Re: [PATCH V2 04/11] migration: stop vm earlier for cpr

[Steven Sistare]

On 7/17/2024 2:59 PM, Fabiano Rosas wrote:
> Steve Sistare <steven.sistare@oracle.com> writes:
>
> > Stop the vm earlier for cpr, to guarantee consistent device state when
> > CPR state is saved.
> >
> > Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> > ---
> >   migration/migration.c | 22 +++++++++++++---------
> >   1 file changed, 13 insertions(+), 9 deletions(-)
> >
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 0f47765..8a8e927 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -2077,6 +2077,7 @@ void qmp_migrate(const char *uri, bool has_channels,
> >       MigrationState *s = migrate_get_current();
> >       g_autoptr(MigrationChannel) channel = NULL;
> >       MigrationAddress *addr = NULL;
> > +    bool stopped = false;
> >   
> >       /*
> >        * Having preliminary checks for uri and channel
> > @@ -2120,6 +2121,15 @@ void qmp_migrate(const char *uri, bool has_channels,
> >           }
> >       }
> >   
> > +    if (migrate_mode_is_cpr(s)) {
> > +        int ret = migration_stop_vm(s, RUN_STATE_FINISH_MIGRATE);
> > +        if (ret < 0) {
> > +            error_setg(&local_err, "migration_stop_vm failed, error %d", -ret);
> > +            goto out;
> > +        }
> > +        stopped = true;
> > +    }
> > +
> >       if (cpr_state_save(&local_err)) {
> >           goto out;
> >       }
> > @@ -2155,6 +2165,9 @@ out:
> >           }
> >           migrate_fd_error(s, local_err);
> >           error_propagate(errp, local_err);
> > +        if (stopped && runstate_is_live(s->vm_old_state)) {
> > +            vm_start();
> > +        }
>
> What about non-live states? Shouldn't this be:
>
> if (stopped) {
>     vm_resume();
> }

Not quite.  vm_old_state may be a stopped state, so we don't want to resume.
However, I should probably restore the old stopped state here.  I'll try some 
more
error recovery scenarios.

- Steve

> >           return;
> >       }
> >   }
> > @@ -3738,7 +3751,6 @@ void migrate_fd_connect(MigrationState *s, Error 
> > *error_in)
> >       Error *local_err = NULL;
> >       uint64_t rate_limit;
> >       bool resume = (s->state == MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP);
> > -    int ret;
> >   
> >       /*
> >        * If there's a previous error, free it and prepare for another one.
> > @@ -3810,14 +3822,6 @@ void migrate_fd_connect(MigrationState *s, Error 
> > *error_in)
> >           return;
> >       }
> >   
> > -    if (migrate_mode_is_cpr(s)) {
> > -        ret = migration_stop_vm(s, RUN_STATE_FINISH_MIGRATE);
> > -        if (ret < 0) {
> > -            error_setg(&local_err, "migration_stop_vm failed, error %d", -ret);
> > -            goto fail;
> > -        }
> > -    }
> > -
> >       if (migrate_background_snapshot()) {
> >           qemu_thread_create(&s->thread, "mig/snapshot",
> >                   bg_migration_thread, s, QEMU_THREAD_JOINABLE);