[Intel-gfx] [PATCH 1/5] agp/intel: Serialise after GTT updates

[Chris Wilson]

On Fri, Feb 13, 2015 at 10:59:42AM +0200, Ville Syrjälä wrote:
> Hmm, except we don't do it for clear_range(), but I guess that's not a
> huge issue, just means someone could clobber some other memory besides
> the scratch page if accidentally writing to a cleared area of the ggtt.

It's a very small hole, only since it is the ggtt the only user is the
kernel. (Except for i915.enable_ppgtt=0.) It is possible to forgo that
clear entirely (looks at the PD implementation for a current violator,
and that is a good example for where the extra WC writes can be have 
easurable impact on synmark).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre