linux-kernel - [PATCH] [7/8] CPA: Don't flush caches on CPUs that support self-snoop

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Message-Id: <20080211095022.7B8C31B41CE@basil.firstfloor.org>
Date:	Mon, 11 Feb 2008 10:50:22 +0100 (CET)
From:	Andi Kleen <ak@...e.de>
To:	tglx@...utronix.de, mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: [PATCH] [7/8] CPA: Don't flush caches on CPUs that support self-snoop


[2.6.25 candidate I believe]

The specification of SS in the public manuals is a little unclear,
but I got confirmation from Intel that SS implies that there is no cache
flush needed on caching attribute changes.

Signed-off-by: Andi Kleen <ak@...e.de>

---
 arch/x86/mm/pageattr.c       |    5 ++++-
 include/asm-x86/cpufeature.h |    1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

Index: linux/arch/x86/mm/pageattr.c
===================================================================
--- linux.orig/arch/x86/mm/pageattr.c
+++ linux/arch/x86/mm/pageattr.c
@@ -74,7 +74,7 @@ static void __cpa_flush_all(void *arg)
 	 */
 	__flush_tlb_all();
 
-	if (cache && boot_cpu_data.x86_model >= 4)
+	if (!cpu_has_ss && cache && boot_cpu_data.x86_model >= 4)
 		wbinvd();
 }
 
@@ -108,6 +108,9 @@ static void cpa_flush_range(unsigned lon
 	if (!cache)
 		return;
 
+	if (cpu_has_ss)
+		return;
+
 	/*
 	 * We only need to flush on one CPU,
 	 * clflush is a MESI-coherent instruction that
Index: linux/include/asm-x86/cpufeature.h
===================================================================
--- linux.orig/include/asm-x86/cpufeature.h
+++ linux/include/asm-x86/cpufeature.h
@@ -157,6 +157,7 @@ extern const char * const x86_power_flag
 #define cpu_has_mtrr		boot_cpu_has(X86_FEATURE_MTRR)
 #define cpu_has_mmx		boot_cpu_has(X86_FEATURE_MMX)
 #define cpu_has_fxsr		boot_cpu_has(X86_FEATURE_FXSR)
+#define cpu_has_ss		boot_cpu_has(X86_FEATURE_SELFSNOOP)
 #define cpu_has_xmm		boot_cpu_has(X86_FEATURE_XMM)
 #define cpu_has_xmm2		boot_cpu_has(X86_FEATURE_XMM2)
 #define cpu_has_xmm3		boot_cpu_has(X86_FEATURE_XMM3)
--
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