Hi On Sun, Dec 1, 2019 at 9:18 PM Peter Maydell <peter.mayd...@linaro.org> wrote: > > On Sun, 1 Dec 2019 at 10:19, Marc-André Lureau > <marcandre.lur...@gmail.com> wrote: > > > > - "serial: register vmsd with DeviceClass" > > > > This is standard qdev-ification, however it breaks backward migration, > > but that's just how qdev_set_legacy_instance_id() works. > > I don't understand this part. Surely the whole point > of setting a legacy instance ID is exactly to preserve > migration compatibility? If it doesn't do that then what > does setting legacy ID value do? >
It works in old->new direction only, because new code can match the legacy instance id. But when going from new->old, the legacy instance id is lost, as it uses new 0-based instance_id. This is just the way we have done so far, but I wish to be corrected if I am wrong. See the commit description for a bit more details. -- Marc-André Lureau
