KVM: x86: Add a VALID_MASK for the flag in kvm_msr_filter

Add the mask KVM_MSR_FILTER_VALID_MASK for the flag in the struct
kvm_msr_filter.  This makes it easier to introduce new flags in the
future.

No functional change intended.
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Message-Id: <20220921151525.904162-4-aaronlewis@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/uapi/asm/kvm.h

@@ -226,6 +226,7 @@ struct kvm_msr_filter {
 #define KVM_MSR_FILTER_DEFAULT_ALLOW (0 << 0)
 #endif
 #define KVM_MSR_FILTER_DEFAULT_DENY  (1 << 0)
+#define KVM_MSR_FILTER_VALID_MASK (KVM_MSR_FILTER_DEFAULT_DENY)
 	__u32 flags;
 	struct kvm_msr_filter_range ranges[KVM_MSR_FILTER_MAX_RANGES];
 };

arch/x86/kvm/x86.c

@@ -6441,7 +6441,7 @@ static int kvm_vm_ioctl_set_msr_filter(struct kvm *kvm,
 	int r = 0;
 	u32 i;
 
-	if (filter->flags & ~KVM_MSR_FILTER_DEFAULT_DENY)
+	if (filter->flags & ~KVM_MSR_FILTER_VALID_MASK)
 		return -EINVAL;
 
 	for (i = 0; i < ARRAY_SIZE(filter->ranges); i++)