Re: [Qemu-devel] [PULL 29/57] migrate_start_postcopy: Command to trigger transition to postcopy

[Eric Blake <eblake@redhat.com>]

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[adding Markus for a qapi question]

On 11/09/2015 10:28 AM, Juan Quintela wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Once postcopy is enabled (with migrate_set_capability), the migration
> will still start on precopy mode.  To cause a transition into postcopy
> the:
> 
>   migrate_start_postcopy
> 
> command must be issued.  Postcopy will start sometime after this
> (when it's next checked in the migration loop).
> 
> Issuing the command before migration has started will error,
> and issuing after it has finished is ignored.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> Reviewed-by: Juan Quintela <quintela@redhat.com>
> Reviewed-by: Amit Shah <amit.shah@redhat.com>
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---

I know I reviewed an earlier version of this patch, but that was
probably before 24/57 of this pull request spelled the migration
capability bit as x-postcopy-ram.

> +++ b/qapi-schema.json
> @@ -702,6 +702,14 @@
>              '*tls-port': 'int', '*cert-subject': 'str' } }
> 
>  ##
> +# @migrate-start-postcopy
> +#
> +# Switch migration to postcopy mode

No documentation on the relation to the [x-]postcopy-ram capability bit?
 Will this command always fail if that bit is not set?

> +#
> +# Since: 2.5
> +{ 'command': 'migrate-start-postcopy' }

Should we rename this command to 'x-migrate-start-postcopy' until we are
ready to rename the entire feature to the stable namespace?

If so, I'm okay with that as a followup patch (so as not to delay the
pull request), but we should really make up our minds what 2.5 will
provide on this front.


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


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