[tip:x86/mm] x86/mm: Do not flush last cacheline twice in clflush_cache_range()

[tip-bot for Ross Zwisler]

Commit-ID:  6c434d6176c0cb42847c33245189667d645db7bf
Gitweb:     http://git.kernel.org/tip/6c434d6176c0cb42847c33245189667d645db7bf
Author:     Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
AuthorDate: Mon, 11 May 2015 10:15:49 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 11 May 2015 10:38:44 +0200

x86/mm: Do not flush last cacheline twice in clflush_cache_range()

The current algorithm used in clflush_cache_range() can cause
the last cache line of the buffer to be flushed twice. Fix that
algorithm so that each cache line will only be flushed once.

Reported-by: H. Peter Anvin <hpa@xxxxxxxxx>
Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Luis R. Rodriguez <mcgrof@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxx>
Link: http://lkml.kernel.org/r/1430259192-18802-1-git-send-email-ross.zwisler@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1431332153-18566-5-git-send-email-bp@xxxxxxxxx
[ Changed it to 'void *' to simplify the type conversions. ]
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/mm/pageattr.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 89af288..5ddd900 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -129,16 +129,15 @@ within(unsigned long addr, unsigned long start, unsigned long end)
  */
 void clflush_cache_range(void *vaddr, unsigned int size)
 {
-	void *vend = vaddr + size - 1;
+	unsigned long clflush_mask = boot_cpu_data.x86_clflush_size - 1;
+	void *vend = vaddr + size;
+	void *p;
 
 	mb();
 
-	for (; vaddr < vend; vaddr += boot_cpu_data.x86_clflush_size)
-		clflushopt(vaddr);
-	/*
-	 * Flush any possible final partial cacheline:
-	 */
-	clflushopt(vend);
+	for (p = (void *)((unsigned long)vaddr & ~clflush_mask);
+	     p < vend; p += boot_cpu_data.x86_clflush_size)
+		clflushopt(p);
 
 	mb();
 }
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/