Poor graphics performance even with Ubuntu guests

[Pedro Côrte-Real]

Virt-manager on Ubuntu 18.04 will use QXL as the video device for Ubuntu 16.04 guests (for example). At least with a 16.04 guest this results in a frozen screen when changing resolution. Switching to virtio drivers works better but GL enablement doesn't seem to work saying it's not supported. This results in extremely choppy youtube videos and doesn't include my laptops native 2560x1440 resolution as one of the options.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: virt-manager 1:1.5.1-0ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-29.31-generic 4.15.18
Uname: Linux 4.15.0-29-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Wed Aug 1 17:19:32 2018
InstallationDate: Installed on 2018-05-31 (62 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
SourcePackage: virt-manager
UpgradeStatus: No upgrade log present (probably fresh install)

[Christian Ehrhardt  (paelzer)]

Hi Pedro,
usually defaults in libvirt are aligned at max-compatibility not max-performance.
You can make qxl faster by ensuring you are using spice, but I think it is the default as well.
If you happen to know a better but still very compatible default setting I'd recommend to suggest to upstream and we try to follow as we can.

"Can Follow" is the second part of your request- virtio GL enablement. This is based on virgl which is rather new still. The first time we enabled in Debian plenty of things broke, now it is enabled there again but still shows issues (jsut one new yesterday I think). In addition it is not yet super-hardened yet and might be a guest-to-host exploitable risk which is part of the reason why to enable virgl we are still waiting to complete the MIR [1] at [2].
You are not the first to ask, and in fact I'm the one filing [2] and polling on it every now and then :-/

TL;DR:
- for the qxl default alternatives I'd recommend to discuss upstream
- for virgl help making it more secure and maybe give [2] a bump by adding a comment

I think the bug contains nothing new in the sense of a "bug to fix" in addition to those.
I'll set it to incomplete for now, if you happen to drive an upstream discussion on default please report back here with the link to the MailingList or their Bug tracker - so that one can find it from here.

[1]: https://wiki.ubuntu.com/MainInclusionProcess
[2]: https://bugs.launchpad.net/ubuntu/+source/virglrenderer/+bug/1657409

[Pedro Côrte-Real (pedrocr)]

virgl was more of a secondary point, as that requires guest support that doesn't even really exist in most cases. The QXL default does seem broken though. At least in Ubuntu 16.04 guests that leads to a broken display if you change the resolution. I guess that's a bug in the 16.04 xserver QXL driver. Virtio seems to work a bit better at least but also with poor performance. I'll figure out how to have that discussion upstream.

[Launchpad Janitor (janitor)]

[Expired for virt-manager (Ubuntu) because there has been no activity for 60 days.]