[RFC PATCH 3/4] x86/cpufeatures: Add Page modification logging

[Nikunj A Dadhania <nikunj@amd.com>]

Page modification logging(PML) is a hardware feature designed to track
guest modified memory pages. PML enables the hypervisor to identify which
pages in a guest's memory have been changed since the last checkpoint or
during live migration.

The PML feature is advertised via CPUID leaf 0x8000000A ECX[4] bit.

Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
---
 arch/x86/include/asm/cpufeatures.h | 1 +
 arch/x86/kernel/cpu/scattered.c    | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 286d509f9363..069c0e17113a 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -227,6 +227,7 @@
 #define X86_FEATURE_PVUNLOCK		( 8*32+20) /* PV unlock function */
 #define X86_FEATURE_VCPUPREEMPT		( 8*32+21) /* PV vcpu_is_preempted function */
 #define X86_FEATURE_TDX_GUEST		( 8*32+22) /* "tdx_guest" Intel Trust Domain Extensions Guest */
+#define X86_FEATURE_PML			( 8*32+23) /* AMD Page Modification logging */
 
 /* Intel-defined CPU features, CPUID level 0x00000007:0 (EBX), word 9 */
 #define X86_FEATURE_FSGSBASE		( 9*32+ 0) /* "fsgsbase" RDFSBASE, WRFSBASE, RDGSBASE, WRGSBASE instructions*/
diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index b4a1f6732a3a..02fc16b28bc9 100644
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -48,6 +48,7 @@ static const struct cpuid_bit cpuid_bits[] = {
 	{ X86_FEATURE_PROC_FEEDBACK,		CPUID_EDX, 11, 0x80000007, 0 },
 	{ X86_FEATURE_AMD_FAST_CPPC,		CPUID_EDX, 15, 0x80000007, 0 },
 	{ X86_FEATURE_MBA,			CPUID_EBX,  6, 0x80000008, 0 },
+	{ X86_FEATURE_PML,			CPUID_ECX,  4, 0x8000000A, 0 },
 	{ X86_FEATURE_SMBA,			CPUID_EBX,  2, 0x80000020, 0 },
 	{ X86_FEATURE_BMEC,			CPUID_EBX,  3, 0x80000020, 0 },
 	{ X86_FEATURE_TSA_SQ_NO,		CPUID_ECX,  1, 0x80000021, 0 },
-- 
2.43.0