--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -147,6 +147,11 @@ static bool virq_is_global(unsigned int
     return true;
 }
 
+static struct evtchn *_evtchn_from_port(const struct domain *d,
+                                        evtchn_port_t port)
+{
+    return port_is_valid(d, port) ? evtchn_from_port(d, port) : NULL;
+}
 
 static struct evtchn *alloc_evtchn_bucket(struct domain *d, unsigned int port)
 {
@@ -361,9 +366,9 @@ static long evtchn_bind_interdomain(evtc
         ERROR_EXIT(lport);
     lchn = evtchn_from_port(ld, lport);
 
-    if ( !port_is_valid(rd, rport) )
+    rchn = _evtchn_from_port(rd, rport);
+    if ( !rchn )
         ERROR_EXIT_DOM(-EINVAL, rd);
-    rchn = evtchn_from_port(rd, rport);
 
     double_evtchn_lock(lchn, rchn);
 
@@ -600,15 +605,12 @@ static long evtchn_bind_pirq(evtchn_bind
 int evtchn_close(struct domain *d1, int port1, bool guest)
 {
     struct domain *d2 = NULL;
-    struct evtchn *chn1, *chn2;
-    int            port2;
+    struct evtchn *chn1 = _evtchn_from_port(d1, port1), *chn2;
     long           rc = 0;
 
-    if ( !port_is_valid(d1, port1) )
+    if ( !chn1 )
         return -EINVAL;
 
-    chn1 = evtchn_from_port(d1, port1);
-
  again:
     write_lock(&d1->event_lock);
 
@@ -695,10 +697,8 @@ int evtchn_close(struct domain *d1, int
             goto out;
         }
 
-        port2 = chn1->u.interdomain.remote_port;
-        BUG_ON(!port_is_valid(d2, port2));
-
-        chn2 = evtchn_from_port(d2, port2);
+        chn2 = _evtchn_from_port(d2, chn1->u.interdomain.remote_port);
+        BUG_ON(!chn2);
         BUG_ON(chn2->state != ECS_INTERDOMAIN);
         BUG_ON(chn2->u.interdomain.remote_dom != d1);
 
@@ -736,15 +736,13 @@ int evtchn_close(struct domain *d1, int
 
 int evtchn_send(struct domain *ld, unsigned int lport)
 {
-    struct evtchn *lchn, *rchn;
+    struct evtchn *lchn = _evtchn_from_port(ld, lport), *rchn;
     struct domain *rd;
     int            rport, ret = 0;
 
-    if ( !port_is_valid(ld, lport) )
+    if ( !lchn )
         return -EINVAL;
 
-    lchn = evtchn_from_port(ld, lport);
-
     evtchn_read_lock(lchn);
 
     /* Guest cannot send via a Xen-attached event channel. */
@@ -956,7 +954,6 @@ int evtchn_status(evtchn_status_t *statu
 {
     struct domain   *d;
     domid_t          dom = status->dom;
-    int              port = status->port;
     struct evtchn   *chn;
     long             rc = 0;
 
@@ -964,14 +961,13 @@ int evtchn_status(evtchn_status_t *statu
     if ( d == NULL )
         return -ESRCH;
 
-    if ( !port_is_valid(d, port) )
+    chn = _evtchn_from_port(d, status->port);
+    if ( !chn )
     {
         rcu_unlock_domain(d);
         return -EINVAL;
     }
 
-    chn = evtchn_from_port(d, port);
-
     evtchn_read_lock(chn);
 
     if ( consumer_is_xen(chn) )
@@ -1036,11 +1032,10 @@ long evtchn_bind_vcpu(unsigned int port,
     if ( (v = domain_vcpu(d, vcpu_id)) == NULL )
         return -ENOENT;
 
-    if ( !port_is_valid(d, port) )
+    chn = _evtchn_from_port(d, port);
+    if ( !chn )
         return -EINVAL;
 
-    chn = evtchn_from_port(d, port);
-
     write_lock(&d->event_lock);
 
     /* Guest cannot re-bind a Xen-attached event channel. */
@@ -1086,13 +1081,11 @@ long evtchn_bind_vcpu(unsigned int port,
 int evtchn_unmask(unsigned int port)
 {
     struct domain *d = current->domain;
-    struct evtchn *evtchn;
+    struct evtchn *evtchn = _evtchn_from_port(d, port);
 
-    if ( unlikely(!port_is_valid(d, port)) )
+    if ( unlikely(!evtchn) )
         return -EINVAL;
 
-    evtchn = evtchn_from_port(d, port);
-
     evtchn_read_lock(evtchn);
 
     evtchn_port_unmask(d, evtchn);
@@ -1175,14 +1168,12 @@ static long evtchn_set_priority(const st
 {
     struct domain *d = current->domain;
     unsigned int port = set_priority->port;
-    struct evtchn *chn;
+    struct evtchn *chn = _evtchn_from_port(d, port);
     long ret;
 
-    if ( !port_is_valid(d, port) )
+    if ( !chn )
         return -EINVAL;
 
-    chn = evtchn_from_port(d, port);
-
     evtchn_read_lock(chn);
 
     ret = evtchn_port_set_priority(d, chn, set_priority->priority);
@@ -1408,10 +1399,10 @@ void free_xen_event_channel(struct domai
 
 void notify_via_xen_event_channel(struct domain *ld, int lport)
 {
-    struct evtchn *lchn, *rchn;
+    struct evtchn *lchn = _evtchn_from_port(ld, lport), *rchn;
     struct domain *rd;
 
-    if ( !port_is_valid(ld, lport) )
+    if ( !lchn )
     {
         /*
          * Make sure ->is_dying is read /after/ ->valid_evtchns, pairing
@@ -1422,8 +1413,6 @@ void notify_via_xen_event_channel(struct
         return;
     }
 
-    lchn = evtchn_from_port(ld, lport);
-
     if ( !evtchn_read_trylock(lchn) )
         return;
 
@@ -1577,16 +1566,17 @@ static void domain_dump_evtchn_info(stru
            "Polling vCPUs: {%*pbl}\n"
            "    port [p/m/s]\n", d->domain_id, d->max_vcpus, d->poll_mask);
 
-    for ( port = 1; port_is_valid(d, port); ++port )
+    for ( port = 1; ; ++port )
     {
-        struct evtchn *chn;
+        struct evtchn *chn = _evtchn_from_port(d, port);
         char *ssid;
 
+        if ( !chn )
+            break;
+
         if ( !(port & 0x3f) )
             process_pending_softirqs();
 
-        chn = evtchn_from_port(d, port);
-
         if ( !evtchn_read_trylock(chn) )
         {
             printk("    %4u in flux\n", port);
--- a/xen/include/xen/event.h
+++ b/xen/include/xen/event.h
@@ -120,7 +120,7 @@ static inline void evtchn_read_unlock(st
     read_unlock(&evtchn->lock);
 }
 
-static inline bool_t port_is_valid(struct domain *d, unsigned int p)
+static inline bool port_is_valid(const struct domain *d, evtchn_port_t p)
 {
     if ( p >= read_atomic(&d->valid_evtchns) )
         return false;
@@ -135,7 +135,8 @@ static inline bool_t port_is_valid(struc
     return true;
 }
 
-static inline struct evtchn *evtchn_from_port(struct domain *d, unsigned int p)
+static inline struct evtchn *evtchn_from_port(const struct domain *d,
+                                              evtchn_port_t p)
 {
     if ( p < EVTCHNS_PER_BUCKET )
         return &d->evtchn[array_index_nospec(p, EVTCHNS_PER_BUCKET)];
