libxl: trigger attach events for devices attached before xl devd startup

When this daemon is started after creating backend device, that device
will not be configured.

Racy situation:
1. driver domain is started
2. frontend domain is started (just after kicking driver domain off)
3. device in frontend domain is connected to the backend (as specified
   in frontend domain configuration)
4. xl devd is started in driver domain

End result is that backend device in driver domain is not configured
(like network interface is not enabled), so the device doesn't work.

Fix this by artifically triggering events for devices already present in
xenstore before xl devd is started. Do this only after xenstore watch is
already registered, and only for devices not already initialized (in
XenbusStateInitWait state).

Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 2cf745153f2b6e2da60b0b6e9d99b5cc63540d62..b5f90844c678c84c76e33fea00a433f4b8342450 100644 (file)
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -4658,6 +4658,12 @@ int libxl_device_events_handler(libxl_ctx *ctx,
     uint32_t domid;
     libxl__ddomain ddomain;
     char *be_path;
+    char **kinds = NULL, **domains = NULL, **devs = NULL;
+    const char *sstate;
+    char *state_path;
+    int state;
+    unsigned int nkinds, ndomains, ndevs;
+    int i, j, k;
 
     ddomain.ao = ao;
     LIBXL_SLIST_INIT(&ddomain.guests);
@@ -4677,6 +4683,33 @@ int libxl_device_events_handler(libxl_ctx *ctx,
                                     be_path);
     if (rc) goto out;
 
+    kinds = libxl__xs_directory(gc, XBT_NULL, be_path, &nkinds);
+    if (kinds) {
+        for (i = 0; i < nkinds; i++) {
+            domains = libxl__xs_directory(gc, XBT_NULL,
+                    GCSPRINTF("%s/%s", be_path, kinds[i]), &ndomains);
+            if (!domains)
+                continue;
+            for (j = 0; j < ndomains; j++) {
+                devs = libxl__xs_directory(gc, XBT_NULL,
+                        GCSPRINTF("%s/%s/%s", be_path, kinds[i], domains[j]), &ndevs);
+                if (!devs)
+                    continue;
+                for (k = 0; k < ndevs; k++) {
+                    state_path = GCSPRINTF("%s/%s/%s/%s/state",
+                            be_path, kinds[i], domains[j], devs[k]);
+                    rc = libxl__xs_read_checked(gc, XBT_NULL, state_path, &sstate);
+                    if (rc || !sstate)
+                        continue;
+                    state = atoi(sstate);
+                    if (state == XenbusStateInitWait)
+                        backend_watch_callback(egc, &ddomain.watch,
+                                               be_path, state_path);
+                }
+            }
+        }
+    }
+
     return AO_INPROGRESS;
 
 out: