Re: [PATCH 1/2] virtio: reset region cache when on queue deletion

[Michael S. Tsirkin]

On Thu, Dec 26, 2019 at 11:29:50AM +0200, Yuri Benditovich wrote:
> On Thu, Dec 26, 2019 at 10:58 AM Jason Wang <address@hidden> wrote:
> >
> >
> > On 2019/12/26 下午12:36, Yuri Benditovich wrote:
> > > https://bugzilla.redhat.com/show_bug.cgi?id=1708480
> > > Fix leak of region reference that prevents complete
> > > device deletion on hot unplug.
> >
> >
> > More information is needed here, the bug said only q35 can meet this
> > issue. What makes q35 different here?
> >
> 
> I do not have any ready answer, I did not dig into it too much.
> Probably Michael Tsirkin or Paolo Bonzini can answer without digging.



> >
> > >
> > > Signed-off-by: Yuri Benditovich <address@hidden>
> > > ---
> > >   hw/virtio/virtio.c | 5 +++++
> > >   1 file changed, 5 insertions(+)
> > >
> > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > > index 04716b5f6c..baadec8abc 100644
> > > --- a/hw/virtio/virtio.c
> > > +++ b/hw/virtio/virtio.c
> > > @@ -2340,6 +2340,11 @@ void virtio_del_queue(VirtIODevice *vdev, int n)
> > >       vdev->vq[n].vring.num_default = 0;
> > >       vdev->vq[n].handle_output = NULL;
> > >       vdev->vq[n].handle_aio_output = NULL;
> > > +    /*
> > > +     * with vring.num = 0 the queue will be ignored
> > > +     * in later loops of region cache reset
> > > +     */
> >
> >
> > I can't get the meaning of this comment.
> >
> > Thanks
> >
> >
> > > +    virtio_virtqueue_reset_region_cache(&vdev->vq[n]);


Do we need to drop this from virtio_device_free_virtqueues then?

> > >       g_free(vdev->vq[n].used_elems);
> > >   }
> > >
> >