Re: [Qemu-devel] [PATCH 2/3] move vm stop/start to migrate_set_state

[Anthony Liguori <anthony@codemonkey.ws>]

Paolo Bonzini wrote:
> With this patch, the state machine grows a new state, COMPLETING.
> This new state corresponds to the VM being stopped while migration
> is finalized.  Stopping and starting the machine is driven
> exclusively by the state machine mechanisms.
>
> Two rare bugs are fixed.  The first is a race; the VM used to remain
> stopped if a migration was canceled exactly in what corresponds
> to the new COMPLETING state.

You cannot cancel during the stopped state.  When you enter into the 
final stage, you no longer process monitor input.

>   A bit worse is that if an error occurred
> exactly during the final stage (for example due to disk full)
> the VM was unconditionally restarted, even if it was paused before
> the beginning of the migration.
>   

How does the disk become full during the final stage?  The guest isn't 
running.

Regards,

Anthony Liguori