diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 53777f8..067365b 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -51,6 +51,8 @@
 
 #define consumer_is_xen(e) (!!(e)->xen_consumer)
 
+static long __evtchn_close(struct domain *d, int port);
+
 /*
  * The function alloc_unbound_xen_event_channel() allows an arbitrary
  * notifier function to be specified. However, very few unique functions
@@ -161,18 +163,18 @@ static long evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc)
 {
     struct evtchn *chn;
     struct domain *d;
-    int            port;
+    evtchn_port_t  port;
     domid_t        dom = alloc->dom;
-    long           rc;
+    int            rc;
 
     rc = rcu_lock_target_domain_by_id(dom, &d);
     if ( rc )
         return rc;
 
-    spin_lock(&d->event_lock);
+    rc = evtchn_alloc_unbound_domain(d, &port);
+    if ( rc )
+        ERROR_EXIT_DOM(rc, d);
 
-    if ( (port = get_free_port(d)) < 0 )
-        ERROR_EXIT_DOM(port, d);
     chn = evtchn_from_port(d, port);
 
     rc = xsm_evtchn_unbound(d, chn, alloc->remote_dom);
@@ -186,12 +188,31 @@ static long evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc)
     alloc->port = port;
 
  out:
-    spin_unlock(&d->event_lock);
     rcu_unlock_domain(d);
 
     return rc;
 }
 
+int evtchn_alloc_unbound_domain(struct domain *d, evtchn_port_t *port)
+{
+    struct evtchn *chn;
+    int            free_port = 0;
+
+    spin_lock(&d->event_lock);
+
+    if ( (free_port = get_free_port(d)) < 0 )
+        goto out;
+    chn = evtchn_from_port(d, free_port);
+    chn->state = ECS_UNBOUND;
+    chn->u.unbound.remote_domid = DOMID_INVALID;
+    *port = free_port;
+    /* Everything is fine, returns 0 */
+    free_port = 0;
+
+ out:
+    spin_unlock(&d->event_lock);
+    return free_port;
+}
 
 static long evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind)
 {
diff --git a/xen/include/xen/event.h b/xen/include/xen/event.h
index 71c3e92..d89b0c1 100644
--- a/xen/include/xen/event.h
+++ b/xen/include/xen/event.h
@@ -69,6 +69,8 @@ int guest_enabled_event(struct vcpu *v, uint32_t virq);
 /* Notify remote end of a Xen-attached event channel.*/
 void notify_via_xen_event_channel(struct domain *ld, int lport);
 
+int evtchn_alloc_unbound_domain(struct domain *d, evtchn_port_t *port);
+
 /* Internal event channel object accessors */
 #define bucket_from_port(d,p) \
     ((d)->evtchn[(p)/EVTCHNS_PER_BUCKET])