[PATCH] x86-64: add X86_FEATURE_PEBS and detection

Here is a patch (used by perfmon2) to detect the presence of the
Precise Event Based Sampling (PEBS) feature for Intel 64-bit processors.
The patch also adds the cpu_has_pebs macro.

changelog:
	- adds X86_FEATURE_PEBS
	- adds cpu_has_pebs to test for X86_FEATURE_PEBS

Signed-off-by: stephane eranian <eranian@hpl.hp.com>
Signed-off-by: Andi Kleen <ak@suse.de>

arch/x86_64/kernel/setup.c

@@ -835,6 +835,13 @@ static void __cpuinit init_intel(struct cpuinfo_x86 *c)
 			set_bit(X86_FEATURE_ARCH_PERFMON, &c->x86_capability);
 	}
 
+	if (cpu_has_ds) {
+		unsigned int l1, l2;
+		rdmsr(MSR_IA32_MISC_ENABLE, l1, l2);
+		if (!(l1 & (1<<12)))
+			set_bit(X86_FEATURE_PEBS, c->x86_capability);
+	}
+
 	n = c->extended_cpuid_level;
 	if (n >= 0x80000008) {
 		unsigned eax = cpuid_eax(0x80000008);

include/asm-x86_64/cpufeature.h

@@ -68,6 +68,7 @@
 #define X86_FEATURE_FXSAVE_LEAK (3*32+7)  /* FIP/FOP/FDP leaks through FXSAVE */
 #define X86_FEATURE_UP		(3*32+8) /* SMP kernel running on UP */
 #define X86_FEATURE_ARCH_PERFMON (3*32+9) /* Intel Architectural PerfMon */
+#define X86_FEATURE_PEBS	(3*32+10) /* Precise-Event Based Sampling */
 
 /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
 #define X86_FEATURE_XMM3	(4*32+ 0) /* Streaming SIMD Extensions-3 */
@@ -113,5 +114,6 @@
 #define cpu_has_centaur_mcr    0
 #define cpu_has_clflush	       boot_cpu_has(X86_FEATURE_CLFLSH)
 #define cpu_has_ds 	       boot_cpu_has(X86_FEATURE_DS)
+#define cpu_has_pebs 	       boot_cpu_has(X86_FEATURE_PEBS)
 
 #endif /* __ASM_X8664_CPUFEATURE_H */