[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>

2 files changed, 9 insertions, 0 deletions

diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index fc944b5e8f4a..619af2e2fa26 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/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);
diff --git a/include/asm-x86_64/cpufeature.h b/include/asm-x86_64/cpufeature.h
index 65eb39e8f3cc..d280384807ef 100644
--- a/include/asm-x86_64/cpufeature.h
+++ b/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 */