linux-kernel - [tip:x86/mm] x86/mm: Do not flush last cacheline twice in clflush_cache

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Message-ID: <tip-6c434d6176c0cb42847c33245189667d645db7bf@git.kernel.org>
Date:	Mon, 11 May 2015 05:45:39 -0700
From:	tip-bot for Ross Zwisler <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	luto@...capital.net, linux-kernel@...r.kernel.org,
	brgerst@...il.com, bp@...en8.de, mcgrof@...e.com, bp@...e.de,
	toshi.kani@...com, hpa@...or.com, akpm@...ux-foundation.org,
	ross.zwisler@...ux.intel.com, tglx@...utronix.de,
	peterz@...radead.org, dvlasenk@...hat.com, mingo@...nel.org,
	torvalds@...ux-foundation.org
Subject: [tip:x86/mm] x86/mm:
  Do not flush last cacheline twice in clflush_cache_range()

Commit-ID:  6c434d6176c0cb42847c33245189667d645db7bf
Gitweb:     http://git.kernel.org/tip/6c434d6176c0cb42847c33245189667d645db7bf
Author:     Ross Zwisler <ross.zwisler@...ux.intel.com>
AuthorDate: Mon, 11 May 2015 10:15:49 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
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@...or.com>
Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@...e.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Toshi Kani <toshi.kani@...com>
Link: http://lkml.kernel.org/r/1430259192-18802-1-git-send-email-ross.zwisler@linux.intel.com
Link: http://lkml.kernel.org/r/1431332153-18566-5-git-send-email-bp@alien8.de
[ Changed it to 'void *' to simplify the type conversions. ]
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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();
 }
--
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