Re: [PATCH 1/2] qapi/run-state: Add a new shutdown cause 'migration-completed'

[Kunkun Jiang]

Hi Daniel,

On 2021/7/5 20:48, Daniel P. Berrangé wrote:
> On Mon, Jul 05, 2021 at 08:36:52PM +0800, Kunkun Jiang wrote:
> > In the current version, the source QEMU process does not automatic
> > exit after a successful migration. Additional action is required,
> > such as sending { "execute": "quit" } or ctrl+c. For simplify, add
> > a new shutdown cause 'migration-completed' to exit the source QEMU
> > process after a successful migration.
> IIUC, 'STATUS_COMPLETED' state is entered on the source host
> once it has finished sending all VM state, and thus does not
> guarantee that the target host has successfully received and
> loaded all VM state.
Thanks for your reply.

If the target host doesn't successfully receive and load all VM state,
we can send { "execute": "cont" } to resume the soruce in time to
ensure that VM will not lost?
> Typically a mgmt app will need to directly confirm that the
> target host QEMU has succesfully started running, before it
> will tell the source QEMU to quit.
'a mgmt app', such as libvirt?

Thanks,
Kunkun Jiang
> So, AFAICT, this automatic exit after STATUS_COMPLETED is
> not safe and could lead to total loss of the running VM in
> error scenarios.
>
>
>
> > Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
> > ---
> >   migration/migration.c | 1 +
> >   qapi/run-state.json   | 4 +++-
> >   2 files changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 4228635d18..16782c93c2 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -3539,6 +3539,7 @@ static void migration_iteration_finish(MigrationState *s)
> >       case MIGRATION_STATUS_COMPLETED:
> >           migration_calculate_complete(s);
> >           runstate_set(RUN_STATE_POSTMIGRATE);
> > +        qemu_system_shutdown_request(SHUTDOWN_CAUSE_MIGRATION_COMPLETED);
> >           break;
> >   
> >       case MIGRATION_STATUS_ACTIVE:
> > diff --git a/qapi/run-state.json b/qapi/run-state.json
> > index 43d66d700f..66aaef4e2b 100644
> > --- a/qapi/run-state.json
> > +++ b/qapi/run-state.json
> > @@ -86,12 +86,14 @@
> >   #                   ignores --no-reboot. This is useful for sanitizing
> >   #                   hypercalls on s390 that are used during kexec/kdump/boot
> >   #
> > +# @migration-completed: Reaction to the successful migration
> > +#
> >   ##
> >   { 'enum': 'ShutdownCause',
> >     # Beware, shutdown_caused_by_guest() depends on enumeration order
> >     'data': [ 'none', 'host-error', 'host-qmp-quit', 'host-qmp-system-reset',
> >               'host-signal', 'host-ui', 'guest-shutdown', 'guest-reset',
> > -            'guest-panic', 'subsystem-reset'] }
> > +            'guest-panic', 'subsystem-reset', 'migration-completed'] }
> >   
> >   ##
> >   # @StatusInfo:
> > --
> > 2.23.0
> Regards,
> Daniel