Re: [Qemu-devel] [PATCH 2/2] virtio-balloon: resume collecting stats on vmload

[Michael S. Tsirkin]

On Mon, Sep 05, 2016 at 11:02:36AM +0300, Roman Kagan wrote:
> On Sat, Sep 03, 2016 at 01:53:53AM +0300, Michael S. Tsirkin wrote:
> > On Fri, Sep 02, 2016 at 10:21:58AM +0300, Roman Kagan wrote:
> > > On Thu, Sep 01, 2016 at 10:26:54PM +0300, Michael S. Tsirkin wrote:
> > > > I'm sorry - I don't like this patch. This means that
> > > > virtio_balloon_receive_stats will be called and will poke
> > > > at the ring even if the ring was never kicked.
> > > 
> > > I'm not sure I understand what the problem is with that:
> > > virtio_balloon_receive_stats just returns early if virtio_queue_empty(),
> > > which is no more poking at the ring than is already done in virtio_load.
> > 
> > Generally we should not look at ring until there was a kick.
> 
> How else would you recover ->inuse?
> 
> Roman.

We seem to do this:
+            vdev->vq[i].inuse = vdev->vq[i].last_avail_idx -
+                                vdev->vq[i].used_idx;

Is this wrong?

-- 
MST