R9 285 tonga, git llvm, drm-next-4.9-wip.

Since Mesa commit -

commit ffa1c669ddb48c25bab3457b8b2bfcd255acc674
Author: Nicolai Hähnle <nicolai.haehnle@amd.com>
Date:   Wed Sep 7 10:50:59 2016 +0200

    winsys/amdgpu: enable buffer allocation from slabs

Using VCE encode fails (but not instantly) with 

[drm:amdgpu_vce_cs_reloc [amdgpu]] *ERROR* BO to small for addr 0x010005fe00
139 138

If you have gstreamer + vce you may be able to reproduce with -

gst-launch-1.0 -f ximagesrc use-damage=0 startx=0 starty=0 endx=1919 endy=1079
! queue ! videoconvert ! video/x-raw,framerate=60/1,format=NV12  ! queue !
vaapih264enc ! video/x-h264,profile=baseline ! fakesink

Which will run forever, it takes a few seconds to trigger for me. It assumes
your screen is 1080p so may need tweaking and I guess may luck out of
triggering at smaller sizes.

Other tests not involving gstreamer/screen grabbing = avconv reading 1080p
rawvid from tmpfs are also affected.