Hi,
> Subject: Re: [Qemu-devel] [PATCH] virtio-pci: fix virtio-net child refcount in
> transports
>
> On Thu, Sep 04, 2014 at 07:41:32PM +0800, arei.gong...@huawei.com wrote:
> > From: Gonglei <arei.gong...@huawei.com>
> >
> > object_initialize() leaves the object with a refcount of 1.
> > object_property_add_child() adds its own reference which is dropped
> > again when the property is deleted.
> >
> > The upshot of this is that we always have a refcount >= 1. Upon hot
> > unplug the virtio-net child is not finalized!
> >
> > Drop our reference after the child property has been added to the
> > parent.
> >
> > Signed-off-by: Gonglei <arei.gong...@huawei.com>
> > ---
> > Stefan had post virtio-blk in commit c5d49db4, but virtio-net has
> > the same problem. Maybe the other virtio devices have too.
> > ---
> > hw/virtio/virtio-pci.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index ddb5da1..78dcd68 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -1456,6 +1456,7 @@ static void virtio_net_pci_instance_init(Object
> *obj)
> > VirtIONetPCI *dev = VIRTIO_NET_PCI(obj);
> > object_initialize(&dev->vdev, sizeof(dev->vdev), TYPE_VIRTIO_NET);
> > object_property_add_child(obj, "virtio-backend", OBJECT(&dev->vdev),
> NULL);
> > + object_unref(OBJECT(&dev->vdev));
> > }
> >
> > static const TypeInfo virtio_net_pci_info = {
>
> You just copied my commit but didn't consider all the work I did before
> to make virtio-blk safe. Similar work is necessary for virtio-net.
>
> Before it is okay to finalize the virtio-net (dev->vdev) object,
Sorry? In my case the virtio-net object will not be finalized at present
because its obj->ref is non-1 when we hot-unplug a virtio-net-pci device.
> you need to audit virtio-pci and virtio-net to make sure all resources and
> qdev properties are freed once and only once.
>
Yes, indeed.
> In the case of virtio-net, the qdev properties are duplicated so both
> virtio-net-pci and virtio-net point qdev properties at the same fields
> in virtio-net. For example, the "tx" string property will be
> double-freed with your patch.
>
OK. Got it!
> You can use the alias properties that I introduced to avoid duplicating
> qdev properties for virtio-net.
>
> Stefan
OK, Thanks for your point and suggestion! I will rework it more carefully
next week.
Best regards,
-Gonglei
