x86: Add support for Intel HWP feature detection.

Add support of Hardware Managed Performance States (HWP) described in Volume 3
section 14.4 of the SDM.

One bit CPUID.06H:EAX[bit 7] expresses the presence of the HWP feature on
the processor. The remaining bits CPUID.06H:EAX[bit 8-11] denote the
presense of various HWP features.

Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

arch/x86/include/asm/cpufeature.h

@@ -189,6 +189,11 @@
 #define X86_FEATURE_DTHERM	( 7*32+ 7) /* Digital Thermal Sensor */
 #define X86_FEATURE_HW_PSTATE	( 7*32+ 8) /* AMD HW-PState */
 #define X86_FEATURE_PROC_FEEDBACK ( 7*32+ 9) /* AMD ProcFeedbackInterface */
+#define X86_FEATURE_HWP		( 7*32+ 10) /* "hwp" Intel HWP */
+#define X86_FEATURE_HWP_NOITFY	( 7*32+ 11) /* Intel HWP_NOTIFY */
+#define X86_FEATURE_HWP_ACT_WINDOW ( 7*32+ 12) /* Intel HWP_ACT_WINDOW */
+#define X86_FEATURE_HWP_EPP	( 7*32+13) /* Intel HWP_EPP */
+#define X86_FEATURE_HWP_PKG_REQ ( 7*32+14) /* Intel HWP_PKG_REQ */
 
 /* Virtualization flags: Linux defined, word 8 */
 #define X86_FEATURE_TPR_SHADOW  ( 8*32+ 0) /* Intel TPR Shadow */

arch/x86/kernel/cpu/scattered.c

@@ -36,6 +36,11 @@ void init_scattered_cpuid_features(struct cpuinfo_x86 *c)
 		{ X86_FEATURE_ARAT,		CR_EAX, 2, 0x00000006, 0 },
 		{ X86_FEATURE_PLN,		CR_EAX, 4, 0x00000006, 0 },
 		{ X86_FEATURE_PTS,		CR_EAX, 6, 0x00000006, 0 },
+		{ X86_FEATURE_HWP,		CR_EAX, 7, 0x00000006, 0 },
+		{ X86_FEATURE_HWP_NOITFY,	CR_EAX, 8, 0x00000006, 0 },
+		{ X86_FEATURE_HWP_ACT_WINDOW,	CR_EAX, 9, 0x00000006, 0 },
+		{ X86_FEATURE_HWP_EPP,		CR_EAX,10, 0x00000006, 0 },
+		{ X86_FEATURE_HWP_PKG_REQ,	CR_EAX,11, 0x00000006, 0 },
 		{ X86_FEATURE_APERFMPERF,	CR_ECX, 0, 0x00000006, 0 },
 		{ X86_FEATURE_EPB,		CR_ECX, 3, 0x00000006, 0 },
 		{ X86_FEATURE_HW_PSTATE,	CR_EDX, 7, 0x80000007, 0 },