Re: [Qemu-devel] [PATCH v11 14/15] rdma: introduce MIG_STATE_NONE and change MIG_STATE_SETUP state transition

["Michael R. Hines" <mrhines@linux.vnet.ibm.com>]

On 06/25/2013 05:49 AM, Juan Quintela wrote:
> mrhines@linux.vnet.ibm.com wrote:
>> From: "Michael R. Hines" <mrhines@us.ibm.com>
>>
>> As described in the previous patch, until now, the MIG_STATE_SETUP
>> state was not really a 'formal' state. It has been used as a 'zero' state
>> (what we're calling 'NONE' here) and QEMU has been unconditionally transitioning
>> into this state when the QMP migration command was called. Instead we want to
>> introduce MIG_STATE_NONE, which is our starting state in the state machine, and
>> then immediately transition into the MIG_STATE_SETUP state when the QMP migrate
>> command is issued.
>>
>> In order to do this, we must delay the transition into MIG_STATE_ACTIVE until
>> later in the migration_thread(). This is done to be able to timestamp the amount of
>> time spent in the SETUP state for proper accounting to the user during
>> an RDMA migration.
>>
>> Furthermore, the management software, until now, has never been aware of the
>> existence of the SETUP state whatsoever. This must change, because, timing of this
>> state implies that the state actually exists.
>>
>> These two patches cannot be separated because the 'query_migrate' QMP
>> switch statement needs to know how to handle this new state transition.
>>
>> Tested-by: Michael R. Hines <mrhines@us.ibm.com>
>> Signed-off-by: Michael R. Hines <mrhines@us.ibm.com>
>> @@ -316,6 +321,7 @@ static void migrate_fd_cancel(MigrationState *s)
>>   {
>>       DPRINTF("cancelling migration\n");
>>   
>> +    migrate_set_state(s, MIG_STATE_SETUP, MIG_STATE_CANCELLED);
>>       migrate_set_state(s, MIG_STATE_ACTIVE, MIG_STATE_CANCELLED);
>>   }
> This chunk is wrong.
>
> we can call qme_migrate_cancel() at any point,  and it is going to be
> called normally from MIG_STATE_ACTIVE.
>
>
>      migrate_set_satet(s, s->state,  MIG_STATE_CANCELLED)
>
> should do the trick.  Or something like that,  what do you think?
>
> Later,  Juan.
>
>
>

Great idea, thank you.

- Michael