Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out

[Gerd Hoffmann <kraxel@redhat.com>]

  Hi,
  Hi,

> Minor improvements to stdvga actual help qxl (presumably).  qxl still
> provides a vga interface which is used when guest drivers aren't
> available.
> 
> It's not clear to me why it doesn't enable VBE but presumably if it did,
> then accelerations could be mapped through VBE.

QXL actually enables VBE.  And, yes, making qemu translate simple 2D
bitblits into spice rendering ops is possible.

Mixing direct framebuffer writes and bitblit ops will give you bad
performance though, so when going that route I suggest to store the
console font somewhere in vga memory, then use only blit ops to draw the
letters and scroll the console.

> Actually, Gerd et al have expressed interest in moving to a virtio-based
> device model for Spice in the past.

There are discussions about re-doing the guest/host interface (command
rings etc) now and then, by adding a qxl2 device (or maybe even extend
stdvga), dropping a bunch of backward compatibility stuff in qxl.c.

Sending the spice commands over virtio is certainly an option here.  I'm
not sure it is possible to drive virtio rings from userspace (Xorg
driver), but that issue should go away with the qxl kms driver in the works.

> I think done correctly, it could help bring graphics to other platforms
> like S390 where PCI doesn't exist and will never exist.

Yes.

cheers,
  Gerd