[Intel-gfx] Patch "drm/i915: Don't use stolen memory for ring buffers with LLC" has been added to the 5.4-stable tree

[gregkh at linuxfoundation.org]

This is a note to let you know that I've just added the patch titled

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

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-i915-don-t-use-stolen-memory-for-ring-buffers-with-llc.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable at vger.kernel.org> know about it.


>From 690e0ec8e63da9a29b39fedc6ed5da09c7c82651 Mon Sep 17 00:00:00 2001
From: John Harrison <John.C.Harrison at Intel.com>
Date: Wed, 15 Feb 2023 17:11:00 -0800
Subject: drm/i915: Don't use stolen memory for ring buffers with LLC
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: John Harrison <John.C.Harrison at Intel.com>

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 at Intel.com>
Fixes: c58b735fc762 ("drm/i915: Allocate rings from stolen")
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
Cc: intel-gfx at lists.freedesktop.org
Cc: <stable at vger.kernel.org> # v4.9+
Tested-by: Jouni Högander <jouni.hogander at intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at 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 at intel.com>
Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 drivers/gpu/drm/i915/gt/intel_ringbuffer.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- 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_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))


Patches currently in stable-queue which might be from John.C.Harrison at Intel.com are

queue-5.4/drm-i915-don-t-use-stolen-memory-for-ring-buffers-with-llc.patch