linux-kernel - [PATCH] i386 add Intel PEBS and BTS cpufeature bits and detection

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Date:	Wed, 15 Nov 2006 13:32:41 -0800
From:	Stephane Eranian <eranian@....hp.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...l.org, Stephane Eranian <eranian@....hp.com>
Subject: [PATCH] i386 add Intel PEBS and BTS cpufeature bits and detection

Hello,

Here is a small patch that adds two cpufeature bits to represent
Intel's Precise-Event-Based Sampling (PEBS) and Branch Trace Store
(BTS) features. Those features can be found on Intel P4 and Core 2 
processors among others and can be used by perfmon.

changelog:
	- add CPU_FEATURE_PEBS and CPU_FEATURE_BTS
	- add feature detection code

signed-off-by: stephane eranian <eranian@....hp.com>

diff --exclude=.git -urNp linux-2.6.orig/arch/i386/kernel/cpu/intel.c linux-2.6.base/arch/i386/kernel/cpu/intel.c
--- linux-2.6.orig/arch/i386/kernel/cpu/intel.c	2006-10-17 05:33:35.000000000 -0700
+++ linux-2.6.base/arch/i386/kernel/cpu/intel.c	2006-11-15 08:12:22.000000000 -0800
@@ -97,7 +97,7 @@ static int __cpuinit num_cpu_cores(struc
 
 static void __cpuinit init_intel(struct cpuinfo_x86 *c)
 {
-	unsigned int l2 = 0;
+	unsigned int l1, l2 = 0;
 	char *p = NULL;
 
 #ifdef CONFIG_X86_F00F_BUG
@@ -195,6 +195,14 @@ static void __cpuinit init_intel(struct 
 	if ((c->x86 == 0xf && c->x86_model >= 0x03) ||
 		(c->x86 == 0x6 && c->x86_model >= 0x0e))
 		set_bit(X86_FEATURE_CONSTANT_TSC, c->x86_capability);
+
+	if (cpu_has_ds) {
+		rdmsr(MSR_IA32_MISC_ENABLE, l1, l2);
+		if (!(l1 & (1<<11)))
+			set_bit(X86_FEATURE_BTS, c->x86_capability);
+		if (!(l1 & (1<<12)))
+			set_bit(X86_FEATURE_PEBS, c->x86_capability);
+	}
 }
 
diff --exclude=.git -urNp linux-2.6.orig/include/asm-i386/cpufeature.h linux-2.6.base/include/asm-i386/cpufeature.h
--- linux-2.6.orig/include/asm-i386/cpufeature.h	2006-10-17 05:33:40.000000000 -0700
+++ linux-2.6.base/include/asm-i386/cpufeature.h	2006-11-15 08:13:37.000000000 -0800
@@ -73,6 +73,8 @@
 #define X86_FEATURE_UP		(3*32+ 9) /* smp kernel running on up */
 #define X86_FEATURE_FXSAVE_LEAK (3*32+10) /* FXSAVE leaks FOP/FIP/FOP */
 #define X86_FEATURE_ARCH_PERFMON (3*32+11) /* Intel Architectural PerfMon */
+#define X86_FEATURE_PEBS	(3*32+12)  /* Precise-Event Based Sampling */
+#define X86_FEATURE_BTS		(3*32+13)  /* Branch Trace Store */
 
 /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
 #define X86_FEATURE_XMM3	(4*32+ 0) /* Streaming SIMD Extensions-3 */
@@ -134,6 +136,9 @@
 #define cpu_has_phe_enabled	boot_cpu_has(X86_FEATURE_PHE_EN)
 #define cpu_has_pmm		boot_cpu_has(X86_FEATURE_PMM)
 #define cpu_has_pmm_enabled	boot_cpu_has(X86_FEATURE_PMM_EN)
+#define cpu_has_ds 		boot_cpu_has(X86_FEATURE_DTES)
+#define cpu_has_pebs 		boot_cpu_has(X86_FEATURE_PEBS)
+#define cpu_has_bts		boot_cpu_has(X86_FEATURE_BTS)
 
 #endif /* __ASM_I386_CPUFEATURE_H */
 
-
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