drm/i915: Don't use stolen memory for ring buffers with LLC

commit 690e0ec8e63da9a29b39fedc6ed5da09c7c82651 upstream.

Direction from hardware is that stolen memory should never be used for
ring buffer allocations on platforms with LLC. There are too many
caching pitfalls due to the way stolen memory accesses are routed. So
it is safest to just not use it.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Fixes: c2b86cf5b66b ("drm/i915: Allocate rings from stolen")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v4.9+
Tested-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230216011101.1909009-2-John.C.Harrison@Intel.com
(cherry picked from commit f54c1f6c697c4297f7ed94283c184acc338a5cf8)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
index 808269b2108fbe40603e183dafc6acfafcd5e2ca..125f7bb67bee901eb49b326fe62b295ec99d5df1 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
@@ -1268,10 +1268,11 @@ static struct i915_vma *create_ring_vma(struct i915_ggtt *ggtt, int size)
 {
        struct i915_address_space *vm = &ggtt->vm;
        struct drm_i915_private *i915 = vm->i915;
-       struct drm_i915_gem_object *obj;
+       struct drm_i915_gem_object *obj = NULL;
        struct i915_vma *vma;
 
-       obj = i915_gem_object_create_stolen(i915, size);
+       if (!HAS_LLC(i915))
+               obj = i915_gem_object_create_stolen(i915, size);
        if (!obj)
                obj = i915_gem_object_create_internal(i915, size);
        if (IS_ERR(obj))