[PATCH v2] tools/xenstore: don't store domU's mfn of ring page in xenstored

[Juergen Gross <jgross@xxxxxxxx>]

The XS_INTRODUCE command has two parameters: the mfn (or better: gfn)
of the domain's xenstore ring page and the event channel of the
domain for communicating with Xenstore.

The gfn is not really needed. It is stored in the per-domain struct
in xenstored and in case of another XS_INTRODUCE for the domain it
is tested to match the original value. If it doesn't match the
command is aborted via EINVAL.

Today there aren't multiple XS_INTRODUCE requests for the same domain
issued, so the mfn/gfn can just be ignored and multiple XS_INTRODUCE
commands can be rejected without testing the mfn/gfn.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
V2:
- remove mfn from struct domain (Julien Grall)
- replace mfn by gfn in comments (Julien Grall)
---
 tools/xenstore/xenstored_domain.c | 53 +++++++++++++++------------------------
 1 file changed, 20 insertions(+), 33 deletions(-)

diff --git a/tools/xenstore/xenstored_domain.c 
b/tools/xenstore/xenstored_domain.c
index 5858185211..1ca11e5e9e 100644
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -55,10 +55,6 @@ struct domain
           repeated domain introductions. */
        evtchn_port_t remote_port;
 
-       /* The mfn associated with the event channel, used only to validate
-          repeated domain introductions. */
-       unsigned long mfn;
-
        /* Domain path in store. */
        char *path;
 
@@ -363,13 +359,12 @@ static void domain_conn_reset(struct domain *domain)
        domain->interface->rsp_cons = domain->interface->rsp_prod = 0;
 }
 
-/* domid, mfn, evtchn, path */
+/* domid, gfn, evtchn, path */
 int do_introduce(struct connection *conn, struct buffered_data *in)
 {
        struct domain *domain;
        char *vec[3];
        unsigned int domid;
-       unsigned long mfn;
        evtchn_port_t port;
        int rc;
        struct xenstore_domain_interface *interface;
@@ -381,7 +376,7 @@ int do_introduce(struct connection *conn, struct 
buffered_data *in)
                return EACCES;
 
        domid = atoi(vec[0]);
-       mfn = atol(vec[1]);
+       /* Ignore the gfn, we don't need it. */
        port = atoi(vec[2]);
 
        /* Sanity check args. */
@@ -390,34 +385,26 @@ int do_introduce(struct connection *conn, struct 
buffered_data *in)
 
        domain = find_domain_by_domid(domid);
 
-       if (domain == NULL) {
-               interface = map_interface(domid);
-               if (!interface)
-                       return errno;
-               /* Hang domain off "in" until we're finished. */
-               domain = new_domain(in, domid, port);
-               if (!domain) {
-                       rc = errno;
-                       unmap_interface(interface);
-                       return rc;
-               }
-               domain->interface = interface;
-               domain->mfn = mfn;
-
-               /* Now domain belongs to its connection. */
-               talloc_steal(domain->conn, domain);
-
-               fire_watches(NULL, in, "@introduceDomain", false);
-       } else if ((domain->mfn == mfn) && (domain->conn != conn)) {
-               /* Use XS_INTRODUCE for recreating the xenbus event-channel. */
-               if (domain->port)
-                       xenevtchn_unbind(xce_handle, domain->port);
-               rc = xenevtchn_bind_interdomain(xce_handle, domid, port);
-               domain->port = (rc == -1) ? 0 : rc;
-               domain->remote_port = port;
-       } else
+       if (domain)
                return EINVAL;
 
+       interface = map_interface(domid);
+       if (!interface)
+               return errno;
+       /* Hang domain off "in" until we're finished. */
+       domain = new_domain(in, domid, port);
+       if (!domain) {
+               rc = errno;
+               unmap_interface(interface);
+               return rc;
+       }
+       domain->interface = interface;
+
+       /* Now domain belongs to its connection. */
+       talloc_steal(domain->conn, domain);
+
+       fire_watches(NULL, in, "@introduceDomain", false);
+
        domain_conn_reset(domain);
 
        send_ack(conn, XS_INTRODUCE);
-- 
2.16.4