KVM: Mask KVM_GET_SUPPORTED_CPUID data with Linux cpuid info

This allows Linux to mask cpuid bits if, for example, nx is enabled on only
some cpus.
Signed-off-by: NAvi Kivity <avi@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/x86.c

@@ -2227,6 +2227,11 @@ static int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
 	return r;
 }
 
+static void cpuid_mask(u32 *word, int wordnum)
+{
+	*word &= boot_cpu_data.x86_capability[wordnum];
+}
+
 static void do_cpuid_1_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 			   u32 index)
 {
@@ -2301,7 +2306,9 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 		break;
 	case 1:
 		entry->edx &= kvm_supported_word0_x86_features;
+		cpuid_mask(&entry->edx, 0);
 		entry->ecx &= kvm_supported_word4_x86_features;
+		cpuid_mask(&entry->ecx, 4);
 		/* we support x2apic emulation even if host does not support
 		 * it since we emulate x2apic in software */
 		entry->ecx |= F(X2APIC);
@@ -2392,7 +2399,9 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 		break;
 	case 0x80000001:
 		entry->edx &= kvm_supported_word1_x86_features;
+		cpuid_mask(&entry->edx, 1);
 		entry->ecx &= kvm_supported_word6_x86_features;
+		cpuid_mask(&entry->ecx, 6);
 		break;
 	}