5:11 a.m.
On 2020/7/20 下午6:39, Sean Mooney wrote:
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> 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
Well, if you try to build logic like introspection on top for a
sophisticated hardware, you probably need to have library on top. And
it's attribute per file is pretty inefficient.
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.
Kernel provides stable ABI for userspace, so it's not something that we
can't fix.
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.
I believe you can't change sysfs layout which is part of uABI. But as I
mentioned below, sysfs has several drawbacks. It's not harm to compare
between different approach when you start a new device management API.
Thanks
> - 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
>