balloon: Do not save VM state wrt asynchronous virtio operations

When working with the VM state (for loadvm/savevm and migration), it is not
valid to load and store pointers since the validity of those pointers cannot be
assured in the new qemu address space.  Therefore, virtio_balloon_save() and
virtio_balloon_load() must not handle the stats-related fields in struct
VirtIOBalloon.

If a memory stats request is in-flight at the time of a migration or savevm,
the request will not complete and should be resubmitted once migration or
loadvm completes.  Note that this extremely small race window can only be
triggered using QMP so it is not possible to hang the user monitor.

Signed-off-by: Adam Litke <agl@us.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
index 086d9d1ecdb4121b5f6eeb69e3c29411c182f314..6d120247fe42d1a139e3caff050435080fb87fb9 100644 (file)
--- a/hw/virtio-balloon.c
+++ b/hw/virtio-balloon.c
@@ -261,10 +261,6 @@ static void virtio_balloon_save(QEMUFile *f, void *opaque)
 
     qemu_put_be32(f, s->num_pages);
     qemu_put_be32(f, s->actual);
-    qemu_put_buffer(f, (uint8_t *)&s->stats_vq_elem, sizeof(VirtQueueElement));
-    qemu_put_buffer(f, (uint8_t *)&s->stats_vq_offset, sizeof(size_t));
-    qemu_put_buffer(f, (uint8_t *)&s->stats_callback, sizeof(MonitorCompletion));
-    qemu_put_buffer(f, (uint8_t *)&s->stats_opaque_callback_data, sizeof(void));
 }
 
 static int virtio_balloon_load(QEMUFile *f, void *opaque, int version_id)
@@ -278,11 +274,6 @@ static int virtio_balloon_load(QEMUFile *f, void *opaque, int version_id)
 
     s->num_pages = qemu_get_be32(f);
     s->actual = qemu_get_be32(f);
-    qemu_get_buffer(f, (uint8_t *)&s->stats_vq_elem, sizeof(VirtQueueElement));
-    qemu_get_buffer(f, (uint8_t *)&s->stats_vq_offset, sizeof(size_t));
-    qemu_get_buffer(f, (uint8_t *)&s->stats_callback, sizeof(MonitorCompletion));
-    qemu_get_buffer(f, (uint8_t *)&s->stats_opaque_callback_data, sizeof(void));
-
     return 0;
 }