[PATCH 3/5] KVM: x86: add support for CPUID leaf 0x80000021

[Borislav Petkov <bp@kernel.org>]

From: Paolo Bonzini <pbonzini@redhat.com>

Commit 58b3d12c0a860cda34ed9d2378078ea5134e6812 upstream.

CPUID leaf 0x80000021 defines some features (or lack of bugs) of AMD
processors.  Expose the ones that make sense via KVM_GET_SUPPORTED_CPUID.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/kvm/cpuid.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 8b07e48612d7..8ec86d2c1a41 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -810,7 +810,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		entry->edx = 0;
 		break;
 	case 0x80000000:
-		entry->eax = min(entry->eax, 0x8000001f);
+		entry->eax = min(entry->eax, 0x80000021);
 		break;
 	case 0x80000001:
 		entry->ebx &= ~GENMASK(27, 16);
@@ -875,6 +875,23 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		if (!boot_cpu_has(X86_FEATURE_SEV))
 			entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
 		break;
+	case 0x80000020:
+		entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
+		break;
+	case 0x80000021:
+		entry->ebx = entry->ecx = entry->edx = 0;
+		/*
+		 * 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
+		 *
+		 * Other defined bits are for MSRs that KVM does not expose:
+		 *   EAX      3      SPCL, SMM page configuration lock
+		 *   EAX      13     PCMSR, Prefetch control MSR
+		 */
+		entry->eax &= BIT(0) | BIT(2) | BIT(6);
+		break;
 	/*Add support for Centaur's CPUID instruction*/
 	case 0xC0000000:
 		/*Just support up to 0xC0000004 now*/
-- 
2.43.0