If clwb is available on the system, use it in clflush_cache_range.
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.zwis...@linux.intel.com>
Cc: H Peter Anvin <h.peter.an...@intel.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: David Airlie <airl...@linux.ie>
Cc: dri-de...@lists.freedesktop.org
Cc: x...@kernel.org
---
 arch/x86/mm/pageattr.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 36de293..5229d45 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -126,8 +126,8 @@ within(unsigned long addr, unsigned long start, unsigned 
long end)
  * @vaddr:     virtual start address
  * @size:      number of bytes to flush
  *
- * clflushopt is an unordered instruction which needs fencing with mfence or
- * sfence to avoid ordering issues.
+ * clflushopt and clwb are unordered instructions which need fencing with
+ * mfence or sfence to avoid ordering issues.
  */
 void clflush_cache_range(void *vaddr, unsigned int size)
 {
@@ -136,11 +136,11 @@ void clflush_cache_range(void *vaddr, unsigned int size)
        mb();
 
        for (; vaddr < vend; vaddr += boot_cpu_data.x86_clflush_size)
-               clflushopt(vaddr);
+               clwb(vaddr);
        /*
         * Flush any possible final partial cacheline:
         */
-       clflushopt(vend);
+       clwb(vend);
 
        mb();
 }
-- 
1.9.3

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