(In reply to comment #2)
> I too get system hangs when watching a flash video in firefox. linux-3.8.13,
> libdrm, mesa etc. git. Screen simply becomes black (no signal) and machine
> is dead, leaving a hard reset as the only option. The dmesg is flooded with
> the following lines:
> 
> radeon 0000:01:00.0: GPU fault detected: 147 0x0d859002
> radeon 0000:01:00.0:   VM_CONTEXT1_PROTECTION_FAULT_ADDR   0x000012D8
> radeon 0000:01:00.0:   VM_CONTEXT1_PROTECTION_FAULT_STATUS 0x05090002
> [...] repeated a hundred times with only the first line changing a bit [...]

Something in the mesa drivers is emitting a command buffer without a proper
virtual address for CB5.