[Xen-devel] [PATCHv2 2/5] evtchn: simplify port_is_valid()

[David Vrabel <david.vrabel@xxxxxxxxxx>]

By keeping a count of the number of currently valid event channels,
port_is_valid() can be simplified.

d->valid_evtchns can also be tested without holding d->event_lock which
will be useful later on.

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
---
v2:
- Used unsigned int for d->valid_evtchns.
---
 xen/common/event_channel.c |    3 +++
 xen/include/xen/event.h    |    4 +---
 xen/include/xen/sched.h    |    5 +++--
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 947880f..fd48646 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -189,6 +189,8 @@ static int get_free_port(struct domain *d)
         return -ENOMEM;
     bucket_from_port(d, port) = chn;
 
+    write_atomic(&d->valid_evtchns, d->valid_evtchns + EVTCHNS_PER_BUCKET);
+
     return port;
 }
 
@@ -1254,6 +1256,7 @@ int evtchn_init(struct domain *d)
     d->evtchn = alloc_evtchn_bucket(d, 0);
     if ( !d->evtchn )
         return -ENOMEM;
+    d->valid_evtchns = EVTCHNS_PER_BUCKET;
 
     spin_lock_init_prof(d, event_lock);
     if ( get_free_port(d) != 0 )
diff --git a/xen/include/xen/event.h b/xen/include/xen/event.h
index 690f865..a08ecdb 100644
--- a/xen/include/xen/event.h
+++ b/xen/include/xen/event.h
@@ -91,9 +91,7 @@ static inline bool_t port_is_valid(struct domain *d, unsigned 
int p)
         return 0;
     if ( !d->evtchn )
         return 0;
-    if ( p < EVTCHNS_PER_BUCKET )
-        return 1;
-    return group_from_port(d, p) != NULL && bucket_from_port(d, p) != NULL;
+    return p < read_atomic(&d->valid_evtchns);
 }
 
 static inline struct evtchn *evtchn_from_port(struct domain *d, unsigned int p)
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 80c6f62..604d047 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -336,8 +336,9 @@ 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;
-    unsigned int     max_evtchn_port;
+    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;
     const struct evtchn_port_ops *evtchn_port_ops;
     struct evtchn_fifo_domain *evtchn_fifo;
-- 
1.7.10.4


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