Error: unhandled exception: unsupported partial overlap

[Jamin W. Collins]

Periodically, I find that I am unable to open the spice display to one of my virtual machines using the spicec cli (see below). When this happens I am still able to access the display using virt-manager.

$ virsh domdisplay 1
spice://127.0.0.1:5900

$ spicec -h 127.0.0.1 -p 5900
Error: unhandled exception: unsupported partial overlap

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: spice-client 0.12.2-0nocelt2expubuntu1.1
ProcVersionSignature: Ubuntu 3.8.0-28.41-generic 3.8.13.5
Uname: Linux 3.8.0-28-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.9.2-0ubuntu8.3
Architecture: amd64
Date: Thu Aug 15 07:34:54 2013
InstallationDate: Installed on 2009-12-21 (1332 days ago)
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release amd64 (20091027)
MarkForUpload: True
SourcePackage: spice
UpgradeStatus: Upgraded to raring on 2013-04-26 (111 days ago)

[Serge Hallyn (serge-hallyn)]

Thanks for reporting this bug. could you confirm whether you can also connect with 'spicy'?

Does /var/lib/libvirt/images/<domain>.log show anything useful?

[Serge Hallyn (serge-hallyn)]

Sorry, I meant /var/log/libvirt/qemu/<domain>.log.

[Jamin W. Collins (jcollins)]

$ spicec -h 127.0.0.1 -p 5900
Error: unhandled exception: unsupported partial overlap

$ spicy --uri spice://127.0.0.1:5900
GSpice-Message: main channel: opened
GSpice-Message: main channel: closed

Yes, it looks like spicy can handle the display when spicec fails with this error message.

I've found some additional information on how to replicate this problem. It seems this is triggered if you have two host displays of different resolutions mirrored, or partially overlapping.

$ xrandr -q
...
LVDS-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
   1920x1080 60.0*+ 50.0
...
DP-2 connected 1440x900+0+0 (normal left inverted right x axis y axis) 410mm x 256mm
   1440x900 59.9*+ 75.0 59.9
   1280x1024 75.0 60.0
   1024x768 75.0 70.1 60.0
   800x600 75.0 72.2 60.3 56.2
   640x480 75.0 72.8 59.9

If the host displays do not overlap at all, spicec works.

There doesn't appear to be anything in the domain log file for these display connection attempts.

[Serge Hallyn (serge-hallyn)]

Do you have a simple recipe for setting up such a VM (creating the second, overlapping display)?

Is it possible for you to test whether spicec on a saucy host still has the same problem? The version is slightly newer there.

[Jamin W. Collins (jcollins)]

It's not the VM (aka guest) that has the dual overlapping display, but rather the host machine. If the host's displays are overlapping or not a perfect 1:1 mirror, the error is returned when trying to view a guest's display using spicec. I'll see about trying to replicate this with a saucy live CD or something.

[Jamin W. Collins (jcollins)]

What further information is needed to make this report complete? I'll still see about replicating this with saucy, but I'm not sure how the report as it is is incomplete?

[Serge Hallyn (serge-hallyn)]

Ok so I have two monitors of different resolutions, usually non-mirrored. By "not a perfect 1:1 mirror", do you mean you go into the Displays configuration and specify 'mirror', with different resolutions?

[Jamin W. Collins (jcollins)]

I'm not sure how to do it via the Displays configuration, but have provided the xrandr output above. If the two monitors overlap in anyway without it being a perfect overlap the error is thrown.

I normally use arandr for display configuration.

If I open the Display configuration option under XFCE Settings Manager, I do not have the option to mirror to displays of different sizes. However, I do have the option to set the position as "Same as". The net effect of this is shown in the following xrandr output:

$ xrandr
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 16384 x 16384
VGA-0 connected 1280x1024+0+0 (normal left inverted right x axis y axis) 376mm x 301mm
   1280x1024 60.0*+ 76.0 75.0 72.0
   1152x864 75.0
   1024x768 75.0 70.1 60.0
   800x600 75.0 72.2 60.3
   640x480 75.0 72.8 59.9
   640x350 70.1
LVDS-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
   1920x1080 60.0*+ 50.0
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
DP-3 disconnected (normal left inverted right x axis y axis)
DP-4 disconnected (normal left inverted right x axis y axis)
DP-5 disconnected (normal left inverted right x axis y axis)

From the above you can see that both screens have different resolutions. The VGA-0 display is 1280x1024, while the LVDS-0 display is 1920x1080. However, both screens are positioned to start at 0x0. The result of this is that the two screens both display the same content for the 1280x1024 region.

This configuration causes the aforementioned error from spicec but not spicy:

$ spicec -h 127.0.0.1 -p 5900
Error: unhandled exception: unsupported partial overlap

$ spicy -h 127.0.0.1 -p 5900
GSpice-Message: main channel: opened

I'm also attaching a screen shot of the arandr display for this screen configuration

[Serge Hallyn (serge-hallyn)]

Thank you!

With arandr I was able to set overlapping displays and reproduce this.

Marking Triaged, but low priority due to spicy being a workaround.

Now I have no idea what could cause this...

[Serge Hallyn (serge-hallyn)]

(Note - reproduced in saucy, which is on 0.12.4, which is upstream latest)

[Serge Hallyn (serge-hallyn)]

Ah, here we go. client/x11/platform.ccp:crtc_overlap_test() explicitly disallows overlap.

So this appears to be a feature. I will send a msg to the mailing list to ask about this, as certainly there must have been a reason it was added.