linux-kernel - [PATCH 5/6] x86: Use clwb in drm_clflush

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Date:	Tue, 11 Nov 2014 11:43:15 -0700
From:	Ross Zwisler <ross.zwisler@...ux.intel.com>
To:	linux-kernel@...r.kernel.org
Cc:	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	H Peter Anvin <h.peter.anvin@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org, x86@...nel.org
Subject: [PATCH 5/6] x86: Use clwb in drm_clflush_page

If clwb is available on the system, use it in drm_clflush_page.
If clwb is not available, fall back to clflushopt if you can.
If clflushopt is not supported, fall all the way back to clflush.

Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc: H Peter Anvin <h.peter.anvin@...el.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: David Airlie <airlied@...ux.ie>
Cc: dri-devel@...ts.freedesktop.org
Cc: x86@...nel.org
---
 drivers/gpu/drm/drm_cache.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c
index a6b6906..aad9d82 100644
--- a/drivers/gpu/drm/drm_cache.c
+++ b/drivers/gpu/drm/drm_cache.c
@@ -34,9 +34,9 @@
 #if defined(CONFIG_X86)
 
 /*
- * clflushopt is an unordered instruction which needs fencing with mfence or
- * sfence to avoid ordering issues.  For drm_clflush_page this fencing happens
- * in the caller.
+ * clwb and clflushopt are unordered instructions which need fencing with
+ * mfence or sfence to avoid ordering issues.  For drm_clflush_page this
+ * fencing happens in the caller.
  */
 static void
 drm_clflush_page(struct page *page)
@@ -50,7 +50,7 @@ drm_clflush_page(struct page *page)
 
 	page_virtual = kmap_atomic(page);
 	for (i = 0; i < PAGE_SIZE; i += size)
-		clflushopt(page_virtual + i);
+		clwb(page_virtual + i);
 	kunmap_atomic(page_virtual);
 }
 
-- 
1.9.3

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