Add DOMCTL to limit the number of event channels a domain may use

Add XEN_DOMCTL_set_max_evtchn which may be used during domain creation to
set the maximum event channel port a domain may use.  This may be used to
limit the amount of Xen resources (global mapping space and xenheap) that
a domain may use for event channels.

A domain that does not have a limit set may use all the event channels
supported by the event channel ABI in use.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Keir Fraser <keir@xen.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 0c0bbe494f..34efd24bb9 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -168,10 +168,14 @@ static int get_free_port(struct domain *d)
         return -EINVAL;
 
     for ( port = 0; port_is_valid(d, port); port++ )
+    {
+        if ( port > d->max_evtchn_port )
+            return -ENOSPC;
         if ( evtchn_from_port(d, port)->state == ECS_FREE )
             return port;
+    }
 
-    if ( port == d->max_evtchns )
+    if ( port == d->max_evtchns || port > d->max_evtchn_port )
         return -ENOSPC;
 
     if ( !group_from_port(d, port) )
@@ -1230,6 +1234,7 @@ void evtchn_check_pollers(struct domain *d, unsigned int port)
 int evtchn_init(struct domain *d)
 {
     evtchn_2l_init(d);
+    d->max_evtchn_port = INT_MAX;
 
     d->evtchn = alloc_evtchn_bucket(d, 0);
     if ( !d->evtchn )