@@ -628,8 +628,13 @@ static void virtio_balloon_free_page_done(VirtIOBalloon *s)
{
VirtIODevice *vdev = VIRTIO_DEVICE(s);
- s->free_page_report_status = FREE_PAGE_REPORT_S_DONE;
- virtio_notify_config(vdev);
+ if (s->free_page_report_status != FREE_PAGE_REPORT_S_DONE) {
+ /* See virtio_balloon_free_page_stop() */
+ qemu_mutex_lock(&s->free_page_lock);
+ s->free_page_report_status = FREE_PAGE_REPORT_S_DONE;
+ qemu_mutex_unlock(&s->free_page_lock);
+ virtio_notify_config(vdev);
+ }
}
static int
@@ -653,8 +658,6 @@ virtio_balloon_free_page_report_notify(NotifierWithReturn *n, void *data)
case PRECOPY_NOTIFY_SETUP:
precopy_enable_free_page_optimization();
break;
- case PRECOPY_NOTIFY_COMPLETE:
- case PRECOPY_NOTIFY_CLEANUP:
case PRECOPY_NOTIFY_BEFORE_BITMAP_SYNC:
virtio_balloon_free_page_stop(dev);
break;
@@ -662,9 +665,22 @@ virtio_balloon_free_page_report_notify(NotifierWithReturn *n, void *data)
if (vdev->vm_running) {
virtio_balloon_free_page_start(dev);
} else {
+ /*
+ * Set S_DONE before migrating the vmstate, so the guest will reuse
+ * all hinted pages once running on the destination.
+ */
virtio_balloon_free_page_done(dev);
}
break;
+ case PRECOPY_NOTIFY_CLEANUP:
+ /*
+ * Especially, if something goes wrong during precopy or if migration
+ * is canceled, we have to properly communicate S_DONE to the VM.
+ */
+ virtio_balloon_free_page_done(dev);
+ break;
+ case PRECOPY_NOTIFY_COMPLETE:
+ break;
default:
virtio_error(vdev, "%s: %d reason unknown", __func__, pnd->reason);
}
If something goes wrong during precopy, before stopping the VM, we will never send a S_DONE indication to the VM, resulting in the hinted pages not getting released to be used by the guest OS (e.g., Linux). Easy to reproduce: 1. Start migration (e.g., HMP "migrate -d 'exec:gzip -c > STATEFILE.gz'") 2. Cancel migration (e.g., HMP "migrate_cancel") 3. Oberve in the guest (e.g., cat /proc/meminfo) that there is basically no free memory left. While at it, add similar locking to virtio_balloon_free_page_done() as done in virtio_balloon_free_page_stop. Locking is still weird, but that has to be sorted out separately. There is nothing to do in the PRECOPY_NOTIFY_COMPLETE case. Add some comments regarding S_DONE handling. Fixes: c13c4153f76d ("virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT") Cc: Wei Wang <wei.w.wang@intel.com> Cc: Alexander Duyck <alexander.duyck@gmail.com> Signed-off-by: David Hildenbrand <david@redhat.com> --- hw/virtio/virtio-balloon.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-)