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From: "Michael S. Tsirkin" <mst@redhat.com>
To: linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	the arch/x86 maintainers <x86@kernel.org>,
	Davidlohr Bueso <dbueso@suse.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	virtualization <virtualization@lists.linux-foundation.org>,
	Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
	Arnd Bergmann <arnd@arndb.de>, Andy Lutomirski <luto@kernel.org>,
	Andrey Konovalov <andreyknvl@google.com>,
	Borislav Petkov <bp@suse.de>
Subject: [PATCH v3 3/4] x86: tweak the comment about use of wmb for IO
Date: Wed, 13 Jan 2016 22:12:39 +0200	[thread overview]
Message-ID: <1452715911-12067-4-git-send-email-mst@redhat.com> (raw)
In-Reply-To: <1452715911-12067-1-git-send-email-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 as historial unless somebody can point to a case where
they care about the performance, but tweak the comment so people
don't think they are strictly required in all cases.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 arch/x86/include/asm/barrier.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index a291745..bfb28ca 100644
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -6,7 +6,7 @@
 
 /*
  * Force strict CPU ordering.
- * And yes, this is required on UP too when we're talking
+ * And yes, this might be required on UP too when we're talking
  * to devices.
  */
 
-- 
MST

  parent reply	other threads:[~2016-01-13 20:12 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-13 20:12 [PATCH v3 0/4] x86: faster mb()+documentation tweaks Michael S. Tsirkin
2016-01-13 20:12 ` [PATCH v3 1/4] x86: add cc clobber for addl Michael S. Tsirkin
2016-01-13 20:12 ` Michael S. Tsirkin
2016-01-13 20:12 ` [PATCH v3 2/4] x86: drop a comment left over from X86_OOSTORE Michael S. Tsirkin
2016-01-13 20:12   ` Michael S. Tsirkin
2016-01-13 20:12 ` [PATCH v3 3/4] x86: tweak the comment about use of wmb for IO Michael S. Tsirkin
2016-01-13 20:12 ` Michael S. Tsirkin [this message]
2016-01-13 20:12 ` [PATCH v3 4/4] x86: drop mfence in favor of lock+addl Michael S. Tsirkin
2016-01-13 20:12 ` Michael S. Tsirkin
2016-01-14 11:39 ` [PATCH v3 0/4] x86: faster mb()+documentation tweaks Borislav Petkov
2016-01-14 11:39   ` Borislav Petkov
2016-01-26  8:23   ` Michael S. Tsirkin
2016-01-26  8:23     ` Michael S. Tsirkin
2016-01-26  8:26     ` Boris Petkov
2016-01-26  8:26       ` Boris Petkov

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