Prime offloading from dGPU to iGPU causes distorted window content with Iris driver
I originally reported this here: https://bugs.freedesktop.org/show_bug.cgi?id=111400 But I suppose there is the possibility that this might be an xorg issue instead, so I'm reporting it here was well:
When I run "MESA_LOADER_DRIVER_OVERRIDE=iris DRI_PRIME=1 glxgears", the window content is highly stretched and thus looks garbled. This doesn't happen with some window sizes or aspect ratios though, and neither happens in maximized window or fullscreen mode. The display has typical 16:9 AR and 1440p resolution, it's connected to a RX 570 card using amdgpu driver (and xf86-video-amdgpu).
Tested with latest xorg-git and mesa-aco-git with commit b738bf069172ba08a087735061570ade4415041a. Happens with both xf86-video-intel and modesetting. No special xorg config involved.
Screenshot of the garbled default size window content: https://bugs.freedesktop.org/attachment.cgi?id=145060
Non-garbled window content in window maximized state: https://bugs.freedesktop.org/attachment.cgi?id=145061