Any VM can make the entire screen gray and block keyboard/mouse input

[iprid23]

Qubes OS version
R4.0

Affected component(s) or functionality
Dom0 Xorg

Brief summary
Any VM can take over your screen(s) and make it hard to shut it down.
Not sure if this can exploited or it's just a possible Denial-Of-Service via annoyment.
Not sure if this will work with all GPUs either.

To Reproduce
Steps to reproduce the behavior:
_1. Make a Debian 9 based VM - testVM
_2. apt-get install compton
_3. compton -b --paint-on-overlay --unredir-if-possible --backend xr_glx_hybrid --glx-swap-method -1 --glx-no-stencil

Expected behavior
Only the windows belonging to the testVM should be affected.

Actual behavior
Your screen(s) turn gray. Pressing Ctrl-C or any other keys does nothing.

Screenshots
Could make some later.

Additional context
I've hit this when trying to use a compton for Video compositing inside a VM.

Solutions you've tried
Using Ctrl+Alt+F1-12 can give you another tty. From there you can do qvm-kill testVM.

[marmarek]

Duplicate of #4705