From d3373a241bbf034a1ef43e6417e3d0029c8a8145 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Sun, 15 Jul 2012 12:34:22 +0100 Subject: [PATCH] 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 Reviewed-by: Ben Widawsky [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 --- drivers/gpu/drm/i915/i915_gem_context.c | 11 +++++++++++ 1 file changed, 11 insertions(+) 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); -- 2.20.1