Re: [Qemu-devel] [PATCH 0/2] USB CCID device

[Anthony Liguori]

On 10/07/2010 02:39 AM, Alon Levy wrote:
> ----- "Anthony Liguori"<address@hidden>  wrote:
>
>    
> > On 10/06/2010 03:55 AM, Gerd Hoffmann wrote:
> >      
> > > On 10/06/10 02:28, Alon Levy wrote:
> > >        
> > > >          
> > > > > Does this work with live migration?  I can't see how it would.
> > > > >
> > > > >            
> > > > No, it doesn't right now. It would require cooperation with the
> > > >          
> > client,
> >      
> > > > to tell it to reconnect to the target qemu (kind of like spice).
> > > >          
> > > I think until we have this migration should have pretty much the
> > >        
> > same
> >      
> > > effect as a chardev disconnect, i.e. detach the usb device (which
> > >        
> > the
> >      
> > > guest will see as unplug).
> > >        
> > Better yet, mark the guest as unmigrateable and let the management
> > tool
> > unplug the usb device before migration and replug it after migration.
> >
> > It's the same principle behind device assignment.
> >
> >      
> Is there any way to also get a pre_migrate callback with 
> register_device_unmigratable?
> I'd like to send a VSC_Reconnect message, then the guest sees an unplug, then 
> migration,
>    

No.  The disconnect needs to happen in the management tooling layer.   
Same is true for any device doing hardware passthrough.

Automagic unplugging/plugging during migration is not a good idea 
universally so it's something that needs to happen as a policy at the 
management level.

Regards,

Anthony Liguori

> then (no plug yet since the device is marked as auto_attach=0) client reconnects
> (actually this happens before but to a paused machine waiting for migration), 
> and then
> causes attachement, same as a new machine.
>
>    
> > Regards,
> >
> > Anthony Liguori
> >
> >      
> > > Needs some code though, at minimum you'll have to xfer the connected
> > >        
> >      
> > > state from the migration source and have some bits in post_load()
> > > which do attach/detach if needed.
> > >
> > > cheers,
> > >    Gerd
> > >
> > >