3 files changed, 81 insertions, 2 deletions

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 6e075cdd0c6..a3bcd6175f4 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -87,6 +87,7 @@ enum xen_irq_type {
  */
 struct irq_info {
         struct list_head list;
+        int refcnt;
         enum xen_irq_type type; /* type */
         unsigned irq;
         unsigned short evtchn;  /* event channel */
@@ -406,6 +407,7 @@ static void xen_irq_init(unsigned irq)
                 panic("Unable to allocate metadata for IRQ%d\n", irq);
 
         info->type = IRQT_UNBOUND;
+        info->refcnt = -1;
 
         irq_set_handler_data(irq, info);
 
@@ -469,6 +471,8 @@ static void xen_free_irq(unsigned irq)
 
         irq_set_handler_data(irq, NULL);
 
+        WARN_ON(info->refcnt > 0);
+
         kfree(info);
 
         /* Legacy IRQ descriptors are managed by the arch. */
@@ -637,7 +641,7 @@ int xen_bind_pirq_gsi_to_irq(unsigned gsi,
         if (irq != -1) {
                 printk(KERN_INFO "xen_map_pirq_gsi: returning irq %d for gsi %u\n",
                        irq, gsi);
-                goto out;       /* XXX need refcount? */
+                goto out;
         }
 
         irq = xen_allocate_irq_gsi(gsi);
@@ -939,9 +943,16 @@ static void unbind_from_irq(unsigned int irq)
 {
         struct evtchn_close close;
         int evtchn = evtchn_from_irq(irq);
+        struct irq_info *info = irq_get_handler_data(irq);
 
         mutex_lock(&irq_mapping_update_lock);
 
+        if (info->refcnt > 0) {
+                info->refcnt--;
+                if (info->refcnt != 0)
+                        goto done;
+        }
+
         if (VALID_EVTCHN(evtchn)) {
                 close.port = evtchn;
                 if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
@@ -970,6 +981,7 @@ static void unbind_from_irq(unsigned int irq)
 
         xen_free_irq(irq);
 
+ done:
         mutex_unlock(&irq_mapping_update_lock);
 }
 
@@ -1065,6 +1077,66 @@ void unbind_from_irqhandler(unsigned int irq, void *dev_id)
 }
 EXPORT_SYMBOL_GPL(unbind_from_irqhandler);
 
+int evtchn_make_refcounted(unsigned int evtchn)
+{
+        int irq = evtchn_to_irq[evtchn];
+        struct irq_info *info;
+
+        if (irq == -1)
+                return -ENOENT;
+
+        info = irq_get_handler_data(irq);
+
+        if (!info)
+                return -ENOENT;
+
+        WARN_ON(info->refcnt != -1);
+
+        info->refcnt = 1;
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(evtchn_make_refcounted);
+
+int evtchn_get(unsigned int evtchn)
+{
+        int irq;
+        struct irq_info *info;
+        int err = -ENOENT;
+
+        mutex_lock(&irq_mapping_update_lock);
+
+        irq = evtchn_to_irq[evtchn];
+        if (irq == -1)
+                goto done;
+
+        info = irq_get_handler_data(irq);
+
+        if (!info)
+                goto done;
+
+        err = -EINVAL;
+        if (info->refcnt <= 0)
+                goto done;
+
+        info->refcnt++;
+        err = 0;
+ done:
+        mutex_unlock(&irq_mapping_update_lock);
+
+        return err;
+}
+EXPORT_SYMBOL_GPL(evtchn_get);
+
+void evtchn_put(unsigned int evtchn)
+{
+        int irq = evtchn_to_irq[evtchn];
+        if (WARN_ON(irq == -1))
+                return;
+        unbind_from_irq(irq);
+}
+EXPORT_SYMBOL_GPL(evtchn_put);
+
 void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
 {
         int irq = per_cpu(ipi_to_irq, cpu)[vector];
diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
index dbc13e94b61..b1f60a0c0be 100644
--- a/drivers/xen/evtchn.c
+++ b/drivers/xen/evtchn.c
@@ -268,7 +268,7 @@ static int evtchn_bind_to_user(struct per_user_data *u, int port)
         rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
                                        u->name, (void *)(unsigned long)port);
         if (rc >= 0)
-                rc = 0;
+                rc = evtchn_make_refcounted(port);
 
         return rc;
 }
diff --git a/include/xen/events.h b/include/xen/events.h
index d287997d3ea..0f773708e02 100644
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -37,6 +37,13 @@ int bind_interdomain_evtchn_to_irqhandler(unsigned int remote_domain,
  */
 void unbind_from_irqhandler(unsigned int irq, void *dev_id);
 
+/*
+ * Allow extra references to event channels exposed to userspace by evtchn
+ */
+int evtchn_make_refcounted(unsigned int evtchn);
+int evtchn_get(unsigned int evtchn);
+void evtchn_put(unsigned int evtchn);
+
 void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector);
 int resend_irq_on_evtchn(unsigned int irq);
 void rebind_evtchn_irq(int evtchn, int irq);