly complex. Shouldn't semantic versioning and matching already > > > > cover nearly everything? I would expect very few cases that are more > > > > complex than that. Maybe the aggregation stuff, but I don't think we > > > > need that self/compatible split for that, either.] > > > > > > Hi Cornelia, > > > > > > The reason I want to declare compatible list of attributes is that > > > sometimes it's not a simple 1:1 matching of source attributes and target attributes > > > as I demonstrated below, > > > source mdev of (mdev_type i915-GVTg_V5_2 + aggregator 1) is compatible to > > > target mdev of (mdev_type i915-GVTg_V5_4 + aggregator 2), > > > (mdev_type i915-GVTg_V5_8 + aggregator 4) > > > > the way you are doing the nameing is till really confusing by the way > > if this has not already been merged in the kernel can you chagne the mdev > > so that mdev_type i915-GVTg_V5_2 is 2 of mdev_type i915-GVTg_V5_1 instead of half the device > > > > currently you need to deived the aggratod by the number at the end of the mdev type to figure out > > how much of the phsicial device is being used with is a very unfridly api convention > > > > the way aggrator are being proposed in general is not really someting i like but i thin this at least > > is something that should be able to correct. > > > > with the complexity in the mdev type name + aggrator i suspect that this will never be support > > in openstack nova directly requireing integration via cyborg unless we can pre partion the > > device in to mdevs staicaly and just ignore this. > > > > this is way to vendor sepecif to integrate into something like openstack in nova unless we can guarentee > > taht how aggreator work will be portable across vendors genericly. > > > > > > > > and aggragator may be just one of such examples that 1:1 matching does not > > > fit. > > > > for openstack nova i dont see us support anything beyond the 1:1 case where the mdev type does not change. > > > > hi Sean, > I understand it's hard for openstack. but 1:N is always meaningful. > e.g. > if source device 1 has cap A, it is compatible to > device 2: cap A, > device 3: cap A+B, > device 4: cap A+B+C > .... > to allow openstack to detect it correctly, in compatible list of > device 2, we would say compatible cap is A; > device 3, compatible cap is A or A+B; > device 4, compatible cap is A or A+B, or A+B+C; > > then if openstack finds device A's self cap A is contained in compatible > cap of device 2/3/4, it can migrate device 1 to device 2,3,4. > > conversely, device 1's compatible cap is only A, > so it is able to migrate device 2 to device 1, and it is not able to > migrate device 3/4 to device 1. yes we build the palcement servce aroudn the idea of capablites as traits on resocue providres. which is why i originally asked if we coudl model compatibality with feature flags we can seaislyt model deivce as aupport A, A+B or A+B+C and then select hosts and evice based on that but the list of compatable deivce you are propsoeing hide this feature infomation which whould be what we are matching on. give me a lset of feature you want and list ting the feature avaiable on each device allow highre level ocestation to easily match the request to a host that can fulllfile it btu thave a set of other compatihble device does not help with that so if a simple list a capabliteis can be advertiese d and if we know tha two dievce with the same capablity are intercahangebale that is workabout i suspect that will not be the case however and it would onely work within a familay of mdevs that are closely related. which i think agian is an argument for not changeing the mdev type and at least intially only look at migatreion where the mdev type doee not change initally.

On Thu, Aug 20, 2020 at 06:16:28AM +0100, Sean Mooney wrote: > On Thu, 2020-08-20 at 12:01 +0800, Yan Zhao wrote: > > On Thu, Aug 20, 2020 at 02:29:07AM +0100, Sean Mooney wrote: > > > On Thu, 2020-08-20 at 08:39 +0800, Yan Zhao wrote: > > > > On Tue, Aug 18, 2020 at 11:36:52AM +0200, Cornelia Huck wrote: > > > > > On Tue, 18 Aug 2020 10:16:28 +0100 > > > > > Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > > > > > > > > > > > On Tue, Aug 18, 2020 at 05:01:51PM +0800, Jason Wang wrote: > > > > > > > On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: > > > > > > > > > > > > > > On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: > > > > > > > > > > > > > > On 2020/8/14 下午1:16, Yan Zhao wrote: > > > > > > > > > > > > > > On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: > > > > > > > > > > > > > > On 2020/8/10 下午3:46, Yan Zhao wrote: > > > > > > > we actually can also retrieve the same information through sysfs, .e.g > > > > > > > > > > > > > > |- [path to device] > > > > > > > |--- migration > > > > > > > | |--- self > > > > > > > | | |---device_api > > > > > > > | | |---mdev_type > > > > > > > | | |---software_version > > > > > > > | | |---device_id > > > > > > > | | |---aggregator > > > > > > > | |--- compatible > > > > > > > | | |---device_api > > > > > > > | | |---mdev_type > > > > > > > | | |---software_version > > > > > > > | | |---device_id > > > > > > > | | |---aggregator > > > > > > > > > > > > > > > > > > > > > Yes but: > > > > > > > > > > > > > > - You need one file per attribute (one syscall for one attribute) > > > > > > > - Attribute is coupled with kobject > > > > > > > > > > Is that really that bad? You have the device with an embedded kobject > > > > > anyway, and you can just put things into an attribute group? > > > > > > > > > > [Also, I think that self/compatible split in the example makes things > > > > > needlessly complex. Shouldn't semantic versioning and matching already > > > > > cover nearly everything? I would expect very few cases that are more > > > > > complex than that. Maybe the aggregation stuff, but I don't think we > > > > > need that self/compatible split for that, either.] > > > > > > > > Hi Cornelia, > > > > > > > > The reason I want to declare compatible list of attributes is that > > > > sometimes it's not a simple 1:1 matching of source attributes and target attributes > > > > as I demonstrated below, > > > > source mdev of (mdev_type i915-GVTg_V5_2 + aggregator 1) is compatible to > > > > target mdev of (mdev_type i915-GVTg_V5_4 + aggregator 2), > > > > (mdev_type i915-GVTg_V5_8 + aggregator 4) > > > > > > the way you are doing the nameing is till really confusing by the way > > > if this has not already been merged in the kernel can you chagne the mdev > > > so that mdev_type i915-GVTg_V5_2 is 2 of mdev_type i915-GVTg_V5_1 instead of half the device > > > > > > currently you need to deived the aggratod by the number at the end of the mdev type to figure out > > > how much of the phsicial device is being used with is a very unfridly api convention > > > > > > the way aggrator are being proposed in general is not really someting i like but i thin this at least > > > is something that should be able to correct. > > > > > > with the complexity in the mdev type name + aggrator i suspect that this will never be support > > > in openstack nova directly requireing integration via cyborg unless we can pre partion the > > > device in to mdevs staicaly and just ignore this. > > > > > > this is way to vendor sepecif to integrate into something like openstack in nova unless we can guarentee > > > taht how aggreator work will be portable across vendors genericly. > > > > > > > > > > > and aggragator may be just one of such examples that 1:1 matching does not > > > > fit. > > > > > > for openstack nova i dont see us support anything beyond the 1:1 case where the mdev type does not change. > > > > > > > hi Sean, > > I understand it's hard for openstack. but 1:N is always meaningful. > > e.g. > > if source device 1 has cap A, it is compatible to > > device 2: cap A, > > device 3: cap A+B, > > device 4: cap A+B+C > > .... > > to allow openstack to detect it correctly, in compatible list of > > device 2, we would say compatible cap is A; > > device 3, compatible cap is A or A+B; > > device 4, compatible cap is A or A+B, or A+B+C; > > > > then if openstack finds device A's self cap A is contained in compatible > > cap of device 2/3/4, it can migrate device 1 to device 2,3,4. > > > > conversely, device 1's compatible cap is only A, > > so it is able to migrate device 2 to device 1, and it is not able to > > migrate device 3/4 to device 1. > > yes we build the palcement servce aroudn the idea of capablites as traits on resocue providres. > which is why i originally asked if we coudl model compatibality with feature flags > > we can seaislyt model deivce as aupport A, A+B or A+B+C > and then select hosts and evice based on that but > > the list of compatable deivce you are propsoeing hide this feature infomation which whould be what we are matching > on. > > give me a lset of feature you want and list ting the feature avaiable on each device allow highre level ocestation > to > easily match the request to a host that can fulllfile it btu thave a set of other compatihble device does not help > with > that > > so if a simple list a capabliteis can be advertiese d and if we know tha two dievce with the same capablity are > intercahangebale that is workabout i suspect that will not be the case however and it would onely work within a > familay > of mdevs that are closely related. which i think agian is an argument for not changeing the mdev type and at least > intially only look at migatreion where the mdev type doee not change initally. > sorry Sean, I don't understand your words completely. Please allow me to write it down in my words, and please confirm if my understanding is right. 1. you mean you agree on that each field is regarded as a trait, and openstack can compare by itself if source trait is a subset of target trait, right? e.g. source device field1=A1 field2=A2+B2 field3=A3 target device field1=A1+B1 field2=A2+B2 filed3=A3 then openstack sees that field1/2/3 in source is a subset of field1/2/3 in target, so it's migratable to target?

2. mdev_type + aggregator make it hard to achieve the above elegant solution, so it's best to avoid the combined comparing of mdev_type + aggregator. do I understand it correctly?

3. you don't like self list and compatible list, because it is hard for openstack to compare different traits? e.g. if we have self list and compatible list, then as below, openstack needs to compare if self field1/2/3 is a subset of compatible field 1/2/3.

source device: self field1=A1 self field2=A2+B2 self field3=A3 compatible field1=A1 compatible field2=A2;B2;A2+B2; compatible field3=A3 target device: self field1=A1+B1 self field2=A2+B2 self field3=A3 compatible field1=A1;B1;A1+B1; compatible field2=A2;B2;A2+B2; compatible field3=A3 Thanks Yan > > > > > > > i woudl really prefer if there was just one mdev type that repsented the minimal allcatable unit and the > > > aggragaotr where used to create compostions of that. i.e instad of i915-GVTg_V5_2 beign half the device, > > > have 1 mdev type i915-GVTg and if the device support 8 of them then we can aggrate 4 of i915-GVTg > > > > > > if you want to have muplie mdev type to model the different amoutn of the resouce e.g. i915-GVTg_small i915- > > > GVTg_large > > > that is totlaly fine too or even i915-GVTg_4 indcating it sis 4 of i915-GVTg > > > > > > failing that i would just expose an mdev type per composable resouce and allow us to compose them a the user > > > level > > > with > > > some other construct mudeling a attament to the device. e.g. create composed mdev or somethig that is an > > > aggreateion > > > of > > > multiple sub resouces each of which is an mdev. so kind of like how bond port work. we would create an mdev for > > > each > > > of > > > the sub resouces and then create a bond or aggrated mdev by reference the other mdevs by uuid then attach only > > > the > > > aggreated mdev to the instance. > > > > > > the current aggrator syntax and sematic however make me rather uncofrotable when i think about orchestating vms > > > on > > > top > > > of it even to boot them let alone migrate them. > > > > > > > > So, we explicitly list out self/compatible attributes, and management > > > > tools only need to check if self attributes is contained compatible > > > > attributes. > > > > > > > > or do you mean only compatible list is enough, and the management tools > > > > need to find out self list by themselves? > > > > But I think provide a self list is easier for management tools. > > > > > > > > Thanks > > > > Yan > > > > > > > >

On 2020/8/20 下午8:27, Cornelia Huck wrote: > On Wed, 19 Aug 2020 17:28:38 +0800 > Jason Wang <jasowang(a)redhat.com&gt; wrote: > >> On 2020/8/19 下午4:13, Yan Zhao wrote: >>> On Wed, Aug 19, 2020 at 03:39:50PM +0800, Jason Wang wrote: >>>> On 2020/8/19 下午2:59, Yan Zhao wrote: >>>>> On Wed, Aug 19, 2020 at 02:57:34PM +0800, Jason Wang wrote: >>>>>> On 2020/8/19 上午11:30, Yan Zhao wrote: >>>>>>> hi All, >>>>>>> could we decide that sysfs is the interface that every VFIO vendor driver >>>>>>> needs to provide in order to support vfio live migration, otherwise the >>>>>>> userspace management tool would not list the device into the compatible >>>>>>> list? >>>>>>> >>>>>>> if that's true, let's move to the standardizing of the sysfs interface. >>>>>>> (1) content >>>>>>> common part: (must) >>>>>>> - software_version: (in major.minor.bugfix scheme) >>>>>> This can not work for devices whose features can be negotiated/advertised >>>>>> independently. (E.g virtio devices) > I thought the 'software_version' was supposed to describe kind of a > 'protocol version' for the data we transmit? I.e., you add a new field, > you bump the version number. Ok, but since we mandate backward compatibility of uABI, is this really worth to have a version for sysfs? (Searching on sysfs shows no examples like this)

>>>>>>> - device_api: vfio-pci or vfio-ccw ... >>>>>>> - type: mdev type for mdev device or >>>>>>> a signature for physical device which is a counterpart for >>>>>>> mdev type. >>>>>>> >>>>>>> device api specific part: (must) >>>>>>> - pci id: pci id of mdev parent device or pci id of physical pci >>>>>>> device (device_api is vfio-pci)API here. >>>>>> So this assumes a PCI device which is probably not true. >>>>>> >>>>> for device_api of vfio-pci, why it's not true? >>>>> >>>>> for vfio-ccw, it's subchannel_type. >>>> Ok but having two different attributes for the same file is not good idea. >>>> How mgmt know there will be a 3rd type? >>> that's why some attributes need to be common. e.g. >>> device_api: it's common because mgmt need to know it's a pci device or a >>> ccw device. and the api type is already defined vfio.h. >>> (The field is agreed by and actually suggested by Alex in previous mail) >>> type: mdev_type for mdev. if mgmt does not understand it, it would not >>> be able to create one compatible mdev device. >>> software_version: mgmt can compare the major and minor if it understands >>> this fields. >> >> I think it would be helpful if you can describe how mgmt is expected to >> work step by step with the proposed sysfs API. This can help people to >> understand. > My proposal would be: > - check that device_api matches > - check possible device_api specific attributes > - check that type matches [I don't think the combination of mdev types > and another attribute to determine compatibility is a good idea; Any reason for this? Actually if we only use mdev type to detect the compatibility, it would be much more easier. Otherwise, we are actually re-inventing mdev types. E.g can we have the same mdev types with different device_api and other attributes?

> actually, the current proposal confuses me every time I look at it] > - check that software_version is compatible, assuming semantic > versioning > - check possible type-specific attributes I'm not sure if this is too complicated. And I suspect there will be vendor specific attributes: - for compatibility check: I think we should either modeling everything via mdev type or making it totally vendor specific. Having something in the middle will bring a lot of burden

- for provisioning: it's still not clear. As shown in this proposal, for NVME we may need to set remote_url, but unless there will be a subclass (NVME) in the mdev (which I guess not), we can't prevent vendor from using another attribute name, in this case, tricks like attributes iteration in some sub directory won't work. So even if we had some common API for compatibility check, the provisioning API is still vendor specific ...

> do you think the bin_attribute I proposed yesterday good? > Then we can have a single compatible with a variable in the mdev_type and > aggregator. > > mdev_type=i915-GVTg_V5_{val1:int:2,4,8} > aggregator={val1}/2 I'm not really a fan of binary attributes other than in cases where we have some kind of binary format to begin with. IIUC, we basically have: - different partitioning (expressed in the mdev_type) - different number of partitions (expressed via the aggregator) - devices being compatible if the partitioning:aggregator ratio is the same (The multiple mdev_type variants seem to come from avoiding extra creation parameters, IIRC?) Would it be enough to export base_type=i915-GVTg_V5 aggregation_ratio=<integer> to express the various combinations that are compatible without the need for multiple sets of attributes?

previously, we want to regard the two mdevs created with dsa-1dwq x 30 and dsa-2dwq x 15 as compatible, because the two mdevs consist equal resources. But, as it's a burden to upper layer, we agree that if this condition happens, we still treat the two as incompatible. To fix it, either the driver should expose dsa-1dwq only, or the target dsa-2dwq needs to be destroyed and reallocated via dsa-1dwq x 30.

On Wed, 26 Aug 2020 14:41:17 +0800 Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > previously, we want to regard the two mdevs created with dsa-1dwq x 30 and > dsa-2dwq x 15 as compatible, because the two mdevs consist equal resources. > > But, as it's a burden to upper layer, we agree that if this condition > happens, we still treat the two as incompatible. > > To fix it, either the driver should expose dsa-1dwq only, or the target > dsa-2dwq needs to be destroyed and reallocated via dsa-1dwq x 30. AFAIU, these are mdev types, aren't they? So, basically, any management software needs to take care to use the matching mdev type on the target system for device creation?

On Fri, 2020-08-28 at 15:47 +0200, Cornelia Huck wrote: > On Wed, 26 Aug 2020 14:41:17 +0800 > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > previously, we want to regard the two mdevs created with dsa-1dwq x 30 and > > dsa-2dwq x 15 as compatible, because the two mdevs consist equal resources. > > > > But, as it's a burden to upper layer, we agree that if this condition > > happens, we still treat the two as incompatible. > > > > To fix it, either the driver should expose dsa-1dwq only, or the target > > dsa-2dwq needs to be destroyed and reallocated via dsa-1dwq x 30. > > AFAIU, these are mdev types, aren't they? So, basically, any management > software needs to take care to use the matching mdev type on the target > system for device creation? or just do the simple thing of use the same mdev type on the source and dest. matching mdevtypes is not nessiarly trivial. we could do that but we woudl have to do that in python rather then sql so it would be slower to do at least today. we dont currently have the ablity to say the resouce provider must have 1 of these set of traits. just that we must have a specific trait. this is a feature we have disucssed a couple of times and delayed untill we really really need it but its not out of the question that we could add it for this usecase. i suspect however we would do exact match first and explore this later after the inital mdev migration works.

> still, I'd like to put it more explicitly to make ensure it's not missed: > the reason we want to specify compatible_type as a trait and check > whether target compatible_type is the superset of source > compatible_type is for the consideration of backward compatibility. > e.g. > an old generation device may have a mdev type xxx-v4-yyy, while a newer > generation device may be of mdev type xxx-v5-yyy. > with the compatible_type traits, the old generation device is still > able to be regarded as compatible to newer generation device even their > mdev types are not equal. If you want to support migration from v4 to v5, can't the (presumably newer) driver that supports v5 simply register the v4 type as well, so that the mdev can be created as v4? (Just like QEMU versioned machine types work.)

On Wed, 9 Sep 2020 10:13:09 +0800 Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > still, I'd like to put it more explicitly to make ensure it's not missed: > > > the reason we want to specify compatible_type as a trait and check > > > whether target compatible_type is the superset of source > > > compatible_type is for the consideration of backward compatibility. > > > e.g. > > > an old generation device may have a mdev type xxx-v4-yyy, while a newer > > > generation device may be of mdev type xxx-v5-yyy. > > > with the compatible_type traits, the old generation device is still > > > able to be regarded as compatible to newer generation device even their > > > mdev types are not equal. > > > If you want to support migration from v4 to v5, can't the (presumably > > newer) driver that supports v5 simply register the v4 type as well, so > > that the mdev can be created as v4? (Just like QEMU versioned machine > > types work.) > yes, it should work in some conditions. > but it may not be that good in some cases when v5 and v4 in the name string > of mdev type identify hardware generation (e.g. v4 for gen8, and v5 for > gen9) > e.g. > (1). when src mdev type is v4 and target mdev type is v5 as > software does not support it initially, and v4 and v5 identify hardware > differences. My first hunch here is: Don't introduce types that may be compatible later. Either make them compatible, or make them distinct by design, and possibly add a different, compatible type later. > then after software upgrade, v5 is now compatible to v4, should the > software now downgrade mdev type from v5 to v4? > not sure if moving hardware generation info into a separate attribute > from mdev type name is better. e.g. remove v4, v5 in mdev type, while use > compatible_pci_ids to identify compatibility. If the generations are compatible, don't mention it in the mdev type. If they aren't, use distinct types, so that management software doesn't have to guess. At least that would be my naive approach here.

> (2) name string of mdev type is composed by "driver_name + type_name". > in some devices, e.g. qat, different generations of devices are binding to > drivers of different names, e.g. "qat-v4", "qat-v5". > then though type_name is equal, mdev type is not equal. e.g. > "qat-v4-type1", "qat-v5-type1". I guess that shows a shortcoming of that "driver_name + type_name" approach? Or maybe I'm just confused.

On Thu, 10 Sep 2020 13:50:11 +0100 Sean Mooney <smooney(a)redhat.com&gt; wrote: > On Thu, 2020-09-10 at 14:38 +0200, Cornelia Huck wrote: > > On Wed, 9 Sep 2020 10:13:09 +0800 > > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > > > > > still, I'd like to put it more explicitly to make ensure it's not missed: > > > > > the reason we want to specify compatible_type as a trait and check > > > > > whether target compatible_type is the superset of source > > > > > compatible_type is for the consideration of backward compatibility. > > > > > e.g. > > > > > an old generation device may have a mdev type xxx-v4-yyy, while a newer > > > > > generation device may be of mdev type xxx-v5-yyy. > > > > > with the compatible_type traits, the old generation device is still > > > > > able to be regarded as compatible to newer generation device even their > > > > > mdev types are not equal. > > > > > > > > If you want to support migration from v4 to v5, can't the (presumably > > > > newer) driver that supports v5 simply register the v4 type as well, so > > > > that the mdev can be created as v4? (Just like QEMU versioned machine > > > > types work.) > > > > > > yes, it should work in some conditions. > > > but it may not be that good in some cases when v5 and v4 in the name string > > > of mdev type identify hardware generation (e.g. v4 for gen8, and v5 for > > > gen9) > > > > > > e.g. > > > (1). when src mdev type is v4 and target mdev type is v5 as > > > software does not support it initially, and v4 and v5 identify hardware > > > differences. > > > > My first hunch here is: Don't introduce types that may be compatible > > later. Either make them compatible, or make them distinct by design, > > and possibly add a different, compatible type later. > > > > > then after software upgrade, v5 is now compatible to v4, should the > > > software now downgrade mdev type from v5 to v4? > > > not sure if moving hardware generation info into a separate attribute > > > from mdev type name is better. e.g. remove v4, v5 in mdev type, while use > > > compatible_pci_ids to identify compatibility. > > > > If the generations are compatible, don't mention it in the mdev type. > > If they aren't, use distinct types, so that management software doesn't > > have to guess. At least that would be my naive approach here. > yep that is what i would prefer to see too. > > > > > > > > (2) name string of mdev type is composed by "driver_name + type_name". > > > in some devices, e.g. qat, different generations of devices are binding to > > > drivers of different names, e.g. "qat-v4", "qat-v5". > > > then though type_name is equal, mdev type is not equal. e.g. > > > "qat-v4-type1", "qat-v5-type1". > > > > I guess that shows a shortcoming of that "driver_name + type_name" > > approach? Or maybe I'm just confused. > yes i really dont like haveing the version in the mdev-type name > i would stongly perfger just qat-type-1 wehere qat is just there as a way of namespacing. > although symmetric-cryto, asymmetric-cryto and compression woudl be a better name then type-1, type-2, type-3 if > that is what they would end up mapping too. e.g. qat-compression or qat-aes is a much better name then type-1 > higher layers of software are unlikely to parse the mdev names but as a human looking at them its much eaiser to > understand if the names are meaningful. the qat prefix i think is important however to make sure that your mdev-types > dont colide with other vendeors mdev types. so i woudl encurage all vendors to prefix there mdev types with etiher the > device name or the vendor. +1 to all this, the mdev type is meant to indicate a software compatible interface, if different hardware versions can be software compatible, then don't make the job of finding a compatible device harder. The full type is a combination of the vendor driver name plus the vendor provided type name specifically in order to provide a type namespace per vendor driver. That's done at the mdev core level. Thanks,

From: Cornelia Huck <cohuck(a)redhat.com&gt; Sent: Friday, September 11, 2020 6:08 PM On Fri, 11 Sep 2020 08:56:00 +0800 Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > On Thu, Sep 10, 2020 at 12:02:44PM -0600, Alex Williamson wrote: > > On Thu, 10 Sep 2020 13:50:11 +0100 > > Sean Mooney <smooney(a)redhat.com&gt; wrote: > > > > > On Thu, 2020-09-10 at 14:38 +0200, Cornelia Huck wrote: > > > > On Wed, 9 Sep 2020 10:13:09 +0800 > > > > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > > > > > > > > > still, I'd like to put it more explicitly to make ensure it's not missed: > > > > > > > the reason we want to specify compatible_type as a trait and check > > > > > > > whether target compatible_type is the superset of source > > > > > > > compatible_type is for the consideration of backward compatibility. > > > > > > > e.g. > > > > > > > an old generation device may have a mdev type xxx-v4-yyy, while a newer > > > > > > > generation device may be of mdev type xxx-v5-yyy. > > > > > > > with the compatible_type traits, the old generation device is still > > > > > > > able to be regarded as compatible to newer generation device even their > > > > > > > mdev types are not equal. > > > > > > > > > > > > If you want to support migration from v4 to v5, can't the (presumably > > > > > > newer) driver that supports v5 simply register the v4 type as well, so > > > > > > that the mdev can be created as v4? (Just like QEMU versioned machine > > > > > > types work.) > > > > > > > > > > yes, it should work in some conditions. > > > > > but it may not be that good in some cases when v5 and v4 in the name string > > > > > of mdev type identify hardware generation (e.g. v4 for gen8, and v5 for > > > > > gen9) > > > > > > > > > > e.g. > > > > > (1). when src mdev type is v4 and target mdev type is v5 as > > > > > software does not support it initially, and v4 and v5 identify hardware > > > > > differences. > > > > > > > > My first hunch here is: Don't introduce types that may be compatible > > > > later. Either make them compatible, or make them distinct by design, > > > > and possibly add a different, compatible type later. > > > > > > > > > then after software upgrade, v5 is now compatible to v4, should the > > > > > software now downgrade mdev type from v5 to v4? > > > > > not sure if moving hardware generation info into a separate attribute > > > > > from mdev type name is better. e.g. remove v4, v5 in mdev type, while use > > > > > compatible_pci_ids to identify compatibility. > > > > > > > > If the generations are compatible, don't mention it in the mdev type. > > > > If they aren't, use distinct types, so that management software doesn't > > > > have to guess. At least that would be my naive approach here. [*] > > > yep that is what i would prefer to see too. > > > > > > > > > > > > > > (2) name string of mdev type is composed by "driver_name + type_name". > > > > > in some devices, e.g. qat, different generations of devices are binding to > > > > > drivers of different names, e.g. "qat-v4", "qat-v5". > > > > > then though type_name is equal, mdev type is not equal. e.g. > > > > > "qat-v4-type1", "qat-v5-type1". > > > > > > > > I guess that shows a shortcoming of that "driver_name + type_name" > > > > approach? Or maybe I'm just confused. > > > yes i really dont like haveing the version in the mdev-type name > > > i would stongly perfger just qat-type-1 wehere qat is just there as a way of namespacing. > > > although symmetric-cryto, asymmetric-cryto and compression woudl be a better name then type-1, type-2, type-3 if > > > that is what they would end up mapping too. e.g. qat-compression or qat-aes is a much better name then type-1 > > > higher layers of software are unlikely to parse the mdev names but as a human looking at them its much eaiser to > > > understand if the names are meaningful. the qat prefix i think is important however to make sure that your mdev-types > > > dont colide with other vendeors mdev types. so i woudl encurage all vendors to prefix there mdev types with etiher the > > > device name or the vendor. > > > > +1 to all this, the mdev type is meant to indicate a software > > compatible interface, if different hardware versions can be software > > compatible, then don't make the job of finding a compatible device > > harder. The full type is a combination of the vendor driver name plus > > the vendor provided type name specifically in order to provide a type > > namespace per vendor driver. That's done at the mdev core level. > > Thanks, > > hi Alex, > got it. so do you suggest that vendors use consistent driver name over > generations of devices? > for qat, they create different modules for each generation. This > practice is not good if they want to support migration between devices > of different generations, right? Even if they create different modules, I'd assume that they have some kind of core with common functionality. I'd assume that as long they do any type registrations satisfying [*] in the core, they should be good. > and can I understand that we don't want support of migration between > different mdev types even in future ? From my point of view, I don't see anything that migration between different mdev types would buy that is worth the complexity in finding out which mdev types are actually compatible.

To: Zhao, Yan Y <yan.y.zhao(a)intel.com&gt; Cc: Sean Mooney <smooney(a)redhat.com>; Cornelia Huck <cohuck(a)redhat.com>; Daniel P.Berrangé <berrange(a)redhat.com>; kvm(a)vger.kernel.org; libvir-list(a)redhat.com; Jason Wang <jasowang(a)redhat.com>; qemu-devel(a)nongnu.org; kwankhede(a)nvidia.com; eauger(a)redhat.com; Wang, Xin-ran <xin- ran.wang(a)intel.com>; corbet(a)lwn.net; openstack- discuss(a)lists.openstack.org; Feng, Shaohe <shaohe.feng(a)intel.com>; Tian, Kevin <kevin.tian(a)intel.com>; Parav Pandit <parav(a)mellanox.com>; Ding, Jian-feng <jian-feng.ding(a)intel.com>; dgilbert(a)redhat.com; zhenyuw(a)linux.intel.com; Xu, Hejie <hejie.xu(a)intel.com>; bao.yumeng(a)zte.com.cn; intel-gvt-dev(a)lists.freedesktop.org; eskultet(a)redhat.com; Jiri Pirko <jiri(a)mellanox.com>; dinechin(a)redhat.com; devel(a)ovirt.org Subject: Re: device compatibility interface for live migration with assigned devices On Fri, 11 Sep 2020 08:56:00 +0800 Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > On Thu, Sep 10, 2020 at 12:02:44PM -0600, Alex Williamson wrote: > > On Thu, 10 Sep 2020 13:50:11 +0100 > > Sean Mooney <smooney(a)redhat.com&gt; wrote: > > > > > On Thu, 2020-09-10 at 14:38 +0200, Cornelia Huck wrote: > > > > On Wed, 9 Sep 2020 10:13:09 +0800 > > > > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > > > > > > > > > still, I'd like to put it more explicitly to make ensure it's not missed: > > > > > > > the reason we want to specify compatible_type as a trait and check > > > > > > > whether target compatible_type is the superset of source > > > > > > > compatible_type is for the consideration of backward compatibility. > > > > > > > e.g. > > > > > > > an old generation device may have a mdev type xxx-v4-yyy, while a newer > > > > > > > generation device may be of mdev type xxx-v5-yyy. > > > > > > > with the compatible_type traits, the old generation device is still > > > > > > > able to be regarded as compatible to newer generation device even their > > > > > > > mdev types are not equal. > > > > > > > > > > > > If you want to support migration from v4 to v5, can't the (presumably > > > > > > newer) driver that supports v5 simply register the v4 type as well, so > > > > > > that the mdev can be created as v4? (Just like QEMU versioned machine > > > > > > types work.) > > > > > > > > > > yes, it should work in some conditions. > > > > > but it may not be that good in some cases when v5 and v4 in the name string > > > > > of mdev type identify hardware generation (e.g. v4 for gen8, and v5 for > > > > > gen9) > > > > > > > > > > e.g. > > > > > (1). when src mdev type is v4 and target mdev type is v5 as > > > > > software does not support it initially, and v4 and v5 identify hardware > > > > > differences. > > > > > > > > My first hunch here is: Don't introduce types that may be compatible > > > > later. Either make them compatible, or make them distinct by design, > > > > and possibly add a different, compatible type later. > > > > > > > > > then after software upgrade, v5 is now compatible to v4, should the > > > > > software now downgrade mdev type from v5 to v4? > > > > > not sure if moving hardware generation info into a separate attribute > > > > > from mdev type name is better. e.g. remove v4, v5 in mdev type, while use > > > > > compatible_pci_ids to identify compatibility. > > > > > > > > If the generations are compatible, don't mention it in the mdev type. > > > > If they aren't, use distinct types, so that management software doesn't > > > > have to guess. At least that would be my naive approach here. > > > yep that is what i would prefer to see too. > > > > > > > > > > > > > > (2) name string of mdev type is composed by "driver_name + type_name". > > > > > in some devices, e.g. qat, different generations of devices are binding to > > > > > drivers of different names, e.g. "qat-v4", "qat-v5". > > > > > then though type_name is equal, mdev type is not equal. e.g. > > > > > "qat-v4-type1", "qat-v5-type1". > > > > > > > > I guess that shows a shortcoming of that "driver_name + type_name" > > > > approach? Or maybe I'm just confused. > > > yes i really dont like haveing the version in the mdev-type name > > > i would stongly perfger just qat-type-1 wehere qat is just there as a way of namespacing. > > > although symmetric-cryto, asymmetric-cryto and compression woudl be a better name then type-1, type-2, type-3 if > > > that is what they would end up mapping too. e.g. qat-compression or qat-aes is a much better name then type-1 > > > higher layers of software are unlikely to parse the mdev names but as a human looking at them its much eaiser to > > > understand if the names are meaningful. the qat prefix i think is important however to make sure that your mdev-types > > > dont colide with other vendeors mdev types. so i woudl encurage all vendors to prefix there mdev types with etiher the > > > device name or the vendor. > > > > +1 to all this, the mdev type is meant to indicate a software > > compatible interface, if different hardware versions can be software > > compatible, then don't make the job of finding a compatible device > > harder. The full type is a combination of the vendor driver name plus > > the vendor provided type name specifically in order to provide a type > > namespace per vendor driver. That's done at the mdev core level. > > Thanks, > > hi Alex, > got it. so do you suggest that vendors use consistent driver name over > generations of devices? > for qat, they create different modules for each generation. This > practice is not good if they want to support migration between devices > of different generations, right? > > and can I understand that we don't want support of migration between > different mdev types even in future ? You need to balance your requirements here. If you're creating different drivers per generation, that suggests different device APIs, which is a legitimate use case for different mdev types. However if you're expecting migration compatibility, that must be seamless to the guest, therefore the device API must be identical. That suggests that migration between different types doesn't make much sense. If a new generation device wants to expose a new mdev type with new features or device API, yet also support migration with an older mdev type, why wouldn't it simply expose both the old and the new type?

It seems much more supportable to simply instantiate an instance of the older type than to create an instance of the new type, which by the contents of the migration stream is configured to behave as the older type. The latter sounds very difficult to test. A challenge when we think about migration between different types, particularly across different vendor drivers, is that the migration stream is opaque, it's device and vendor specific. Therefore it's not only difficult for userspace to understand the compatibility matrix, but also to actually support it in software, maintaining version and bug compatibility across different drivers. It's clearly much, much easier when the same code base (and thus the same mdev type) is producing and consuming the migration data. Thanks, Alex

To: Zeng, Xin <xin.zeng(a)intel.com&gt; Cc: Zhao, Yan Y <yan.y.zhao(a)intel.com>; Sean Mooney <smooney(a)redhat.com>; Cornelia Huck <cohuck(a)redhat.com>; Daniel P.Berrangé <berrange(a)redhat.com>; kvm(a)vger.kernel.org; libvir- list(a)redhat.com; Jason Wang <jasowang(a)redhat.com>; qemu- devel(a)nongnu.org; kwankhede(a)nvidia.com; eauger(a)redhat.com; Wang, Xin-ran <xin-ran.wang(a)intel.com>; corbet(a)lwn.net; openstack- discuss(a)lists.openstack.org; Feng, Shaohe <shaohe.feng(a)intel.com>; Tian, Kevin <kevin.tian(a)intel.com>; Parav Pandit <parav(a)mellanox.com>; Ding, Jian-feng <jian-feng.ding(a)intel.com>; dgilbert(a)redhat.com; zhenyuw(a)linux.intel.com; Xu, Hejie <hejie.xu(a)intel.com>; bao.yumeng(a)zte.com.cn; intel-gvt-dev(a)lists.freedesktop.org; eskultet(a)redhat.com; Jiri Pirko <jiri(a)mellanox.com>; dinechin(a)redhat.com; devel(a)ovirt.org Subject: Re: device compatibility interface for live migration with assigned devices On Mon, 14 Sep 2020 13:48:43 +0000 "Zeng, Xin" <xin.zeng(a)intel.com&gt; wrote: > On Saturday, September 12, 2020 12:52 AM > Alex Williamson <alex.williamson(a)redhat.com&gt; wrote: > > To: Zhao, Yan Y <yan.y.zhao(a)intel.com&gt; > > Cc: Sean Mooney <smooney(a)redhat.com>; Cornelia Huck > > <cohuck(a)redhat.com>; Daniel P.Berrangé <berrange(a)redhat.com>; > > kvm(a)vger.kernel.org; libvir-list(a)redhat.com; Jason Wang > > <jasowang(a)redhat.com>; qemu-devel(a)nongnu.org; > > kwankhede(a)nvidia.com; eauger(a)redhat.com; Wang, Xin-ran <xin- > > ran.wang(a)intel.com>; corbet(a)lwn.net; openstack- > > discuss(a)lists.openstack.org; Feng, Shaohe <shaohe.feng(a)intel.com>; Tian, > > Kevin <kevin.tian(a)intel.com>; Parav Pandit <parav(a)mellanox.com>; Ding, > > Jian-feng <jian-feng.ding(a)intel.com>; dgilbert(a)redhat.com; > > zhenyuw(a)linux.intel.com; Xu, Hejie <hejie.xu(a)intel.com>; > > bao.yumeng(a)zte.com.cn; intel-gvt-dev(a)lists.freedesktop.org; > > eskultet(a)redhat.com; Jiri Pirko <jiri(a)mellanox.com>; dinechin(a)redhat.com; > > devel(a)ovirt.org > > Subject: Re: device compatibility interface for live migration with assigned > > devices > > > > On Fri, 11 Sep 2020 08:56:00 +0800 > > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > > > On Thu, Sep 10, 2020 at 12:02:44PM -0600, Alex Williamson wrote: > > > > On Thu, 10 Sep 2020 13:50:11 +0100 > > > > Sean Mooney <smooney(a)redhat.com&gt; wrote: > > > > > > > > > On Thu, 2020-09-10 at 14:38 +0200, Cornelia Huck wrote: > > > > > > On Wed, 9 Sep 2020 10:13:09 +0800 > > > > > > Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > > > > > > > > > > > > > > > still, I'd like to put it more explicitly to make ensure it's not > > missed: > > > > > > > > > the reason we want to specify compatible_type as a trait and > > check > > > > > > > > > whether target compatible_type is the superset of source > > > > > > > > > compatible_type is for the consideration of backward > > compatibility. > > > > > > > > > e.g. > > > > > > > > > an old generation device may have a mdev type xxx-v4-yyy, > > while a newer > > > > > > > > > generation device may be of mdev type xxx-v5-yyy. > > > > > > > > > with the compatible_type traits, the old generation device is still > > > > > > > > > able to be regarded as compatible to newer generation device > > even their > > > > > > > > > mdev types are not equal. > > > > > > > > > > > > > > > > If you want to support migration from v4 to v5, can't the > > (presumably > > > > > > > > newer) driver that supports v5 simply register the v4 type as well, > > so > > > > > > > > that the mdev can be created as v4? (Just like QEMU versioned > > machine > > > > > > > > types work.) > > > > > > > > > > > > > > yes, it should work in some conditions. > > > > > > > but it may not be that good in some cases when v5 and v4 in the > > name string > > > > > > > of mdev type identify hardware generation (e.g. v4 for gen8, and v5 > > for > > > > > > > gen9) > > > > > > > > > > > > > > e.g. > > > > > > > (1). when src mdev type is v4 and target mdev type is v5 as > > > > > > > software does not support it initially, and v4 and v5 identify > > hardware > > > > > > > differences. > > > > > > > > > > > > My first hunch here is: Don't introduce types that may be compatible > > > > > > later. Either make them compatible, or make them distinct by design, > > > > > > and possibly add a different, compatible type later. > > > > > > > > > > > > > then after software upgrade, v5 is now compatible to v4, should the > > > > > > > software now downgrade mdev type from v5 to v4? > > > > > > > not sure if moving hardware generation info into a separate > > attribute > > > > > > > from mdev type name is better. e.g. remove v4, v5 in mdev type, > > while use > > > > > > > compatible_pci_ids to identify compatibility. > > > > > > > > > > > > If the generations are compatible, don't mention it in the mdev type. > > > > > > If they aren't, use distinct types, so that management software > > doesn't > > > > > > have to guess. At least that would be my naive approach here. > > > > > yep that is what i would prefer to see too. > > > > > > > > > > > > > > > > > > > > (2) name string of mdev type is composed by "driver_name + > > type_name". > > > > > > > in some devices, e.g. qat, different generations of devices are > > binding to > > > > > > > drivers of different names, e.g. "qat-v4", "qat-v5". > > > > > > > then though type_name is equal, mdev type is not equal. e.g. > > > > > > > "qat-v4-type1", "qat-v5-type1". > > > > > > > > > > > > I guess that shows a shortcoming of that "driver_name + type_name" > > > > > > approach? Or maybe I'm just confused. > > > > > yes i really dont like haveing the version in the mdev-type name > > > > > i would stongly perfger just qat-type-1 wehere qat is just there as a way > > of namespacing. > > > > > although symmetric-cryto, asymmetric-cryto and compression woudl > > be a better name then type-1, type-2, type-3 if > > > > > that is what they would end up mapping too. e.g. qat-compression or > > qat-aes is a much better name then type-1 > > > > > higher layers of software are unlikely to parse the mdev names but as a > > human looking at them its much eaiser to > > > > > understand if the names are meaningful. the qat prefix i think is > > important however to make sure that your mdev-types > > > > > dont colide with other vendeors mdev types. so i woudl encurage all > > vendors to prefix there mdev types with etiher the > > > > > device name or the vendor. > > > > > > > > +1 to all this, the mdev type is meant to indicate a software > > > > compatible interface, if different hardware versions can be software > > > > compatible, then don't make the job of finding a compatible device > > > > harder. The full type is a combination of the vendor driver name plus > > > > the vendor provided type name specifically in order to provide a type > > > > namespace per vendor driver. That's done at the mdev core level. > > > > Thanks, > > > > > > hi Alex, > > > got it. so do you suggest that vendors use consistent driver name over > > > generations of devices? > > > for qat, they create different modules for each generation. This > > > practice is not good if they want to support migration between devices > > > of different generations, right? > > > > > > and can I understand that we don't want support of migration between > > > different mdev types even in future ? > > > > You need to balance your requirements here. If you're creating > > different drivers per generation, that suggests different device APIs, > > which is a legitimate use case for different mdev types. However if > > you're expecting migration compatibility, that must be seamless to the > > guest, therefore the device API must be identical. That suggests that > > migration between different types doesn't make much sense. If a new > > generation device wants to expose a new mdev type with new features or > > device API, yet also support migration with an older mdev type, why > > wouldn't it simply expose both the old and the new type? > > I think all of these make sense, and I am assuming it's also reasonable and > common that each generation of device has a separate device driver module. > On the other hand, please be aware that, the mdev type is consisted of the > driver name of the mdev's parent device and the name of a mdev type which > the device driver specifies. > If a new generation device driver wants to expose an old mdev type, it has to > register the same driver name as the old one so that the mdev type could > be completely same. This doesn't make sense as a) driver name usually is > unique for a device driver module. b) If a system has both these two > generation devices, once one generation device driver is loaded, the other > is not allowed to be loaded due to the same driver name. > So to allow a new generation device to simply expose the old mdev type for > compatibility like you proposed, is it possible to create the mdev type by > another approach, e.g. device driver creates its own namespace for the > mdev type instead of mdev's parent device driver name being used currently? TBH, I don't think that it's reasonable or common that different drivers are used for each generation of hardware. Drivers typically evolve to support new generations of hardware, often sharing significant code between generations. When we deal with mdev migration, we have an opaque data stream managed by the driver, our default assumption is therefore that the driver plays a significant role in the composition of that data stream. I'm not ruling out that we should support some form of compatibility between types, but in the described scenario it seems the development model of the vendor drivers is not conducive to the most obvious form of compatibility checking. Thanks,

Alex