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[patch 58/76] x86: dont use P6_NOPs if compiling with CONFIG_X86_GENERIC

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From: Chris Wright <chrisw@...>
To: <linux-kernel@...>, <stable@...>
Cc: Justin Forbes <jmforbes@...>, Zwane Mwaikambo <zwane@...>, Theodore Ts'o <tytso@...>, Randy Dunlap <rdunlap@...>, Dave Jones <davej@...>, Chuck Wolber <chuckw@...>, Chris Wedgwood <reviews@...>, Michael Krufky <mkrufky@...>, Chuck Ebbert <cebbert@...>, Domenico Andreoli <cavokz@...>, <torvalds@...>, <akpm@...>, <alan@...>, H. Peter Anvin <hpa@...>, Ingo Molnar <mingo@...>, Thomas Gleixner <tglx@...>, Greg Kroah-Hartman <gregkh@...>
Subject: [patch 58/76] x86: dont use P6_NOPs if compiling with CONFIG_X86_GENERIC
Date: Friday, March 21, 2008 - 6:43 pm

-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: H. Peter Anvin <hpa@zytor.com>

x86: don't use P6_NOPs if compiling with CONFIG_X86_GENERIC

P6_NOPs are definitely not supported on some VIA CPUs, and possibly
(unverified) on AMD K7s.  It is also the only thing that prevents a
686 kernel from running on Transmeta TM3x00/5x00 (Crusoe) series.

The performance benefit over generic NOPs is very small, so when
building for generic consumption, avoid using them.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[cebbert@redhat.com: backport take 2, with parens this time]
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

 include/asm-x86/processor_32.h |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/include/asm-x86/processor_32.h
+++ b/include/asm-x86/processor_32.h
@@ -712,9 +712,10 @@ static inline unsigned int cpuid_edx(uns
 #define ASM_NOP6 K7_NOP6
 #define ASM_NOP7 K7_NOP7
 #define ASM_NOP8 K7_NOP8
-#elif defined(CONFIG_M686) || defined(CONFIG_MPENTIUMII) || \
+#elif (defined(CONFIG_M686) || defined(CONFIG_MPENTIUMII) || \
       defined(CONFIG_MPENTIUMIII) || defined(CONFIG_MPENTIUMM) || \
-      defined(CONFIG_MCORE2) || defined(CONFIG_PENTIUM4)
+      defined(CONFIG_MCORE2) || defined(CONFIG_PENTIUM4)) && \
+      !defined(CONFIG_X86_GENERIC)
 #define ASM_NOP1 P6_NOP1
 #define ASM_NOP2 P6_NOP2
 #define ASM_NOP3 P6_NOP3

-- 
--
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[patch 58/76] x86: dont use P6_NOPs if compiling with CONFIG..., Chris Wright, (Fri Mar 21, 6:43 pm)