Re: [PATCH V1 1/3] migration: check mode in notifiers

[Peter Xu]

On Wed, Jan 10, 2024 at 01:08:01PM -0500, Steven Sistare wrote:
> On 1/10/2024 2:09 AM, Peter Xu wrote:
> > On Wed, Dec 13, 2023 at 10:11:31AM -0800, Steve Sistare wrote:
> >> The existing notifiers should only apply to normal mode.
> >>
> >> No functional change.
> > 
> > Instead of adding such check in every notifier, why not make CPR a separate
> > list of notifiers?  Just like the blocker lists.
> 
> Sure.   I proposed minimal changes in this current series, but extending the 
> api to take migration mode would be nicer.
> 
> > Aside of this patch, I just started to look at this "notifier" code, I
> > really don't think we should pass in MigrationState* into the notifiers.
> > IIUC we only need the "state" as an enum.  Then with two separate
> > registers, the device code knows the migration mode.
> > 
> > What do you think?
> 
> If we pass state, the notifier must either compare to enum values such as
> MIGRATION_STATUS_COMPLETED instead of calling migration_has_finished(s), or
> we must define new accessors such as migration_state_is_finished(state).
> 
> IMO passing MigrationState is the best approach.
> MigrationState is an incomplete type in most notifiers, and the client can
> pass it to a limited set of accessors to get more information -- exactly what 
> we want to hide migration internals.  However, we could further limit the
> allowed accessors, eg move these to a new file "include/migration/notifier.h".
> 
> ----------------------------------------
> #include "qemu/notify.h"
> void migration_add_notifier(Notifier *notify,
>                             void (*func)(Notifier *notifier, void *data));
> void migration_remove_notifier(Notifier *notify);
> bool migration_is_active(MigrationState *);
> bool migration_in_setup(MigrationState *);
> bool migration_has_finished(MigrationState *);
> bool migration_has_failed(MigrationState *);
> -----------------------------------------------

Yes this also sounds good.  Thanks,

-- 
Peter Xu