[libvirt] [PATCH] qemu: use 'bochs' video type by default for UEFI domains

[Gerd Hoffmann]

  Hi,

> Incidentally, and I haven't followed this closely so apologies if I'm
> asking a silly question, if the point of bochs-display is to have a
> video device without legacy VGA emulation then why aren't we using
> the existing virtio-gpu, which has been around a lot longer and has
> better support throughout the stack, instead?

Well, virtio-gpu (on x86) actually is "-device virtio-vga".  That comes
with legacy VGA emulation, for the boot display ...

For UEFI guests with virtio-gpu support it is possible to use "-display
virtio-gpu-pci" instead (simliar to arm).  Only drawback is that you
can't have a EFI GOB with virtio-gpu-pci, so efifb doesn't work.  Linux
kernel console shows up after the virtio-gpu driver loads, which is
rather late compared to efifb.

For UEFI guests without virtio-gpu support "-device virtio-gpu-pci" will
not work due to the lack of EFI GOB support.  For these guests
"-display bochs-display" should preferred over "-device VGA", to get rid
of the unused legacy VGA emulation (and thereby reduce the attack
surface).

Also note that bochs-display can be plugged into pcie slots (that is
true for virtio-gpu-pci too btw).

Not sure whenever implementing this works better in libvirt or
libosinfo.

cheers,
  Gerd