[PATCH v2 4/7] xen/evtchn: modify evtchn_bind_interdomain to support static evtchn

[Rahul Singh <rahul.singh@xxxxxxx>]

Static event channel support will be added for dom0less domains. Modify
evtchn_bind_interdomain to support static evtchn.

It is necessary to have access to the evtchn_bind_interdomain function
to do that, so make evtchn_bind_interdomain global and also make it
__must_check.

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.

evtchn_bind_interdomain() finds the local domain from "current->domain"
pointer. evtchn_bind_interdomain() will be called from the XEN to create
static event channel during domain creation. "current" pointer is not
valid at that time, therefore modify the evtchn_bind_interdomain() to
pass domain as an argument.

Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
---
Changes in v2:
 - Merged patches related to evtchn_bind_interdomain in one patch
---
---
 xen/common/event_channel.c | 20 ++++++++++++++------
 xen/include/xen/event.h    |  5 +++++
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 194f5346fb..eed0e94d07 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -373,11 +373,16 @@ static void double_evtchn_unlock(struct evtchn *lchn, 
struct evtchn *rchn)
     evtchn_write_unlock(rchn);
 }
 
-static 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, struct domain *ld,
+                            evtchn_port_t lport)
 {
     struct evtchn *lchn, *rchn;
-    struct domain *ld = current->domain, *rd;
-    int            lport, rc;
+    struct domain *rd;
+    int            rc;
     evtchn_port_t  rport = bind->remote_port;
     domid_t        rdom = bind->remote_dom;
 
@@ -397,8 +402,11 @@ static int 
evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind)
         write_lock(&ld->event_lock);
     }
 
-    if ( (lport = get_free_port(ld)) < 0 )
-        ERROR_EXIT(lport);
+    lport = rc = evtchn_get_port(ld, lport);
+    if ( rc < 0 )
+        ERROR_EXIT(rc);
+    rc = 0;
+
     lchn = evtchn_from_port(ld, lport);
 
     rchn = _evtchn_from_port(rd, rport);
@@ -1231,7 +1239,7 @@ long 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, current->domain, 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 f3021fe304..f29b1123d9 100644
--- a/xen/include/xen/event.h
+++ b/xen/include/xen/event.h
@@ -74,6 +74,11 @@ int evtchn_allocate_port(struct domain *d, unsigned int 
port);
 /* Allocate a new event channel */
 int __must_check evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc);
 
+/* Bind an event channel port to interdomain */
+int __must_check evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind,
+                                         struct domain *ld,
+                                         evtchn_port_t port);
+
 /* Unmask a local event-channel port. */
 int evtchn_unmask(unsigned int port);
 
-- 
2.25.1