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

[Igor Mammedov]

On Thu, 25 Sep 2014 16:32:37 +0200
Cornelia Huck <address@hidden> wrote:

> On Thu, 25 Sep 2014 15:11:10 +0200
> Igor Mammedov <address@hidden> wrote:
> 
> > On Thu, 25 Sep 2014 13:08:38 +0200
> > Cornelia Huck <address@hidden> 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.
it was due to behavior of bus_add_child() which required bus to be 
hotplugggable.

> 
> > 
> > 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).
Thanks for confirmation, I'll amend s390-virtio in similar manner for V2