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

[Anthony Liguori <anthony@codemonkey.ws>]

On 10/07/2010 02:39 AM, Alon Levy wrote:
> ----- "Anthony Liguori"<anthony@codemonkey.ws>  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
>>>
>>>