Re: [PATCH 3/8] xen/evtchn: modify evtchn_bind_interdomain to allocate specified port

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 05/07/2022 16:11, Jan Beulich wrote:
> On 22.06.2022 16:38, Rahul Singh wrote:
> > @@ -387,8 +392,19 @@ int evtchn_bind_interdomain(evtchn_bind_interdomain_t 
> > *bind)
> >           spin_lock(&ld->event_lock);
> >       }
> >   
> > -    if ( (lport = get_free_port(ld)) < 0 )
> > -        ERROR_EXIT(lport);
> > +    if ( lport != 0 )
> > +    {
> > +        if ( (rc = evtchn_allocate_port(ld, lport)) != 0 )
> > +            ERROR_EXIT_DOM(rc, ld);
> > +    }
> > +    else
> > +    {
> > +        int alloc_port = get_free_port(ld);
> > +
> > +        if ( alloc_port < 0 )
> > +            ERROR_EXIT_DOM(alloc_port, ld);
> > +        lport = alloc_port;
> > +    }
> This is then the 3rd instance of this pattern. I think the logic
> wants moving into get_free_port() (perhaps with a name change).
I think the code below would be suitable. I can send it or Rahul can 
re-use the commit [1]:
diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 
e6fb024218e949529c587b7c4755295786d6e7a7..757088580c2b2a3e55774f50b8ad7b3ec9243788 
100644 (file)
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -292,6 +292,18 @@ void evtchn_free(struct domain *d, struct evtchn *chn)
     xsm_evtchn_close_post(chn);
 }

+static int evtchn_get_port(struct domain *d, uint32_t port)
+{
+    int rc;
+
+    if ( port != 0 )
+        rc = evtchn_allocate_port(d, port);
+    else
+        rc = get_free_port(d);
+
+    return rc != 0 ? rc : port;
+}
+
 static long evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc)
 {
     struct evtchn *chn;
@@ -451,19 +463,10 @@ int evtchn_bind_virq(evtchn_bind_virq_t *bind, 
evtchn_port_t port)
     if ( read_atomic(&v->virq_to_evtchn[virq]) )
         ERROR_EXIT(-EEXIST);

-    if ( port != 0 )
-    {
-        if ( (rc = evtchn_allocate_port(d, port)) != 0 )
-            ERROR_EXIT(rc);
-    }
-    else
-    {
-        int alloc_port = get_free_port(d);
-
-        if ( alloc_port < 0 )
-            ERROR_EXIT(alloc_port);
-        port = alloc_port;
-    }
+    port = rc = evtchn_get_port(d, port);
+    if ( rc < 0 )
+        ERROR_EXIT(rc);
+    rc = 0;

     chn = evtchn_from_port(d, port);

[1] 
https://xenbits.xen.org/gitweb/?p=people/julieng/xen-unstable.git;a=commit;h=3860ed9915d6fee97a1088110ffd0a6f29f04d9a
> And of course like in the earlier patch the issue with sparse port
> numbers needs to be resolved.
>
> Jan
--
Julien Grall