Re: [libvirt] [Qemu-devel] [PATCH v7 0/4] Add Mediated device support
On 09/02/2016 05:48 PM, Paolo Bonzini wrote:
On 02/09/2016 20:33, Kirti Wankhede wrote:
> <Alex> We could even do:
>>>
>>> echo $UUID1:$GROUPA > create
>>>
>>> where $GROUPA is the group ID of a previously created mdev device into
>>> which $UUID1 is to be created and added to the same group.
> </Alex>
>From the point of view of libvirt, I think I prefer Alex's idea.
<group> could be an additional element in the nodedev-create XML:
<device>
<name>my-vgpu</name>
<parent>pci_0000_86_00_0</parent>
<capability type='mdev'>
<type id='11'/>
<uuid>0695d332-7831-493f-9e71-1c85c8911a08</uuid>
<group>group1</group>
</capability>
</device>
(should group also be a UUID?)
As long as create_group handles all the work and all libvirt does is
call it, get the return status/error, and handle deleting the vGPU on
error, then I guess it's doable.
Alternatively having multiple <type id='#'> in the XML and performing a
single *mdev/create_group is an option. I suppose it all depends on the
arguments to create_group and the expected output and how that's
expected to be used.
That is, what is the "output" from create_group that gets added to the
domain XML? How is that found? Also, once the domain is running can a
vGPU be added to the group? Removed? What allows/prevents?
Since John brought up the topic of minimal XML, in this case it will be
like this:
<device>
<name>my-vgpu</name>
<parent>pci_0000_86_00_0</parent>
<capability type='mdev'>
<type id='11'/>
</capability>
</device>
The uuid will be autogenerated by libvirt and if there's no <group> (as
is common for VMs with only 1 vGPU) it will be a single-device group.
The <name> could be ignored as it seems existing libvirt code wants to
generate a name via udevGenerateDeviceName for other devices. I haven't
studied it long enough, but I believe that's how those pci_####* names
created.
John