diff --git a/xen/common/event_2l.c b/xen/common/event_2l.c
index e1dbb860f4..a229d35271 100644
--- a/xen/common/event_2l.c
+++ b/xen/common/event_2l.c
@@ -103,7 +103,6 @@ static const struct evtchn_port_ops evtchn_port_ops_2l =
 void evtchn_2l_init(struct domain *d)
 {
     d->evtchn_port_ops = &evtchn_port_ops_2l;
-    d->max_evtchns = BITS_PER_EVTCHN_WORD(d) * BITS_PER_EVTCHN_WORD(d);
 }
 
 /*
diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 53c17bd354..08ffe0f063 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -151,7 +151,7 @@ static void free_evtchn_bucket(struct domain *d, struct evtchn *bucket)
 
 int evtchn_allocate_port(struct domain *d, evtchn_port_t port)
 {
-    if ( port > d->max_evtchn_port || port >= d->max_evtchns )
+    if ( port > d->max_evtchn_port || port >= max_evtchns(d) )
         return -ENOSPC;
 
     if ( port_is_valid(d, port) )
@@ -1396,13 +1396,11 @@ static void domain_dump_evtchn_info(struct domain *d)
 
     spin_lock(&d->event_lock);
 
-    for ( port = 1; port < d->max_evtchns; ++port )
+    for ( port = 1; port_is_valid(d, port); ++port )
     {
         const struct evtchn *chn;
         char *ssid;
 
-        if ( !port_is_valid(d, port) )
-            continue;
         chn = evtchn_from_port(d, port);
         if ( chn->state == ECS_FREE )
             continue;
diff --git a/xen/common/event_fifo.c b/xen/common/event_fifo.c
index 230f440f14..2f13d92128 100644
--- a/xen/common/event_fifo.c
+++ b/xen/common/event_fifo.c
@@ -478,7 +478,7 @@ static void cleanup_event_array(struct domain *d)
     d->evtchn_fifo = NULL;
 }
 
-static void setup_ports(struct domain *d)
+static void setup_ports(struct domain *d, unsigned int prev_evtchns)
 {
     unsigned int port;
 
@@ -488,7 +488,7 @@ static void setup_ports(struct domain *d)
      * - save its pending state.
      * - set default priority.
      */
-    for ( port = 1; port < d->max_evtchns; port++ )
+    for ( port = 1; port < prev_evtchns; port++ )
     {
         struct evtchn *evtchn;
 
@@ -546,6 +546,8 @@ int evtchn_fifo_init_control(struct evtchn_init_control *init_control)
     if ( !d->evtchn_fifo )
     {
         struct vcpu *vcb;
+        /* Latch the value before it changes during setup_event_array(). */
+        unsigned int prev_evtchns = max_evtchns(d);
 
         for_each_vcpu ( d, vcb ) {
             rc = setup_control_block(vcb);
@@ -562,8 +564,7 @@ int evtchn_fifo_init_control(struct evtchn_init_control *init_control)
             goto error;
 
         d->evtchn_port_ops = &evtchn_port_ops_fifo;
-        d->max_evtchns = EVTCHN_FIFO_NR_CHANNELS;
-        setup_ports(d);
+        setup_ports(d, prev_evtchns);
     }
     else
         rc = map_control_block(v, gfn, offset);
diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index cb49a8bc02..ab94d2ec3a 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -1428,7 +1428,7 @@ static long do_poll(struct sched_poll *sched_poll)
             goto out;
 
         rc = -EINVAL;
-        if ( port >= d->max_evtchns )
+        if ( !port_is_valid(d, port) )
             goto out;
 
         rc = 0;
diff --git a/xen/include/xen/event.h b/xen/include/xen/event.h
index c35f4b23b6..e1b299e8df 100644
--- a/xen/include/xen/event.h
+++ b/xen/include/xen/event.h
@@ -105,6 +105,12 @@ void notify_via_xen_event_channel(struct domain *ld, int lport);
 #define bucket_from_port(d, p) \
     ((group_from_port(d, p))[((p) % EVTCHNS_PER_GROUP) / EVTCHNS_PER_BUCKET])
 
+static inline unsigned int max_evtchns(const struct domain *d)
+{
+    return d->evtchn_fifo ? EVTCHN_FIFO_NR_CHANNELS
+                          : BITS_PER_EVTCHN_WORD(d) * BITS_PER_EVTCHN_WORD(d);
+}
+
 static inline bool_t port_is_valid(struct domain *d, unsigned int p)
 {
     if ( p >= read_atomic(&d->valid_evtchns) )
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index e9ce43cc9a..33d716ef77 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -359,7 +359,6 @@ struct domain
     /* Event channel information. */
     struct evtchn   *evtchn;                         /* first bucket only */
     struct evtchn  **evtchn_group[NR_EVTCHN_GROUPS]; /* all other buckets */
-    unsigned int     max_evtchns;     /* number supported by ABI */
     unsigned int     max_evtchn_port; /* max permitted port number */
     unsigned int     valid_evtchns;   /* number of allocated event channels */
     spinlock_t       event_lock;