x86: Look for IA32_ENERGY_PERF_BIAS support

The new IA32_ENERGY_PERF_BIAS MSR allows system software to give
hardware a hint whether OS policy favors more power saving,
or more performance.  This allows the OS to have some influence
on internal hardware power/performance tradeoffs where the OS
has previously had no influence.

The support for this feature is indicated by CPUID.06H.ECX.bit3,
as documented in the Intel Architectures Software Developer's Manual.

This patch discovers support of this feature and displays it
as "epb" in /proc/cpuinfo.
Signed-off-by: NVenkatesh Pallipadi <venki@google.com>
LKML-Reference: <alpine.LFD.2.00.1006032310160.6669@localhost.localdomain>
Signed-off-by: NLen Brown <len.brown@intel.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/cpufeature.h

@@ -162,6 +162,7 @@
 #define X86_FEATURE_IDA		(7*32+ 0) /* Intel Dynamic Acceleration */
 #define X86_FEATURE_ARAT	(7*32+ 1) /* Always Running APIC Timer */
 #define X86_FEATURE_CPB		(7*32+ 2) /* AMD Core Performance Boost */
+#define X86_FEATURE_EPB		(7*32+ 3) /* IA32_ENERGY_PERF_BIAS support */
 
 /* Virtualization flags: Linux defined */
 #define X86_FEATURE_TPR_SHADOW  (8*32+ 0) /* Intel TPR Shadow */

arch/x86/include/asm/msr-index.h

@@ -238,6 +238,8 @@
 
 #define MSR_IA32_TEMPERATURE_TARGET	0x000001a2
 
+#define MSR_IA32_ENERGY_PERF_BIAS	0x000001b0
+
 /* MISC_ENABLE bits: architectural */
 #define MSR_IA32_MISC_ENABLE_FAST_STRING	(1ULL << 0)
 #define MSR_IA32_MISC_ENABLE_TCC		(1ULL << 1)

arch/x86/kernel/cpu/addon_cpuid_features.c

@@ -33,6 +33,7 @@ void __cpuinit init_scattered_cpuid_features(struct cpuinfo_x86 *c)
 		{ X86_FEATURE_IDA,   		CR_EAX, 1, 0x00000006 },
 		{ X86_FEATURE_ARAT,  		CR_EAX, 2, 0x00000006 },
 		{ X86_FEATURE_APERFMPERF,	CR_ECX, 0, 0x00000006 },
+		{ X86_FEATURE_EPB,		CR_ECX, 3, 0x00000006 },
 		{ X86_FEATURE_CPB,   		CR_EDX, 9, 0x80000007 },
 		{ X86_FEATURE_NPT,   		CR_EDX, 0, 0x8000000a },
 		{ X86_FEATURE_LBRV,  		CR_EDX, 1, 0x8000000a },