[Intel-gfx] [PATCH 1/2] drm/i915: Disallow pin ioctl completely for kms drivers

[Chris Wilson]

On Mon, Nov 24, 2014 at 11:30:24AM +0100, Daniel Vetter wrote:
> The problem here is that SNA pins batchbuffers to etch out a bit more
> performance. Iirc it started out as a w/a for i830M (which we've
> implemented in the kernel since a long time already).

Hmm, we only finally fixed it in the kernel a couple of months ago.

> The problem is
> that the pin ioctl wasn't added in
> 
> commit d23db88c3ab233daed18709e3a24d6c95344117f
> Author: Chris Wilson <chris at chris-wilson.co.uk>
> Date:   Fri May 23 08:48:08 2014 +0200
> 
>     drm/i915: Prevent negative relocation deltas from wrapping
> 
> Fix this by simply disallowing pinning from userspace so that the
> kernel is in full control of batch placement again. Especially since
> distros are moving towards running X as non-root, so most users won't
> even be able to see any benefits.

Pinning is a useful tool and it would also be useful to have again on
gen6+.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre