2 files changed, 15 insertions, 10 deletions

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 50dcb68d8070..ab609255a0f3 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -780,6 +780,9 @@ static int __init balloon_init(void)
         }
 #endif
 
+        /* Init the xen-balloon driver. */
+        xen_balloon_init();
+
         return 0;
 }
 subsys_initcall(balloon_init);
diff --git a/drivers/xen/xen-balloon.c b/drivers/xen/xen-balloon.c
index e7715cb62eef..e89136ab851e 100644
--- a/drivers/xen/xen-balloon.c
+++ b/drivers/xen/xen-balloon.c
@@ -59,6 +59,8 @@ static void watch_target(struct xenbus_watch *watch,
 {
         unsigned long long new_target;
         int err;
+        static bool watch_fired;
+        static long target_diff;
 
         err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
         if (err != 1) {
@@ -69,7 +71,14 @@ static void watch_target(struct xenbus_watch *watch,
         /* The given memory/target value is in KiB, so it needs converting to
          * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
          */
-        balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
+        new_target >>= PAGE_SHIFT - 10;
+        if (watch_fired) {
+                balloon_set_new_target(new_target - target_diff);
+                return;
+        }
+
+        watch_fired = true;
+        target_diff = new_target - balloon_stats.target_pages;
 }
 static struct xenbus_watch target_watch = {
         .node = "memory/target",
@@ -94,22 +103,15 @@ static struct notifier_block xenstore_notifier = {
         .notifier_call = balloon_init_watcher,
 };
 
-static int __init balloon_init(void)
+void xen_balloon_init(void)
 {
-        if (!xen_domain())
-                return -ENODEV;
-
-        pr_info("Initialising balloon driver\n");
-
         register_balloon(&balloon_dev);
 
         register_xen_selfballooning(&balloon_dev);
 
         register_xenstore_notifier(&xenstore_notifier);
-
-        return 0;
 }
-subsys_initcall(balloon_init);
+EXPORT_SYMBOL_GPL(xen_balloon_init);
 
 #define BALLOON_SHOW(name, format, args...)                             \
         static ssize_t show_##name(struct device *dev,                  \