[XEN PATCH 2/7] xen: introduce _evtchn_alloc_unbound

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

From: Luca Miccio <lucmiccio@xxxxxxxxx>

The xenstore event channel will be allocated for dom0less domains. It is
necessary to have access to the evtchn_alloc_unbound function to do
that.

Factor out the part that actually allocates the event channel from
evtchn_alloc_unbound and introduce this new function as
_evtchn_alloc_unbound. (xsm_evtchn_unbound wouldn't work for a call
originated from Xen.)

Signed-off-by: Luca Miccio <lucmiccio@xxxxxxxxx>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
CC: Julien Grall <julien@xxxxxxx>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>
CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: George Dunlap <george.dunlap@xxxxxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
---
 xen/common/event_channel.c | 49 +++++++++++++++++++++++++-------------
 xen/include/xen/event.h    |  3 +++
 2 files changed, 36 insertions(+), 16 deletions(-)

diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index da88ad141a..8a19bbf7ae 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -18,6 +18,7 @@
 
 #include <xen/init.h>
 #include <xen/lib.h>
+#include <xen/err.h>
 #include <xen/errno.h>
 #include <xen/sched.h>
 #include <xen/irq.h>
@@ -284,11 +285,32 @@ void evtchn_free(struct domain *d, struct evtchn *chn)
     xsm_evtchn_close_post(chn);
 }
 
-static int evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc)
+struct evtchn *_evtchn_alloc_unbound(struct domain *d, domid_t remote_dom)
 {
     struct evtchn *chn;
+    int port;
+
+    if ( (port = get_free_port(d)) < 0 )
+        return ERR_PTR(port);
+    chn = evtchn_from_port(d, port);
+
+    evtchn_write_lock(chn);
+
+    chn->state = ECS_UNBOUND;
+    if ( (chn->u.unbound.remote_domid = remote_dom) == DOMID_SELF )
+        chn->u.unbound.remote_domid = current->domain->domain_id;
+    evtchn_port_init(d, chn);
+
+    evtchn_write_unlock(chn);
+
+    return chn;
+}
+
+static int evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc)
+{
+    struct evtchn *chn = NULL;
     struct domain *d;
-    int            port, rc;
+    int            rc;
     domid_t        dom = alloc->dom;
 
     d = rcu_lock_domain_by_any_id(dom);
@@ -297,27 +319,22 @@ static int evtchn_alloc_unbound(evtchn_alloc_unbound_t 
*alloc)
 
     spin_lock(&d->event_lock);
 
-    if ( (port = get_free_port(d)) < 0 )
-        ERROR_EXIT_DOM(port, d);
-    chn = evtchn_from_port(d, port);
+    chn = _evtchn_alloc_unbound(d, alloc->remote_dom);
+    if ( IS_ERR(chn) )
+    {
+        rc = PTR_ERR(chn);
+        ERROR_EXIT_DOM(rc, d);
+    }
 
     rc = xsm_evtchn_unbound(XSM_TARGET, d, chn, alloc->remote_dom);
     if ( rc )
         goto out;
 
-    evtchn_write_lock(chn);
-
-    chn->state = ECS_UNBOUND;
-    if ( (chn->u.unbound.remote_domid = alloc->remote_dom) == DOMID_SELF )
-        chn->u.unbound.remote_domid = current->domain->domain_id;
-    evtchn_port_init(d, chn);
-
-    evtchn_write_unlock(chn);
-
-    alloc->port = port;
+    alloc->port = chn->port;
 
  out:
-    check_free_port(d, port);
+    if ( chn != NULL )
+        check_free_port(d, chn->port);
     spin_unlock(&d->event_lock);
     rcu_unlock_domain(d);
 
diff --git a/xen/include/xen/event.h b/xen/include/xen/event.h
index 21c95e14fd..6aedbccbf1 100644
--- a/xen/include/xen/event.h
+++ b/xen/include/xen/event.h
@@ -68,6 +68,9 @@ int evtchn_close(struct domain *d1, int port1, bool guest);
 /* Free an event channel. */
 void evtchn_free(struct domain *d, struct evtchn *chn);
 
+/* Create a new event channel port */
+struct evtchn *_evtchn_alloc_unbound(struct domain *d, domid_t remote_dom);
+
 /* Allocate a specific event channel port. */
 int evtchn_allocate_port(struct domain *d, unsigned int port);
 
-- 
2.25.1