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[PATCH 03/10] x86/asm: Tweak the comment about wmb() use for IO

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From: "Michael S. Tsirkin" <mst@redhat.com>

On x86, we *do* still use the non-nop rmb()/wmb() for IO barriers, but
even that is generally questionable.

Leave them around for historical reasons, unless somebody can point to a
case where they care about the performance. Tweak the comment so people
don't think they are strictly required in all cases.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization <virtualization@lists.linux-foundation.org>
Link: http://lkml.kernel.org/r/1452715911-12067-4-git-send-email-mst@redhat.com
Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/include/asm/barrier.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index d2aa66a3a4b5..4f95b2affd88 100644
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -6,8 +6,8 @@
 
 /*
  * Force strict CPU ordering.
- * And yes, this is required on UP too when we're talking
- * to devices.
+ *
+ * And yes, this might be required on UP too when we're talking to devices.
  */
 
 #ifdef CONFIG_X86_32
-- 
2.3.5

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[PATCH 00/10] tip-queue 2016-01-26, rest Borislav Petkov <bp@alien8.de> - 2016-01-26 22:20 +0100
  [PATCH 09/10] x86/vdso: Use static_cpu_has() Borislav Petkov <bp@alien8.de> - 2016-01-26 22:20 +0100
  [PATCH 03/10] x86/asm: Tweak the comment about wmb() use for IO Borislav Petkov <bp@alien8.de> - 2016-01-26 22:20 +0100
  [PATCH 07/10] x86/alternatives: Add an auxilary section Borislav Petkov <bp@alien8.de> - 2016-01-26 22:20 +0100
  [PATCH 01/10] x86/asm: Add condition codes clobber to memory barrier macros Borislav Petkov <bp@alien8.de> - 2016-01-26 22:20 +0100
  [PATCH 06/10] x86/cpufeature: Get rid of the non-asm goto variant Borislav Petkov <bp@alien8.de> - 2016-01-26 22:20 +0100
    Re: [PATCH 06/10] x86/cpufeature: Get rid of the non-asm goto variant Brian Gerst <brgerst@gmail.com> - 2016-01-27 04:40 +0100
      [PATCH -v1.1 8/10] x86/alternatives: Discard dynamic check after init Borislav Petkov <bp@alien8.de> - 2016-01-27 09:50 +0100
      Re: [PATCH 06/10] x86/cpufeature: Get rid of the non-asm goto variant Borislav Petkov <bp@alien8.de> - 2016-01-27 09:50 +0100
        [PATCH -v1.1 06/10] x86/cpufeature: Get rid of the non-asm goto  variant Borislav Petkov <bp@alien8.de> - 2016-01-27 09:50 +0100

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