[vfio-users] vga pass-thru and different gfx cards.

[Alex Williamson]

On Thu, Sep 10, 2015 at 12:57 PM, Torbjorn Jansson <
torbjorn.jansson at mbox200.swipnet.se> wrote:

> On 2015-09-10 20:48, Alex Williamson wrote:
>
>> On Thu, Sep 10, 2015 at 12:44 PM, Torbjorn Jansson <
>>
> torbjorn.jansson at mbox200.swipnet.se> wrote:
>>
>> On 2015-09-10 19:47, Alex Williamson wrote:
>>>
>>>> It's not clear to me why there are numerous reports of reset problems on
>>>> nvidia.  AFAIK, there's no broken hardware for nvidia in this space like
>>>> there is for AMD.  So if you're having reset problems, maybe it's
>>>> because
>>>> you're not binding both GPU and audio functions to vfio-pci and
>>>> therefore
>>>> vfio-pci can't do a bus reset on VM reset.  Maybe your motherboard
>>>> freaks
>>>> out on the bus reset.  Maybe it's a ROM issue like Blank suggests.
>>>>
>>>>
>>>> both functions are bound to pci-stub via grub command line using:
>>> pci-stub.ids=
>>>
>>> i forgot to say, i'm unfortunately stuck on linux kernel 4.0.4 due to
>>> issues with drivers for a dvb card.
>>> and my distro is fedora 22
>>>
>>
>>
>> pci-stub is only to prevent host driver from binding to the device,
>> eventually the device needs to get bound to vfio-pci or else you're not
>> using vfio to do the assignment.
>>
>
> ok, and that gets taken care of by libvirt when i power up the vm?
> i guess i have to check what driver is bound to the 2 functions once the
> vm is up and also check what happens once it is powered off.
>

If you're assigning both the audio and GPU functions then libvirt should
automatically re-bind them to vfio-pci, so long as you haven't specified
driver='kvm' for the hostdev entry.  You can always double check while the
VM is running or look in the libvirt log to make sure vfio-pci is being
used rather than pci-assign.
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