* Peter Maydell (peter.mayd...@linaro.org) wrote: > On Fri, 3 Jul 2020 at 21:19, Philippe Mathieu-Daudé <f4...@amsat.org> wrote: > > > > Introduce a special state to indicate when an object doesn't > > have anything in its state to migrate. > > > > Suggested-by: Peter Maydell <peter.mayd...@linaro.org> > > Signed-off-by: Philippe Mathieu-Daudé <f4...@amsat.org> > > --- > > include/migration/vmstate.h | 1 + > > migration/vmstate.c | 7 +++++++ > > 2 files changed, 8 insertions(+) > > > > diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h > > index af7d80cd4e..0922bc8efa 100644 > > --- a/include/migration/vmstate.h > > +++ b/include/migration/vmstate.h > > @@ -195,6 +195,7 @@ struct VMStateDescription { > > }; > > > > extern const VMStateDescription vmstate_dummy; /* Exclusively for > > linux-user */ > > +extern const VMStateDescription vmstate_no_state_to_migrate; > > > > extern const VMStateInfo vmstate_info_bool; > > > > diff --git a/migration/vmstate.c b/migration/vmstate.c > > index bafa890384..d640cafad3 100644 > > --- a/migration/vmstate.c > > +++ b/migration/vmstate.c > > @@ -20,6 +20,13 @@ > > #include "trace.h" > > #include "qjson.h" > > > > +const VMStateDescription vmstate_no_state_to_migrate = { > > + .name = "empty-state", > > + .fields = (VMStateField[]) { > > + VMSTATE_END_OF_LIST() > > + } > > +}; > > Does this definitely not put any data into the migration stream? > We don't want to change what's on the wire for machines that > use devices that start using this. (If it does by default, it > would be easy to make the migration code special case the > magic symbol to act like "no vmsd specified").
I'd need to test it to be sure, but I think if we added a .needed to vmstate_no_state_to_migrate with a function that always returned false, then I think the stream would stay unchanged. Dave > thanks > -- PMM > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK