This should really have been added in BDW integration, as well as:
commit
93bd8649dba3155d1a0ba2a902d9c49f1c75a1da
Author: Ben Widawsky <ben@bwidawsk.net>
Date: Tue Jul 16 16:50:06 2013 -0700
drm/i915: Put the mm in the parent address space
It didn't really matter before, but it will in the future.
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>