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

On Thu, 2016-10-06 at 10:34 -0400, Laine Stump wrote: > > > +    <video> > > > +      <model type='virtio' heads='1' primary='yes'/> > > > +      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/> > >  > > I was initially baffled by this, because I expected it to > > be assigned to one of the available pcie-root-ports just > > like all the other virtio devices. > >  > > However, according to qemuDomainValidateDevicePCISlotsQ35() > > this is intentional, so I guess we're good :) >  > Actually, you bring up an interesting point in light of the "Should PCIe  > devices ever be placed directly on pcie-root?" debate on qemu-devel (I  > think it was in the thread about the PCI topology document that Marcel  > is writing). We currently always put the primary video device at 00:1  > just because "we always have", and it has the nice side effect of  > eliminating the need for legacy-PCI controllers. But in this one case  > the device is PCIe - to follow Marcel's recommendation of putting only  > legacy devices on pcie-root, we should be putting the virtio video  > device on a root-port. >  > As I recall, Marcel and Alex were the most vocal on this subject, so I'm  > Cc'ing them, with this bit of context - this patch auto-assigns the  > addresses for virtio devices to be on Express ports rather than legacy  > slots when appropriate, but there is a bit of Q35-specific code that  > overrides any of that and always places the primary video device at  > 00:01.0 - should we still do that for the primary video if it's virtio?  > Or should we put it behind a root-port? I don't think we ever got a reply... Bump? :)