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

[Rahul Singh <rahul.singh@xxxxxxx>]

evtchn_bind_interdomain() always allocates the next available local
port. Static event channel support for dom0less domains requires
allocating a specified port.

Modify the evtchn_bind_interdomain to accept the port number as an
argument and allocate the specified port if available. If the port
number argument is zero, the next available port will be allocated.

Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
---
 xen/common/event_channel.c | 26 +++++++++++++++++++++-----
 xen/include/xen/event.h    |  3 ++-
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 80a88c1544..bf5dc2c8ad 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -363,11 +363,16 @@ static void double_evtchn_unlock(struct evtchn *lchn, 
struct evtchn *rchn)
     evtchn_write_unlock(rchn);
 }
 
-int evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind)
+/*
+ * If lport is zero get the next free port and allocate. If port is non-zero
+ * allocate the specified lport.
+ */
+int evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind,
+                            evtchn_port_t lport)
 {
     struct evtchn *lchn, *rchn;
     struct domain *ld = current->domain, *rd;
-    int            lport, rc;
+    int            rc;
     evtchn_port_t  rport = bind->remote_port;
     domid_t        rdom = bind->remote_dom;
 
@@ -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;
+    }
     lchn = evtchn_from_port(ld, lport);
 
     rchn = _evtchn_from_port(rd, rport);
@@ -1232,7 +1248,7 @@ long cf_check do_event_channel_op(int cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg)
         struct evtchn_bind_interdomain bind_interdomain;
         if ( copy_from_guest(&bind_interdomain, arg, 1) != 0 )
             return -EFAULT;
-        rc = evtchn_bind_interdomain(&bind_interdomain);
+        rc = evtchn_bind_interdomain(&bind_interdomain, 0);
         if ( !rc && __copy_to_guest(arg, &bind_interdomain, 1) )
             rc = -EFAULT; /* Cleaning up here would be a mess! */
         break;
diff --git a/xen/include/xen/event.h b/xen/include/xen/event.h
index 48820e393e..6e26879793 100644
--- a/xen/include/xen/event.h
+++ b/xen/include/xen/event.h
@@ -76,7 +76,8 @@ int __must_check evtchn_alloc_unbound(evtchn_alloc_unbound_t 
*alloc,
                                       evtchn_port_t port);
 
 /* Bind an event channel port to interdomain */
-int __must_check evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind);
+int __must_check evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind,
+                                         evtchn_port_t port);
 
 /* Unmask a local event-channel port. */
 int evtchn_unmask(unsigned int port);
-- 
2.25.1