On Thu, Nov 03, 2022 at 10:04:54PM +0530, manish.mishra wrote: > > On 03/11/22 2:59 pm, Daniel P. Berrangé wrote: > > On Thu, Nov 03, 2022 at 02:50:25PM +0530, manish.mishra wrote: > > > On 01/11/22 9:15 pm, Daniel P. Berrangé wrote: > > > > On Tue, Nov 01, 2022 at 09:10:14PM +0530, manish.mishra wrote: > > > > > On 01/11/22 8:21 pm, Daniel P. Berrangé wrote: > > > > > > On Tue, Nov 01, 2022 at 02:30:29PM +0000, manish.mishra wrote: > > > > > > > diff --git a/migration/migration.c b/migration/migration.c > > > > > > > index 739bb683f3..f4b6f278a9 100644 > > > > > > > --- a/migration/migration.c > > > > > > > +++ b/migration/migration.c > > > > > > > @@ -733,31 +733,40 @@ void > > > > > > > migration_ioc_process_incoming(QIOChannel *ioc, Error **errp) > > > > > > > { > > > > > > > MigrationIncomingState *mis = > > > > > > > migration_incoming_get_current(); > > > > > > > Error *local_err = NULL; > > > > > > > - bool start_migration; > > > > > > > QEMUFile *f; > > > > > > > + bool default_channel = true; > > > > > > > + uint32_t channel_magic = 0; > > > > > > > + int ret = 0; > > > > > > > - if (!mis->from_src_file) { > > > > > > > - /* The first connection (multifd may have multiple) */ > > > > > > > + if (migrate_use_multifd() && !migration_in_postcopy()) { > > > > > > > + ret = qio_channel_read_peek_all(ioc, (void > > > > > > > *)&channel_magic, > > > > > > > + sizeof(channel_magic), > > > > > > > &local_err); > > > > > > > + > > > > > > > + if (ret != 1) { > > > > > > > + error_propagate(errp, local_err); > > > > > > > + return; > > > > > > > + } > > > > > > ....and thus this will fail for TLS channels AFAICT. > > > > > Yes, thanks for quick review Daniel. You pointed this earlier too, > > > > > sorry missed it, will put another check !migrate_use_tls() in V2. > > > > But we need this problem fixed with TLS too, so just excluding it > > > > isn't right. IMHO we need to modify the migration code so we can > > > > read the magic earlier, instead of peeking. > > > > > > > > > > > > With regards, > > > > Daniel > > > Hi Daniel, I was trying tls migrations. What i see is that tls session > > > creation does handshake. So if we read ahead in ioc_process_incoming > > > for default channel. Because client sends magic only after multiFD > > > channels are setup, which too requires tls handshake. > > By the time we get to migrate_ioc_process_incoming, the TLS handshake > > has already been performed. > > > > migration_channel_process_incoming > > -> migration_ioc_process_incoming > > > > vs > > > > migration_channel_process_incoming > > -> migration_tls_channel_process_incoming > > -> migration_tls_incoming_handshake > > -> migration_channel_process_incoming > > -> migration_ioc_process_incoming > > > > Yes sorry i thought we block on source side till handshake is done but that > is not true. I checked then why that deadlock is happening. So this where the > dealock is happening. > > static int ram_save_setup(QEMUFile *f, void *opaque) { > + > + > ram_control_before_iterate(f, RAM_CONTROL_SETUP); > ram_control_after_iterate(f, RAM_CONTROL_SETUP); > > ret = multifd_send_sync_main(f); > if (ret < 0) { > return ret; > } > > qemu_put_be64(f, RAM_SAVE_FLAG_EOS); > qemu_fflush(f); > > return 0; > } > > Now if we block in migration_ioc_process_incoming for reading magic > value from channel, which is actually sent by client when this > qemu_fflush is done. Before this qemu_fflush we wait for > multifd_send_sync_main which actually requires that tls handshake is > done for multiFD channels as it blocks on sem_sync which posted by > multifd_send_thread which is called after handshake||. But then on > destination side we are blocked in migration_ioc_process_incoming() > waiting to read something from default channel hence handshake for > multiFD channels can not happen. This to me looks unresolvable > whatever way we try to manipulate stream until we do some changes > on source side.
The TLS handshake is already complete when migration_ioc_process_incoming is blocking on read. Regardless of which channel we're talking about, thue TLS handshake is always performed & finished before we try to either send or recv any data. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|