virtio-balloon: Separate status handling into separate function

Separate out the code to retrieve balloon info from the code that sets
balloon values.

This will be used to separate the two callbacks from balloon.c and help
cope with 'balloon 0' on the monitor.  Currently, 'balloon 0' causes a
segfault in monitor_resume().

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 31 insertions, 20 deletions

diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
index 70a871034..2f371f2f6 100644
--- a/hw/virtio-balloon.c
+++ b/hw/virtio-balloon.c
@@ -199,36 +199,47 @@ static uint32_t virtio_balloon_get_features(VirtIODevice *vdev, uint32_t f)
     return f;
 }
 
+static void virtio_balloon_stat(void *opaque, MonitorCompletion cb,
+                                void *cb_data)
+{
+    VirtIOBalloon *dev = opaque;
+
+    /* For now, only allow one request at a time.  This restriction can be
+     * removed later by queueing callback and data pairs.
+     */
+    if (dev->stats_callback != NULL) {
+        return;
+    }
+    dev->stats_callback = cb;
+    dev->stats_opaque_callback_data = cb_data;
+
+    if (ENABLE_GUEST_STATS
+        && (dev->vdev.guest_features & (1 << VIRTIO_BALLOON_F_STATS_VQ))) {
+        virtqueue_push(dev->svq, &dev->stats_vq_elem, dev->stats_vq_offset);
+        virtio_notify(&dev->vdev, dev->svq);
+        return;
+    }
+
+    /* Stats are not supported.  Clear out any stale values that might
+     * have been set by a more featureful guest kernel.
+     */
+    reset_stats(dev);
+    complete_stats_request(dev);
+}
+
 static void virtio_balloon_to_target(void *opaque, ram_addr_t target,
                                      MonitorCompletion cb, void *cb_data)
 {
     VirtIOBalloon *dev = opaque;
 
-    if (target > ram_size)
+    if (target > ram_size) {
         target = ram_size;
-
+    }
     if (target) {
         dev->num_pages = (ram_size - target) >> VIRTIO_BALLOON_PFN_SHIFT;
         virtio_notify_config(&dev->vdev);
     } else {
-        /* For now, only allow one request at a time.  This restriction can be
-         * removed later by queueing callback and data pairs.
-         */
-        if (dev->stats_callback != NULL) {
-            return;
-        }
-        dev->stats_callback = cb;
-        dev->stats_opaque_callback_data = cb_data; 
-        if (ENABLE_GUEST_STATS && (dev->vdev.guest_features & (1 << VIRTIO_BALLOON_F_STATS_VQ))) {
-            virtqueue_push(dev->svq, &dev->stats_vq_elem, dev->stats_vq_offset);
-            virtio_notify(&dev->vdev, dev->svq);
-        } else {
-            /* Stats are not supported.  Clear out any stale values that might
-             * have been set by a more featureful guest kernel.
-             */
-            reset_stats(dev);
-            complete_stats_request(dev);
-        }
+        virtio_balloon_stat(opaque, cb, cb_data);
     }
 }