Subject: don't register shutdown watch and suspend event channel for Dom0

This pointlessly consumes resources and poses the risk of either
getting triggered inadvertently.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- a/drivers/xen/core/reboot.c
+++ b/drivers/xen/core/reboot.c
@@ -280,6 +280,15 @@ static int setup_shutdown_watcher(void)
 {
 	int err;
 
+	err = register_xenbus_watch(&sysrq_watch);
+	if (err) {
+		printk(KERN_ERR "Failed to set sysrq watcher\n");
+		return err;
+	}
+
+	if (is_initial_xendomain())
+		return 0;
+
 	xenbus_scanf(XBT_NIL, "control",
 		     "platform-feature-multiprocessor-suspend",
 		     "%d", &fast_suspend);
@@ -290,12 +299,6 @@ static int setup_shutdown_watcher(void)
 		return err;
 	}
 
-	err = register_xenbus_watch(&sysrq_watch);
-	if (err) {
-		printk(KERN_ERR "Failed to set sysrq watcher\n");
-		return err;
-	}
-
 	/* suspend event channel */
 	err = setup_suspend_evtchn();
 	if (err) {