Index: sys/xen/xen_intr.c
===================================================================
--- sys/xen/xen_intr.c
+++ sys/xen/xen_intr.c
@@ -388,6 +388,7 @@
     void *arg, enum intr_type flags, xen_intr_handle_t *port_handlep)
 {
 	struct xenisrc *isrc;
+	u_int cpu;
 	int error;
 
 	*isrcp = NULL;
@@ -399,11 +400,13 @@
 	isrc = xen_intr_alloc_isrc(params);
 	if (isrc == NULL)
 		return (ENOSPC);
+	cpu = isrc->xi_cpu;
 	mtx_lock(&xen_intr_isrc_lock);
 	if (xen_intr_port_to_isrc[isrc->xi_port] != NULL) {
 		xen_intr_port_to_isrc[isrc->xi_port]->xi_port = ~0U;
 		isrc->xi_cpu = xen_intr_port_to_isrc[isrc->xi_port]->xi_cpu;
-	}
+	} else
+		isrc->xi_cpu = 0;
 	xen_intr_port_to_isrc[isrc->xi_port] = isrc;
 	refcount_init(&isrc->xi_refcount, 1);
 	mtx_unlock(&xen_intr_isrc_lock);
@@ -412,13 +415,29 @@
 	*port_handlep = xen_intr_handle_from_isrc(isrc);
 
 #ifdef SMP
-	if (isrc->xi_type == EVTCHN_TYPE_PORT) {
+	if (cpu > mp_maxid) {
 		/*
 		 * By default all interrupts are assigned to vCPU#0
 		 * unless specified otherwise, so shuffle them to balance
 		 * the interrupt load.
 		 */
-		xen_intr_assign_cpu(isrc, intr_next_cpu(0));
+		cpu = intr_next_cpu(0);
+	}
+
+	error = xen_arch_intr_event_bind(isrc, cpu);
+	if (error != 0) { /* *very* unlikely */
+		xen_intr_release_isrc(isrc);
+		return (error);
+	}
+
+	if (isrc->xi_cpu != cpu) {
+		/*
+		 * Too early in the boot process for the generic interrupt
+		 * code to perform the binding.  Update our event channel
+		 * masks manually so events can't fire on the wrong cpu
+		 * during AP startup.
+		 */
+		xen_intr_assign_cpu(isrc, cpu);
 	}
 #endif
 
@@ -930,6 +949,7 @@
 	struct xenisrc *isrc;
 	struct xenisrc params = {
 		.xi_type = EVTCHN_TYPE_PORT,
+		.xi_cpu = ~0U,
 		.xi_port = local_port,
 		/*
 		 * The Event Channel API didn't open this port, so it is not
@@ -950,6 +970,7 @@
 	struct xenisrc *isrc;
 	struct xenisrc params = {
 		.xi_type = EVTCHN_TYPE_PORT,
+		.xi_cpu = ~0U,
 	};
 	struct evtchn_alloc_unbound alloc_unbound;
 	int error;
@@ -988,6 +1009,7 @@
 	struct xenisrc *isrc;
 	struct xenisrc params = {
 		.xi_type = EVTCHN_TYPE_PORT,
+		.xi_cpu = ~0U,
 	};
 	struct evtchn_bind_interdomain bind_interdomain;
 	int error;
@@ -1031,6 +1053,7 @@
 	struct xenisrc *isrc;
 	struct xenisrc params = {
 		.xi_type = EVTCHN_TYPE_VIRQ,
+		.xi_cpu = cpu,
 		.xi_virq = virq,
 	};
 	struct evtchn_bind_virq bind_virq = { .virq = virq, .vcpu = vcpu_id };
@@ -1050,11 +1073,6 @@
 	error = xen_intr_bind_isrc(&isrc, &params, device_get_nameunit(dev),
 	    filter, handler, arg, flags, port_handlep);
 
-#ifdef SMP
-	if (error == 0)
-		error = xen_arch_intr_event_bind(isrc, cpu);
-#endif
-
 	if (error != 0) {
 		evtchn_close_t close = { .port = params.xi_port };
 
@@ -1064,18 +1082,6 @@
 		return (error);
 	}
 
-#ifdef SMP
-	if (isrc->xi_cpu != cpu) {
-		/*
-		 * Too early in the boot process for the generic interrupt
-		 * code to perform the binding.  Update our event channel
-		 * masks manually so events can't fire on the wrong cpu
-		 * during AP startup.
-		 */
-		xen_intr_assign_cpu(isrc, cpu);
-	}
-#endif
-
 	/*
 	 * The Event Channel API opened this port, so it is
 	 * responsible for closing it automatically on unbind.
@@ -1094,6 +1100,7 @@
 	struct xenisrc *isrc;
 	struct xenisrc params = {
 		.xi_type = EVTCHN_TYPE_IPI,
+		.xi_cpu = cpu,
 	};
 	struct evtchn_bind_ipi bind_ipi = { .vcpu = vcpu_id };
 	/* Same size as the one used by intr_handler->ih_name. */
@@ -1124,16 +1131,6 @@
 		return (error);
 	}
 
-	if (isrc->xi_cpu != cpu) {
-		/*
-		 * Too early in the boot process for the generic interrupt
-		 * code to perform the binding.  Update our event channel
-		 * masks manually so events can't fire on the wrong cpu
-		 * during AP startup.
-		 */
-		xen_intr_assign_cpu(isrc, cpu);
-	}
-
 	/*
 	 * The Event Channel API opened this port, so it is
 	 * responsible for closing it automatically on unbind.