Created attachment 131340 [details]
dmesg dump (complete)
I experience random (relatively low occurrence ~ twice a week) graphic lockups.
Video is not updated, mouse is moving but no interaction is possible either with mouse or keyboard.
System is somewhat alive and I can login via ssh.
I attach a complete dmesg dump taken via ssh.
Attempting to kill xorg to restart it resulted in a complete lockup (ssh timed out) and I had to brutally power-cycle the machine.
System is an up-to-date debian testing (stretch).
At the time of freeze I had one VirtualBox client (Win7) open but inactive (window minimized).
I will be available to give further info, if required.