Re: [Qemu-devel] [PATCH v2 00/12] virtio: fix virtio child recount in transports

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Tue, 30 Sep 2014 14:10:26 +0800
<arei.gonglei@huawei.com> wrote:

> From: Gonglei <arei.gonglei@huawei.com>
> 
> virtio-$device-{pci, s390, ccw} all duplicate the
> qdev properties of their virtio child. This approach does
> not work well with string or pointer properties since we
> must be careful about leaking or double-freeing them.
> 
> Use the QOM alias property to forward property accesses to the
> VirtIORNG child.  This way no duplication is necessary.

VirtIO$devtype?

> 
> For their child, 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-$device child is not finalized!
> 
> Drop our reference after the child property has been added to the
> parent.
> 
> Changs since v1:
>  - add the same handling for virtio-9p-pci device in PATCH 10 and PATCH 11.
>  - add a wrapper function for better code sharing 
>    in PATCH 12 (Cornelia/Michael/Paolo)

This patchset, applied on current master, survives some light testing
for s390-virtio and virtio-ccw (booting Linux, device_add/device_del
for the various device types).