[Spice-devel] Multi-head Spice

[Jonathon Jongsma]

On Tue, 2017-02-28 at 16:19 +0100, Christophe de Dinechin wrote:
> > On 28 Feb 2017, at 15:37, Jonathon Jongsma <jjongsma at redhat.com>
> > wrote:
> > 
> > On Tue, 2017-02-28 at 10:29 +0100, Christophe de Dinechin wrote:
> > > > On 27 Feb 2017, at 23:18, Jonathon Jongsma <jjongsma at redhat.com
> > > > >
> > > > wrote:
> > > > 
> > > > On Mon, 2017-02-27 at 17:53 +0100, Christophe de Dinechin
> > > > wrote:
> > > > > I tried to setup a multi-head guest, but I’m having trouble
> > > > > getting
> > > > > multiple displays to work correctly
> > > > > 
> > > > > For Jonathon, the part that I had trouble with was adding
> > > > > “heads
> > > > > =
> > > > > ‘4’" to the video / QXL configuration. I don’t see it
> > > > > documented
> > > > > in
> > > > > https://www.spice-space.org/spice-user-
> > > > > manual.html#_multiple_monitor_support.
> > > > 
> > > > Yep, it's a fairly new feature. I'm working on additional
> > > > multi-
> > > > monitor 
> > > > documentation and will be sure to include that.
> > > 
> > > Thanks
> > > 
> > > > > For Christophe F, what I get with the configuration file
> > > > > http://p
> > > > > aste
> > > > > bin.com/FEXbjaE3 is shown in the following picture https://re
> > > > > dski
> > > > > ncat
> > > > > .wordpress.com/2017/02/27/learning-more-about-mesa/#jp-
> > > > > carousel-
> > > > > 1224.
> > > > > As far as I remember, this is pretty much a default
> > > > > configuration
> > > > > of
> > > > > Fedora 25 after install from the live CD. If I understand
> > > > > correctly,
> > > > > the difference with you is that I actually installed.
> > > > > 
> > > > > Does anybody else see this? If not, what could be wrong with
> > > > > my
> > > > > setup?
> > > > > 
> > > > 
> > > > I don't see anything obviously wrong with the configuration. If
> > > > you
> > > > close the spice client and immediately re-connect does it still
> > > > show
> > > > the same thing in both windows?
> > > 
> > > Yes. It reopens two windows, both with monitor 2.
> > > 
> > > 
> > > > Can you capture the debug output of running virt-viewer with
> > > > the --
> > > > debug and --spice-debug options while you enable the second
> > > > monitor?
> > > > That might give a clue about what's happening.
> > > 
> > > Attached. I find it suspicious that we only have surface id 0.
> > 
> > I didn't see an attachment. Maybe it was stripped because it was
> > too
> > big? Perhaps a pastebin somewhere would be easier?
> 
> It’s here: http://pastebin.com/EY0AjfHK
> 
> Thanks
> Christophe

So, I did manage to reproduce this now. I just created a new guest vm
and installed a fresh fedora25 and I finally observed the issue. I also
observed that sometimes the screen would flash back and forth between
the contents of screen 1 and the contents of screen 2. You can see a
video of that here:

https://youtu.be/aQhv9Q45ecM

The client is sending the appropriate config to the guest, but the
guest is incorrectly configuring the two displays at the same position
(0,0). The displays aren't actually mirrored, they're technically two
separate displays but they're both located at the same position on the
underlying surface. Pavel and Snir both mentioned on IRC that updating
packages on fedora25 fixed the problem, but I found that even after
updating everything on my new guest, I was still able to reproduce the
issue. I guess it needs more investigation to figure out which
component is at fault here.

Jonathon