[PATCH v3 05/12] drm/ttm: Expose ttm_tt_unpopulate for driver use

[Michel Dänzer]

On 2020-11-25 1:57 p.m., Christian König wrote:
> 
> Well thinking more about this, it seems to be a another really good 
> argument why mapping pages from DMA-bufs into application address space 
> directly is a very bad idea :)

Apologies for going off on a tangent here...

Since allowing userspace mmap with dma-buf fds seems to be a trap in 
general[0], I wonder if there's any way we could stop supporting that?


[0] E.g. mutter had to disable handing out dma-bufs for screen capture 
by default with non-i915 for now, because in particular with discrete 
GPUs, direct CPU reads can be unusably slow (think single-digit frames 
per second), and of course there's other userspace which goes "ooh, 
dma-buf, let's map and read!".


-- 
Earthling Michel Dänzer               |               https://redhat.com
Libre software enthusiast             |             Mesa and X developer