KVM: x86: Mask off reserved bits in CPUID.8000001AH

commit 079f688 upstream.

KVM_GET_SUPPORTED_CPUID should only enumerate features that KVM
actually supports. In the case of CPUID.8000001AH, only three bits are
currently defined. The 125 reserved bits should be masked off.

Fixes: 24c82e5 ("KVM: Sanitize cpuid")
Signed-off-by: Jim Mattson <jmattson@google.com>
Message-Id: <20220929225203.2234702-4-jmattson@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/kvm/cpuid.c

@@ -956,6 +956,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		entry->ecx = entry->edx = 0;
 		break;
 	case 0x8000001a:
+		entry->eax &= GENMASK(2, 0);
+		entry->ebx = entry->ecx = entry->edx = 0;
+		break;
 	case 0x8000001e:
 		break;
 	case 0x8000001F: