[libvirt] [PATCH v3 11/18] qemu: assign virtio devices to PCIe slot when appropriate

[Laine Stump]

On 11/16/2016 03:43 AM, Gerd Hoffmann wrote:
>    Hi,
>
>> I looked at "lspci" of a guest that has virtio-gpu directly connected to
>> pci-root, and found that it does show up as a legacy device in that
>> case, which I guess is what we want, right?
>>
>> Let's ask the author of virtio-gpu: Gerd, what is your opinion - when
>> using virtio-gpu as the primary video device, is it better to have it
>> directly plugged into 00:01.0 (i.e. a legacy integrated device)? Or is
>> it better to plug it into a pcie-root-port?
> virtio-vga or virtio-gpu-pci?

Ah, I didn't realize it until you asked, but libvirt uses virtio-vga for 
the primary video device (if model is set to "virtio"), and 
virtio-gpu-pci for any secondary video devices, and I had only specified 
a single device.

>
> virtio-gpu-pci should have zero issues in a pcie-root-port.
>
> For virtio-vga I'd tend to place it directly in 00:01.0, to avoid ioport
> access issues for the vga compatibility part of the device.

Okay, since this question is specifically for the primary video device, 
and vga compatibility is highly desired for that, I guess that's our 
answer - so the primary virtio video will stay on 00:01.0, and any 
additional virtio video devices will be plugged into a pcie-root-port.

Thanks!