(In reply to Christian König from comment #19)
> > We are using kernel 4.0.3
> 
> Strange, that kernel should work perfectly fine.

I suspect the problem of that Tahiti user might not be directly related to the
patch. Or maybe he's experiencing the problematic aspects of unmapping the VA
range for all GEM handles...

(In reply to Christian König from comment #18)
> I'm working on that problem for years now, tracking VA ranges per GEM handle
> isn't really doable either (e.g. without breaking backward compatibility).

How would it break backwards compatibility? I'm not sure how not tracking the
VA ranges per GEM handle could ever work as expected with several GEM handles
referencing the same BO.

Anyway, if you think the Mesa patch is the best we can do for now, there would
at least need to be a way for userspace to know it's safe to unmap the VA
range, e.g. an info query.