Hi, > I think documenting the issue with VBE registers would be helpful. > Doing so with a recommendation for how to avoid the issue seems even > better. Would a recommendation to attach a device which supports VBE > to the Root Complex if VBE will be used by the guest make sense?
Yes. This affects all vga-compatible devices emulated by qemu except cirrus. > As you noted, applying the recommendation to all VGA compatible > devices may be too broad. I'm not sure whether it makes sense to > recommend attaching VGA compatible devices to the Root Complex to > avoid the complexity of the VGA exception bits, or if that is a > non-issue. In fact, if I understand correctly, it may make sense to > recommend attaching VGA compatible devices to separate PCI bridges if > the VM will have multiple VGA compatible devices so that the guest can > perform VGA arbitration. Yes. Also guest drivers for pci-attached might be confused in case they find a pcie gpu which is *not* in a pcie root port (which is impossible on physical hardware). take care, Gerd
