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Commit 3a32497f authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915/selftests: Provide full mb() around clflush 



clflush is an unserialised instruction and the IA manual strongly advises
you to serialise it with a mb. To be cautious, apply one before and one
after, so that it is serialised with both writes and reads without
worrying too much about the required direction.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarRodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180706174926.4712-1-chris@chris-wilson.co.uk
parent 8b293eb5

drivers/gpu/drm/i915/selftests/i915_gem_coherency.c

+18 −3
Original line number Diff line number Diff line
@@ -42,11 +42,21 @@ static int cpu_set(struct drm_i915_gem_object *obj, 


	page = i915_gem_object_get_page(obj, offset >> PAGE_SHIFT);

	map = kmap_atomic(page);

	if (needs_clflush & CLFLUSH_BEFORE)



	if (needs_clflush & CLFLUSH_BEFORE) {

		mb();

		clflush(map+offset_in_page(offset) / sizeof(*map));

		mb();

	}



	map[offset_in_page(offset) / sizeof(*map)] = v;

	if (needs_clflush & CLFLUSH_AFTER)



	if (needs_clflush & CLFLUSH_AFTER) {

		mb();

		clflush(map+offset_in_page(offset) / sizeof(*map));

		mb();

	}



	kunmap_atomic(map);



	i915_gem_obj_finish_shmem_access(obj);
@@ -68,8 +78,13 @@ static int cpu_get(struct drm_i915_gem_object *obj, 


	page = i915_gem_object_get_page(obj, offset >> PAGE_SHIFT);

	map = kmap_atomic(page);

	if (needs_clflush & CLFLUSH_BEFORE)



	if (needs_clflush & CLFLUSH_BEFORE) {

		mb();

		clflush(map+offset_in_page(offset) / sizeof(*map));

		mb();

	}



	*v = map[offset_in_page(offset) / sizeof(*map)];

	kunmap_atomic(map);