On Mon, Nov 07, 2016 at 03:46:28PM +0000, Chris Wilson wrote:
> On LLC, or even snooped, machines rendering via the GPU ends up in the CPU
> cache. This cacheline dirt also needs to be flushed to main memory when
> moving to an incoherent domain, such as the display's scanout engine.
> Mostly, this happens because either the object is marked as dirty from
> its first use or is avoided by setting the object into the display
> domain from the start.
>
> Fixes: 0f71979ab7fb ("drm/i915: Performed deferred clflush inside set-cache-level")
> References: https://bugs.freedesktop.org/show_bug.cgi?id=95414
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.0+
> ---
> drivers/gpu/drm/i915/i915_gem_execbuffer.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index 30f6eb516ca3..30b684fecf09 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -1282,6 +1282,7 @@ void i915_vma_move_to_active(struct i915_vma *vma,
>
> /* update for the implicit flush after a batch */
> obj->base.write_domain &= ~I915_GEM_GPU_DOMAINS;
> + obj->cache_dirty |= obj->cache_level != I915_CACHE_NONE;
I915_CACHE_WT shouldn't dirty the cache either, so could be excluded
as well.
Everything else makes sense
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> }
>
> if (flags & EXEC_OBJECT_NEEDS_FENCE)
> --
> 2.10.2
--
Ville Syrjälä
Intel OTC
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