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

[Chris Wilson]

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.
> 
> Reported-by: Mike Lothian <mike at fireburn.co.uk>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96584
> Fixes: f7770bfd9fd2 ("drm/i915: Skip clearing the GGTT on full-ppgtt systems")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: David Weinehall <david.weinehall at intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

Ping?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre