kvm/x86: Skip SynIC vector check for QEMU side

QEMU zero-inits Hyper-V SynIC vectors. We should allow that,
and don't reject zero values if set by the host.
Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/hyperv.c

@@ -72,12 +72,13 @@ static bool synic_has_vector_auto_eoi(struct kvm_vcpu_hv_synic *synic,
 	return false;
 }
 
-static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint, u64 data)
+static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint,
+			  u64 data, bool host)
 {
 	int vector;
 
 	vector = data & HV_SYNIC_SINT_VECTOR_MASK;
-	if (vector < 16)
+	if (vector < 16 && !host)
 		return 1;
 	/*
 	 * Guest may configure multiple SINTs to use the same vector, so
@@ -247,7 +248,7 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
 		break;
 	}
 	case HV_X64_MSR_SINT0 ... HV_X64_MSR_SINT15:
-		ret = synic_set_sint(synic, msr - HV_X64_MSR_SINT0, data);
+		ret = synic_set_sint(synic, msr - HV_X64_MSR_SINT0, data, host);
 		break;
 	default:
 		ret = 1;