> On Thu, Jun 30, 2016 at 9:31 AM, Liang Li <liang.z...@intel.com> wrote:
> > After live migration, 'guest-stats' can't get the expected memory
> > status in the guest. This issue is caused by commit 4eae2a657d.
> > The value of 's->stats_vq_elem' will be NULL after live migration, and
> > the check in the function 'balloon_stats_poll_cb()' will prevent the
> > 'virtio_notify()' from executing. So guest will not update the memory
> > status.
> >
> > Signed-off-by: Liang Li <liang.z...@intel.com>
> > Cc: Michael S. Tsirkin <m...@redhat.com>
> > Cc: Ladi Prosek <lpro...@redhat.com>
> > Cc: Paolo Bonzini <pbonz...@redhat.com>
> > ---
> > hw/virtio/virtio-balloon.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> > index 557d3f9..cc6947f 100644
> > --- a/hw/virtio/virtio-balloon.c
> > +++ b/hw/virtio/virtio-balloon.c
> > @@ -98,13 +98,19 @@ static void balloon_stats_poll_cb(void *opaque) {
> > VirtIOBalloon *s = opaque;
> > VirtIODevice *vdev = VIRTIO_DEVICE(s);
> > + VirtQueueElement elem = {0};
> >
> > - if (s->stats_vq_elem == NULL || !balloon_stats_supported(s)) {
> > + if (!balloon_stats_supported(s)) {
> > /* re-schedule */
> > balloon_stats_change_timer(s, s->stats_poll_interval);
> > return;
> > }
> >
> > + if (s->stats_vq_elem == NULL) {
> > + virtqueue_push(s->svq, &elem, 0);
> > + virtio_notify(vdev, s->svq);
> > + return;
> > + }
>
> What if we are not in the just-after-live-migration situation though?
> If the guest simply didn't add a buffer to the queue for some reason,
> wouldn't this newly added push/notify break the balloon protocol?
>
Could you elaborate how it happens?
The added code only works for the situation just after live migration. right?
Thanks!
Liang
