x86/cpufeatures: Add AMD FAST CPPC feature flag

Some AMD Zen 4 processors support a new feature FAST CPPC which allows for a faster CPPC loop due to internal architectural enhancements. The goal of this faster loop is higher performance at the same power consumption. Reference: See the page 99 of PPR for AMD Family 19h Model 61h rev.B1, docID 56713 Signed-off-by: Perry Yuan <perry.yuan@amd.com> Signed-off-by: Xiaojian Du <Xiaojian.Du@amd.com> Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
mariux64 · Jun 11, 2024 · c710775 · c710775
1 parent 83a7eef
commit c710775
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diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
@@ -470,6 +470,7 @@
 #define X86_FEATURE_BHI_CTRL		(21*32+ 2) /* "" BHI_DIS_S HW control available */
 #define X86_FEATURE_CLEAR_BHB_HW	(21*32+ 3) /* "" BHI_DIS_S HW control enabled */
 #define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* "" Clear branch history at vmexit using SW loop */
+#define X86_FEATURE_FAST_CPPC		(21*32 + 5) /* "" AMD Fast CPPC */
 
 /*
  * BUG word(s)

diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
@@ -45,6 +45,7 @@ static const struct cpuid_bit cpuid_bits[] = {
 	{ X86_FEATURE_HW_PSTATE,	CPUID_EDX,  7, 0x80000007, 0 },
 	{ X86_FEATURE_CPB,		CPUID_EDX,  9, 0x80000007, 0 },
 	{ X86_FEATURE_PROC_FEEDBACK,    CPUID_EDX, 11, 0x80000007, 0 },
+	{ X86_FEATURE_FAST_CPPC, 	CPUID_EDX, 15, 0x80000007, 0 },
 	{ X86_FEATURE_MBA,		CPUID_EBX,  6, 0x80000008, 0 },
 	{ X86_FEATURE_SMBA,		CPUID_EBX,  2, 0x80000020, 0 },
 	{ X86_FEATURE_BMEC,		CPUID_EBX,  3, 0x80000020, 0 },