[Kimchi-devel] Host Device Passthrough UI Task Discussion

[Zhou Zheng Sheng]

on 2014/07/21 16:25, Yu Xin Huo wrote:
> 1. generally, how many devices will be available?

Usually, on a personal laptop, there would be about 10 devices available.
On small servers, there would be more, maybe about 30 devices, including
the SCSI LUNs. In future we may want to support SR-IOV, in this case it
would be a lot more devices, probably several dozens of devices.

My current thought is to add a new window/dialog when adding a new
device. In the window we have two areas, one is for listing all
available devices, when the user click a device, we display the detail
information in the other area.

> 2. the already attached devices will always be a subset of available
> host devices, right?

Correct.

> 3. please add support to add multiple devices in one request?

I think this suggestion is nice. I just have a few concerns. Firstly the
underlying operation of adding a device is much slower than a request
round trip, so it may not save much time to adding multiple device in
one request. Another reason is that it seem the collections in Kimchi
back-end framework does not support creating multiple elements in one
request. Technically it's possible and simple to support this. I am just
worried about being different to other collection APIs may break the
consistency of the concept of current collection implementation.

> 
> The API design does not match current API style related to vm, please
> change it for consistency.
> 'devices' is just an attribute along with other vm attributes, should
> not take a separate url.
> Refer to API.md for current vm API design and follow it.
> change attribute name 'hostdevs' to 'devices', at vm level, it is just
> devices of the vm.
> 
> On 7/16/2014 2:33 PM, Zhou Zheng Sheng wrote:
>> Hi,
>>
>> As in Kimchi 1.3 TODO list
>> (https://github.com/kimchi-project/kimchi/wiki/Todo-1.3), there is a
>> task of passthrough support. It is to enable Kimchi to assign hos
>> devices directly to a VM, thus greately improve VM performance.
>> Currently we support assigning PCI device, USB device and SCSI LUN. For
>> example, we can assign an NIC to VM to improve guest network throughput,
>> or passthrough a USB camera to enable the guest OS to record video.
>>
>> The back-end patch also handles PCI device grouping (attach and detach
>> all devices in the same iommu group together) and provides some other
>> useful features. Since the due day is near, I think we can come up with
>> an easy and simple UI for 1.3, and mark this feature as experimental.
>> Then we improve it in future releases. So in this release we may only
>> expose PCI devices to user and don't mention the iommu grouping logic.
>>
>> For this version I think we may provide the following operations to the
>> user.
>>
>> In the VM edit window, initially, the user sees a list of PCI devices
>> already assigned to the VM. This maps to GET vms/VM_NAME/hostdevs.
>>
>> In edit mode, the user can detach device. This maps to DELETE
>> vms/VM_NAME/hostdevs/DEVICE_NAME.
>>
>> The user can also select device to attach to VM from a list. The listing
>> of eligible devices is mapped to GET
>> host/devices?_passthrough=true&_cap=pci.
>>
>> To attach a device, just POST a dict containing only the device name to
>> vms/VM_NAME/hostdevs.
>>
>> I think these operations forms a basic interaction to enable user to
>> consume this feature. It may be feasible to finish them before the due
>> day.
>>
> 
> 


-- 
Zhou Zheng Sheng / 周征晟
E-mail: zhshzhou at linux.vnet.ibm.com
Telephone: 86-10-82454397