> > > > Why don't we raise the error when we query the values?
You already raise an error here, so that works out of the box:
if (s->stats[i] == -1) {
error_setg(errp,
"timer hasn't been enabled or guest doesn't support '%s'", name);
> > >
> > > Hmm, that's a good idea.
> > >
> > > Only small nit is that, today old stats will remain available to be
> > > queried even if you disable the timer. If we do what you suggest,
> > > old stats won't be available if the module is unloaded (well, I
> > > *guess* the guest will unset the feature bit on module removal).
> >
> > What is the problem with that? It would be no problem to simulate the
> > old behavior, but why do you want that?
>
> I actually just thought that it's a nice to have.
The following patch seems to work for me:
Index: new/hw/virtio-balloon.c
===================================================================
--- new.orig/hw/virtio-balloon.c 2012-12-12 14:05:56.000000000 +0100
+++ new/hw/virtio-balloon.c 2012-12-12 14:07:43.000000000 +0100
@@ -111,6 +111,10 @@
{
VirtIOBalloon *s = opaque;
+ if (!balloon_stats_supported(s) || !runstate_is_running()) {
+ return;
+ }
+
virtqueue_push(s->svq, &s->stats_vq_elem, s->stats_vq_offset);
virtio_notify(&s->vdev, s->svq);
}
@@ -164,11 +168,6 @@
VirtIOBalloon *s = opaque;
int64_t value;
- if (!balloon_stats_supported(s)) {
- error_setg(errp, "guest doesn\'t support balloon stats");
- return;
- }
-
visit_type_int(v, &value, name, errp);
if (error_is_set(errp)) {
return;
