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authorChris Wilson <[email protected]>2012-07-15 12:34:22 +0100
committerDaniel Vetter <[email protected]>2012-07-25 10:39:57 +0200
commitd3373a241bbf034a1ef43e6417e3d0029c8a8145 (patch)
tree8e35bc0fb55b1ef69f53ed3f110fbaab4786b72e
parent79158103bf20c9ff55204ceb78a5773f422b03be (diff)
drm/i915: Flush the context object from the CPU caches upon switching
The issue is that we stale data in the CPU caches, when we come to swap-out the object, the CPU may short-circuit the reads from those cacheline and so corrupt the context object. Secondary, leaving the context object as being marked in the CPU write domain whilst on the GPU active list is a bad idea and will throw warnings later. Note: Thanks to calling set_to_gtt_domain with write = false and not setting any gpu write domain when putting a context object onto the active list (when we switch away from it) the set_to_gtt_domain call won't block. Signed-off-by: Chris Wilson <[email protected]> Reviewed-by: Ben Widawsky <[email protected]> [danvet: Added a note to the commit message and a comment in the code to explain the clever non-blocking trick.] Signed-off-by: Daniel Vetter <[email protected]>
-rw-r--r--drivers/gpu/drm/i915/i915_gem_context.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 18eee8d2522d..65639ad72808 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -374,6 +374,17 @@ static int do_switch(struct drm_i915_gem_object *from_obj,
if (ret)
return ret;
+ /* Clear this page out of any CPU caches for coherent swap-in/out. Note
+ * that thanks to write = false in this call and us not setting any gpu
+ * write domains when putting a context object onto the active list
+ * (when switching away from it), this won't block.
+ * XXX: We need a real interface to do this instead of trickery. */
+ ret = i915_gem_object_set_to_gtt_domain(to->obj, false);
+ if (ret) {
+ i915_gem_object_unpin(to->obj);
+ return ret;
+ }
+
if (!to->obj->has_global_gtt_mapping)
i915_gem_gtt_bind_object(to->obj, to->obj->cache_level);