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). The problem is
that the pin ioctl wasn't added in
commit d23db88c3a
Author: Chris Wilson <chris@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.
UMS support is dead now, but we need this minimal patch for
backporting. Follow-up patch will remove the pin ioctl code
completely.
Note to backporters: You must have both
commit b45305fce5
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Mon Dec 17 16:21:27 2012 +0100
drm/i915: Implement workaround for broken CS tlb on i830/845
which laned in 3.8 and
commit c4d69da167
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon Sep 8 14:25:41 2014 +0100
drm/i915: Evict CS TLBs between batches
which is also marked cc: stable. Otherwise this could introduce a
regression by disabling the userspace w/a without the kernel w/a being
fully functional on i830/45.
References: https://bugs.freedesktop.org/show_bug.cgi?id=76554#c116
Cc: stable@vger.kernel.org # requires c4d69da167 and v3.8
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
d472fcc837