x86: Use clflushopt in drm_clflush_page
If clflushopt is available on the system, use it instead of clflush in
drm_clflush_page.
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Link: http://lkml.kernel.org/r/1393441612-19729-4-git-send-email-ross.zwisler@linux.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c
index bb8f580..c518fb6 100644
--- a/drivers/gpu/drm/drm_cache.c
+++ b/drivers/gpu/drm/drm_cache.c
@@ -32,6 +32,12 @@
#include <drm/drmP.h>
#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.
+ */
static void
drm_clflush_page(struct page *page)
{
@@ -44,7 +50,7 @@
page_virtual = kmap_atomic(page);
for (i = 0; i < PAGE_SIZE; i += size)
- clflush(page_virtual + i);
+ clflushopt(page_virtual + i);
kunmap_atomic(page_virtual);
}