Hi On Tue, Feb 21, 2017 at 2:04 PM Gerd Hoffmann <kra...@redhat.com> wrote:
> Hi, > > > It's always 0, except with virtio. > > > > But I think virtio linux driver multi-monitor code would work with a > > single qemu head (like qxl, fwiw last time I checked, multi-monitor > > virtio+spice worked, with 3d too). > > > It seems to me the qemu "head" is quite different (lower-level) from > > spice "head". > > Well. spice/qxl supports two different ways to do multihead ... > > The first way is one display channel per head. Which maps nicely to > qemu heads. With qxl you'll use one qxl-vga device for the primary > display and one (or more) qxl devices for the secondary displays. I > think multihead with windows guests still works that way, but xorg > support for that (xinerama mode) is pretty bad. IIRC it needs manual > configuration, could also be recent xorg versions don't support it any > more. Dunno where we stand with wayland. > > The second way is a single display channel with a single, big surface > for all heads. Then -- with spice-agent help -- guest and client > negotiate which region of the big display gets scanned out to which > head. > > Multihead spice with virtio-gpu fundamentally works like the first way, > except that we have a single device with multiple heads (and display > channels) instead of multiple devices which have a single head each. > ok > > The use case I see for this is not so much multihead configuration. > With multiple display devices in your system, for example one intel-vgpu > and one emulated display device one could export only one of the two via > spice. > My understanding is that "head" will not work correctly with QXL (only head 0, but can be a multi-head QXL), but should do what you expect with virtio. thanks -- Marc-André Lureau
