Re: [Qemu-devel] [PATCH 20/30] s390x: convert virtio-ccw to hotplug handler API

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

On Thu, 25 Sep 2014 15:11:10 +0200
Igor Mammedov <imammedo@redhat.com> wrote:

> On Thu, 25 Sep 2014 13:08:38 +0200
> Cornelia Huck <cornelia.huck@de.ibm.com> wrote:

> > So, to summarize, what happened before was
> > 
> > bridge device              <--- (simple unplug invoked for dev)
> simple unplug should not exits for above device

Yes. I'm not sure why it does.

> 
> >  -> virtual bus
> >   -> virtio proxy device   <--- virtio unplug invoked for dev
> 
> >    -> virtio bus
> >     -> virtio device
> > 
> > which your patch changed to
> > 
> > bridge device
> >  -> virtual bus            <--- simple unplug invoked for virtio proxy dev
> >   -> virtio proxy device
> >    -> virtio bus           <--- (virtio unplug invoked for virtio dev)
> >     -> virtio device
> > 
> > Am I understanding this correctly?
> Let's try other way around:
> 
> bridge device (virtual_css_bridge) - non hotpluggable sysbus device
>   -> virtual bus (VIRTUAL_CSS_BUS)
>    -> virtio proxy device |
>     -> virtio bus         |- virtio_ccw_device_foo composite device managed with
>      -> virtio device     |  device_add/del command
> 
> internal "virtio device" is the only child of "virtio bus" and it's not supposed
> to be managed via device_add/del.

This makes sense; I'm wondering why virtio-bus had allow_hotplug set
before, though.

> 
> So to unplug "virtio proxy device" we should call virtio_ccw_busdev_unplug
> stored in "bridge device" with "virtual bus" using bridge as hotplug-handler.
> 
> does following patch work for you?

It does react as expected with a simple device_add/device_del (your
patches applied up to patch 19 with this one on top).