Peter Xu <[email protected]> writes: > This is the corresponding outgoing fix for the same problem mentioned in > the previous patch. > > The idea is simple: either migration to an old QEMU or when TLS is enabled, > we rely on correct ordering of channels to make it work: first main, then > multifd, finally preempt. > > This patch re-orders multifd and postcopy preempt channel on outgoing side, > but only for the old machine types where preempt_pre_7_2 set, to make it > follow the right orders to create the channels. > > Keep the resume path alone because the resume path never involve multifd > channels, even if multifd is enabled. For that, fun fact: when multifd is > enabled with postcopy preempt, network interruption will break all multifd > channels, but they're never re-connected, until they got recycled at the > end of postcopy migration. OTOH, multifd_recv_all_channels_created() > reports true even after postcopy network down, as multifd_recv_state->count > is never decremented. > > NOTE: this will move the preempt channel connection no matter multifd is > enabled or not. It should fix multifd's case, but should have zero impact > on when multifd is not enabled. > > Fixes: e27418861288 ("migration: enable multifd and postcopy together") > Signed-off-by: Peter Xu <[email protected]> > --- > migration/migration.c | 33 ++++++++++++++++++++++++--------- > 1 file changed, 24 insertions(+), 9 deletions(-) > > diff --git a/migration/migration.c b/migration/migration.c > index b140fb6950..53cb6d3821 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -3729,6 +3729,21 @@ static void *migration_thread(void *opaque) > goto out; > } > > + /* > + * Only for old 7.1/7.2 machine types (preempt mode supported since > + * 7.1). Connect the preempt channel only after multifd channels, > + * because some QEMU versions (v10.1 to v11.1) will assume the order of > + * channels to be: (1) main, then (2) multifd channels, then (3) > + * preempt channel. IOW, (3) must be after (2). > + * > + * multifd_send_setup() makes sure all multifd channels be connected > + * first, then initiate preempt channel here guarantees the ordering to > + * those QEMU binaries. > + */ > + if (migrate_postcopy_preempt() && s->preempt_pre_7_2) { > + postcopy_preempt_setup(s); > + } > + > bql_lock(); > qemu_savevm_state_header(s->to_dst_file); > bql_unlock(); > @@ -4009,16 +4024,16 @@ void migration_start_outgoing(MigrationState *s) > open_return_path_on_source(s); > } > > - /* > - * This needs to be done before resuming a postcopy. Note: for newer > - * QEMUs we will delay the channel creation until postcopy_start(), to > - * avoid disorder of channel creations. > - */ > - if (migrate_postcopy_preempt() && s->preempt_pre_7_2) { > - postcopy_preempt_setup(s); > - } > - > if (resume) { > + /* > + * This needs to be done before resuming a postcopy. Note: for newer > + * QEMUs we will delay the channel creation until postcopy_start(), > to > + * avoid disorder of channel creations. > + */ > + if (migrate_postcopy_preempt() && s->preempt_pre_7_2) { > + postcopy_preempt_setup(s); > + } > + > /* Wakeup the main migration thread to do the recovery */ > migrate_set_state(&s->state, MIGRATION_STATUS_POSTCOPY_RECOVER_SETUP, > MIGRATION_STATUS_POSTCOPY_RECOVER);
Reviewed-by: Fabiano Rosas <[email protected]>
