[Intel-gfx] [PATCH v2 3/3] drm/i915: Use page coloring to provide the guard page at the end of the GTT

[Chris Wilson]

On Mon, Feb 06, 2017 at 12:54:39PM +0000, Matthew Auld wrote:
> On 6 February 2017 at 08:45, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > As we now mark the reserved hole (drm_mm.head_node) with the special
> > UNEVICTABLE color, we can use the page coloring to avoid prefetching of
> > the CS beyond the end of the GTT.
> >
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> > @@ -3241,14 +3246,14 @@ int i915_ggtt_init_hw(struct drm_i915_private *dev_priv)
> >
> >         INIT_LIST_HEAD(&dev_priv->vm_list);
> >
> > -       /* Subtract the guard page before address space initialization to
> > -        * shrink the range used by drm_mm.
> > +       /* Note that we use page colouring to enforce a guard page at the
> > +        * end of the address space. This is required as the CS may prefetch
> > +        * beyond the end of the batch buffer, across the page boundary,
> > +        * and beyond the end of the GTT if we do provide a guard.
> if we do not provide a guard?
> 
> Reviewed-by: Matthew Auld <matthew.auld at intel.com>

Thanks for the review, and now back to the usual breaking of CI.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre