Created attachment 91242 [details] [review]
possible fix

Does this fix the issue?  The issue is that that buffer is larger than the pci
bar window into vram.  The patch forces a scratch copy for all uploads.  It
would also probably be good to fix the kernel to check the offset in
radeon_mode_dumb_mmap() if the domain is vram to see if it's larger than the
pci window and return an error if so.