[PATCH v7 2/7] x86/cpu, kvm: Add the NO_NESTED_DATA_BP feature

[Kim Phillips]

The "Processor ignores nested data breakpoints" feature was being
open-coded for KVM in __do_cpuid_func().  Add it to its newly added
CPUID leaf 0x80000021 EAX proper, and propagate it in kvm_set_cpu_caps()
instead.

Also drop the bit description comments now it's more self-describing.

Signed-off-by: Kim Phillips <kim.phillips@xxxxxxx>
---
 arch/x86/include/asm/cpufeatures.h | 3 +++
 arch/x86/kvm/cpuid.c               | 8 ++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index a84536876794..8255b95a7987 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -428,6 +428,9 @@
 #define X86_FEATURE_V_TSC_AUX		(19*32+ 9) /* "" Virtual TSC_AUX */
 #define X86_FEATURE_SME_COHERENT	(19*32+10) /* "" AMD hardware-enforced cache coherency */
 
+/* AMD-defined Extended Feature 2 EAX, CPUID level 0x80000021 (EAX), word 20 */
+#define X86_FEATURE_NO_NESTED_DATA_BP	(20*32+ 0) /* "" AMD No Nested Data Breakpoints */
+
 /*
  * BUG word(s)
  */
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 596061c1610e..c9081e3a1b66 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -741,6 +741,10 @@ void kvm_set_cpu_caps(void)
 		0 /* SME */ | F(SEV) | 0 /* VM_PAGE_FLUSH */ | F(SEV_ES) |
 		F(SME_COHERENT));
 
+	kvm_cpu_cap_mask(CPUID_8000_0021_EAX,
+		F(NO_NESTED_DATA_BP)
+	);
+
 	kvm_cpu_cap_mask(CPUID_C000_0001_EDX,
 		F(XSTORE) | F(XSTORE_EN) | F(XCRYPT) | F(XCRYPT_EN) |
 		F(ACE2) | F(ACE2_EN) | F(PHE) | F(PHE_EN) |
@@ -1222,9 +1226,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		break;
 	case 0x80000021:
 		entry->ebx = entry->ecx = entry->edx = 0;
+		cpuid_entry_override(entry, CPUID_8000_0021_EAX);
 		/*
 		 * Pass down these bits:
-		 *    EAX      0      NNDBP, Processor ignores nested data breakpoints
 		 *    EAX      2      LAS, LFENCE always serializing
 		 *    EAX      6      NSCB, Null selector clear base
 		 *
@@ -1235,7 +1239,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		 * KVM doesn't support SMM_CTL.
 		 *   EAX       9     SMM_CTL MSR is not supported
 		 */
-		entry->eax &= BIT(0) | BIT(2) | BIT(6);
+		entry->eax &= BIT(2) | BIT(6);
 		entry->eax |= BIT(9);
 		if (static_cpu_has(X86_FEATURE_LFENCE_RDTSC))
 			entry->eax |= BIT(2);
-- 
2.34.1