[PATCH] x86-64: x86-64 add Intel BTS cpufeature bit and detection (take 2)

Here is a small patch for x86-64 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: Nstephane eranian <eranian@hpl.hp.com>
Signed-off-by: NAndi Kleen <ak@suse.de>

arch/x86_64/kernel/setup.c

@@ -838,6 +838,8 @@ static void __cpuinit init_intel(struct cpuinfo_x86 *c)
 	if (cpu_has_ds) {
 		unsigned int l1, l2;
 		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);
 	}

include/asm-x86_64/cpufeature.h

@@ -69,6 +69,7 @@
 #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 */
+#define X86_FEATURE_BTS		(3*32+11) /* Branch Trace Store */
 
 /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
 #define X86_FEATURE_XMM3	(4*32+ 0) /* Streaming SIMD Extensions-3 */
@@ -115,5 +116,6 @@
 #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)
+#define cpu_has_bts 	       boot_cpu_has(X86_FEATURE_BTS)
 
 #endif /* __ASM_X8664_CPUFEATURE_H */