diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 1a5353a753fc..b2bb5aa3b054 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -489,8 +489,9 @@ static void xen_hvm_setup_cpu_clockevents(void)
 __init void xen_hvm_init_time_ops(void)
 {
 	/* vector callback is needed otherwise we cannot receive interrupts
-	 * on cpu > 0 */
-	if (!xen_have_vector_callback && num_present_cpus() > 1)
+	 * on cpu > 0 and at this point we don't know how many cpus are
+	 * available */
+	if (!xen_have_vector_callback)
 		return;
 	if (!xen_feature(XENFEAT_hvm_safe_pvclock)) {
 		printk(KERN_INFO "Xen doesn't support pvclock on HVM,"
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 29bac5118877..d409495876f1 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -755,7 +755,10 @@ int register_xenstore_notifier(struct notifier_block *nb)
 {
 	int ret = 0;
 
-	blocking_notifier_chain_register(&xenstore_chain, nb);
+	if (xenstored_ready > 0)
+		ret = nb->notifier_call(nb, 0, NULL);
+	else
+		blocking_notifier_chain_register(&xenstore_chain, nb);
 
 	return ret;
 }
@@ -769,7 +772,7 @@ EXPORT_SYMBOL_GPL(unregister_xenstore_notifier);
 
 void xenbus_probe(struct work_struct *unused)
 {
-	BUG_ON((xenstored_ready <= 0));
+	xenstored_ready = 1;
 
 	/* Enumerate devices in xenstore and watch for changes. */
 	xenbus_probe_devices(&xenbus_frontend);
@@ -835,8 +838,8 @@ static int __init xenbus_init(void)
 			xen_store_evtchn = xen_start_info->store_evtchn;
 			xen_store_mfn = xen_start_info->store_mfn;
 			xen_store_interface = mfn_to_virt(xen_store_mfn);
+			xenstored_ready = 1;
 		}
-		xenstored_ready = 1;
 	}
 
 	/* Initialize the interface to xenstore. */