[PATCH 4/4] drm/i915: Flush stale cachelines on set-cache-level

[Chris Wilson <chris@chris-wilson.co.uk>]

Ensure that we flush any cache dirt out to main memory before the user
changes the cache-level as they may elect to bypass the cache (even after
declaring their access cache-coherent) via use of unprivileged MOCS.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: stable@vger.kernel.org
---
 drivers/gpu/drm/i915/gem/i915_gem_domain.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_domain.c b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
index 2e3ce2a69653..5d41e769a428 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_domain.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
@@ -277,6 +277,11 @@ int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj,
 
 	list_for_each_entry(vma, &obj->vma.list, obj_link)
 		vma->node.color = cache_level;
+
+	/* Flush any previous cache dirt in case of cache bypass */
+	if (obj->cache_dirty & ~obj->cache_coherent)
+		i915_gem_clflush_object(obj, I915_CLFLUSH_SYNC);
+
 	i915_gem_object_set_cache_coherency(obj, cache_level);
 	obj->cache_dirty = true; /* Always invalidate stale cachelines */
 
-- 
2.22.0