KVM: x86: check validity of argument to KVM_SET_MP_STATE

An invalid argument to KVM_SET_MP_STATE has no effect other than making the
vCPU fail to run at the next KVM_RUN.  Since it is extremely unlikely that
any userspace is relying on it, fail with -EINVAL just like for other
architectures.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -10669,7 +10669,8 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu)
 	case KVM_MP_STATE_INIT_RECEIVED:
 		break;
 	default:
-		return -EINTR;
+		WARN_ON_ONCE(1);
+		break;
 	}
 	return 1;
 }
@@ -11110,9 +11111,22 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
 
 	vcpu_load(vcpu);
 
-	if (!lapic_in_kernel(vcpu) &&
-	    mp_state->mp_state != KVM_MP_STATE_RUNNABLE)
+	switch (mp_state->mp_state) {
+	case KVM_MP_STATE_UNINITIALIZED:
+	case KVM_MP_STATE_HALTED:
+	case KVM_MP_STATE_AP_RESET_HOLD:
+	case KVM_MP_STATE_INIT_RECEIVED:
+	case KVM_MP_STATE_SIPI_RECEIVED:
+		if (!lapic_in_kernel(vcpu))
+			goto out;
+		break;
+
+	case KVM_MP_STATE_RUNNABLE:
+		break;
+
+	default:
 		goto out;
+	}
 
 	/*
 	 * KVM_MP_STATE_INIT_RECEIVED means the processor is in