[Intel-gfx] [PATCH] drm/i915: Fill unused GGTT with scratch pages for VT-d

[Chris Wilson]

On Fri, Jul 08, 2016 at 03:29:30PM +0300, David Weinehall wrote:
> On Fri, Jun 24, 2016 at 02:07:14PM +0100, Chris Wilson wrote:
> > One of the numerous VT-d workarounds we require is that the display
> > hardware reads past the end of the buffer triggering VT-d faults. This
> > is acknowledged in the code as being safe "since we fill the unused
> > portions of the GGTT with the scratch page". Alas, that is no longer
> > always true and so we trigger DMAR read faults.
> > 
> > Skylake also requires another workaround to avoid mixing VT-d and
> > unpopulated PTE, and so there we also need to ensure we fill unused
> > entries with the scratch page.
> 
> LGTM.
> 
> Reviewed-by: David Weinehall <david.weinehall at linux.intel.com>

Ta,
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre