https://bugs.freedesktop.org/show_bug.cgi?id=66961
--- Comment #4 from Knut Andre Tidemann knut.tidemann@gmail.com --- This might be due to a overheat issue.
I just got another GPU lockup while playing the game (after a few hours) and it did not cause the kernel OOPS/Bug in question, so everything went on as normal after the GPU recovered.
However, after a few minutes I lost the display (it went black). Logging in over SSH and checking the temperature sensor revealed that the radeon GPU reported 127.5C.
So unless someone else has seen this issue, I think it can be discarded.