intel vgpu & spice & cursor

[Gerd Hoffmann]

  Hi,

We need to figure a way to handle intel vgpu with spice, especially how
to handle the cursor.

What we'll get from the vgpu is two dma-bufs:  One for the primary
plane (aka guest display), one for the cursor plane.  We also get the
position of the cursor.  We do *not* get the hotspot of the cursor.

The latter implies client mouse mode isn't going to work, so we need
some other way to render the cursor.  I see basically two options:

  (a) Update spice-server API (and probably spice protocol too),
      add a call (or two) to pass on cursor dmabuf and position.

  (b) Create a new dma-buf in qemu, render guest display with cursor
      to it, pass *that* to spice-server.

I think (a) would be the better choice.  It gives more flexibility to
the spice client, for example it would be possible to create a drm-
based spice client which simply maps the guest planes to a host
scanout.  I think it'll also have less overhead as qemu has no need to
touch the dma-bufs then, it just passes on the fds.

But option (b) wouldn't be a big deal either.  qemu must handle that
anyway, for the gtk and sdl UIs, so supporting it for spice too would
be easy.

Comments?

cheers,
  Gerd