Re: [Qemu-devel] [PATCH] migration: Introduce MIGRATION_STATUS_FINISHING

[Eric Blake]

On 10/26/2015 06:47 AM, Pavel Fedin wrote:
> This status is set after vm_stop_force_state(), and is telling us that all
> CPUs are stopped, and we are finishing up with the migration.
> 
> Also, call notifier_list_notify() when this status is set. This will be
> necessary for ITS live migration on ARM, which will have to dump its state
> into guest RAM at this point.
> 
> Signed-off-by: Pavel Fedin <address@hidden>
> ---

Interface review only:

> +++ b/qapi-schema.json
> @@ -430,6 +430,8 @@
>  #
>  # @active: in the process of doing migration.
>  #
> +# @finishing: migration is being finished, CPUs have been stopped.
> +#

Missing a '(since 2.5)' notation.  Also, adding new user-visible states
has a tendency to break existing clients that aren't prepared for
unexpected states (although technically such bugs are in the client - in
the past, libvirt used to be one such client, although we've tried to
fix it to gracefully ignore unknown states).  Are we sure no other
existing state works for this?  I'm not opposed to the addition, just
wanting to make sure we have good reason for it.

One design idea for adding new states is making sure the new state will
not be exposed unless the client specifies some new option to enable the
state, so that old clients will never see the state and new clients have
expressed their interest in the state by opting-in to it with the new
option.

>  # @completed: migration is finished.
>  #
>  # @failed: some error occurred during migration process.
> @@ -439,7 +441,7 @@
>  ##
>  { 'enum': 'MigrationStatus',
>    'data': [ 'none', 'setup', 'cancelling', 'cancelled',
> -            'active', 'completed', 'failed' ] }
> +            'active', 'finishing', 'completed', 'failed' ] }
>  
>  ##
>  # @MigrationInfo
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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