(In reply to comment #12)
> I think these are actually several bugs at play here.
> 
> 1. CPU only has a 256 MB window into vram.  If the window is full due to
> fragmentation or other mapped buffers, we fail.  Does disabling hyperz help?
> set env var R600_HYPERZ=0 (mesa 9.1 or older), or R600_DEBUG=nohyperz (mesa
> git).
> 
> 2. running out of GPU accessible memory when migrating buffers.  Does
> setting radeon.gartsize=1024 on the kernel command line in grub help?

Just tried both, but nothing changed...