[PATCH] i386: i386 add Intel BTS cpufeature bit and detection (take 2)

Here is a small patch for i386 which adds a cpufeature flag and
detection code for Intel's Branch Trace Store (BTS) feature. This
feature can be found on Intel P4 and Core 2 processors among others.
It can also be used by perfmon.

changelog:
	- add CPU_FEATURE_BTS
	- add Branch Trace Store detection

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

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

2 files changed, 4 insertions, 0 deletions

diff --git a/arch/i386/kernel/cpu/intel.c b/arch/i386/kernel/cpu/intel.c
index 3ae795e9056d..56fe26584957 100644
--- a/arch/i386/kernel/cpu/intel.c
+++ b/arch/i386/kernel/cpu/intel.c
@@ -199,6 +199,8 @@ static void __cpuinit init_intel(struct cpuinfo_x86 *c)
         if (cpu_has_ds) {
                 unsigned int l1;
                 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 --git a/include/asm-i386/cpufeature.h b/include/asm-i386/cpufeature.h
index 4c83e059228f..3f92b94e0d75 100644
--- a/include/asm-i386/cpufeature.h
+++ b/include/asm-i386/cpufeature.h
@@ -74,6 +74,7 @@
 #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 */
@@ -138,6 +139,7 @@
 #define cpu_has_ds              boot_cpu_has(X86_FEATURE_DS)
 #define cpu_has_pebs            boot_cpu_has(X86_FEATURE_PEBS)
 #define cpu_has_clflush         boot_cpu_has(X86_FEATURE_CLFLSH)
+#define cpu_has_bts             boot_cpu_has(X86_FEATURE_BTS)
 
 #endif /* __ASM_I386_CPUFEATURE_H */