Recently I re-installed kubuntu 20.10 onto the host machine from scratch. I also decided to try the bleeding-edge build of Looking Glass.
Looking glass mostly works well (on xorg, wayland on plasma is still pretty rough) except I get screen corruption after task-switching away from the full-screen viewer (in full-screen mode) and back again.
This is how I typically work - I start a windows gpu-passthrough vm and the viewer in full-screen mode but with capture disabled. Then I have a keyboard key-binding mapped on the host to ‘minimize-window’. This enables me to tap the key to jump out of the gpu-vm session to do other things, then click on the running viewer’s icon on the host’s task manager or alt-tab to jump back in. For me this is pretty much the ideal setup for the work I do.
However there appears to be a bug in the current bleeding-edge build. Sometimes (not always) after switching away then back to the full-screen viewer I see flickering horizontal bands of graphics corruption triggered by screen updates in the guest vm. See attached video for an example.
[On Wayland on the other hand, it’s a mess when using kubuntu. Results were much better back on ubuntu 20.04+wayland so this is probably a wayland on kubuntu bug and not looking glass but I see what appear to be a lot of lost invalidate-rect’s (reminiscent of my old windows 3.1 programming days) but I’m fine using x11 on the host for now so this is not really an problem, just a fyi field report.]
However, I’d like to slip in a small feature request: I think it would be great to have a key mapped in looking glass to minimize viewer. This way the user could enable key-capture mode and yet escape the vm session when desired without having to quit the viewer with ScrLk-Q or disable capture and task-switch.
In general I’ really liking the updates. Overhead is way down and frame-rates are way up vs. B2 which I was on before. It all runs really smoothly on my iGPU host + passthru-gpu guest setup, generally getting ~60fps when orbiting pretty complex cad models. I’m going to try to stay on the leading-edge build in the hope I can give feedback so we can fix this minor issue quickly. @gnif, I’m at your disposal to test/etc if/when you can get to it.
Last but not least, thanks to all the hard work all the developers have put into looking glass. It’s looking great. Check your paypal, progress donation incoming.
EDIT: changing title, update: looks like I may be forced to go back to the B2+ version that ran pretty well on this system before.
It turns out that the screen corruption isn’t related to task switching, was pretty random and I thought there was a relationship to task switching but now for some unknown reason it happens all the time even on a fresh reboot & no task-switching involved.
Adding egl:vsync to the viewer command line leads to behavior similar to running under wayland where screen updates are incomplete, for example black-screen except where updated where the mouse pointer has moved over.
Anyone have suggestions for getting something working here before I go back to an earlier build?
Ok I figured out the problem:
GRUB_CMDLINE_LINUX_DEFAULT="… iommu=pt …" was misspelled.
After updating grub and rebooting the problem appears 100% fixed in the looking-glass viewer. Still seeing minor graphic animation glitches on the host when the viewer is running but it’s very minor.