Re: [RFC 4/6] migration: Deprecate -incoming <uri>

On 6/22/23 10:52, Juan Quintela wrote: > User friendliness. > The problem is that if you use more than two channels with multifd, on > the incoming side, you need to do: You're sacrificing user-friendliness for the 99.99% that don't use multifd, for an error (i.e. it's not even fixing the issue) for the 0.01% that use multifd. That's not user-friendly.

> - migrate_set_parameter multifd-channels 16 > - migrate_incoming <uri> > >> The issue is not how many features the command line has, but how >> they're implemented. > Or if they are confusing for the user? Anyone using multifd is not a typical user anyway.

>> If they're just QMP wrappers and as such they're self-contained in >> softmmu/vl.c, that's fine. >> >> In fact, even for parameters, we could use keyval to parse "-incoming" > What is keyval? util/keyval.c and include/qemu/keyval.h. It parses a list of key=value pairs into a QDict. Once you have removed the "source" key from the QDict you can use a visitor to parse the rest into a MigrateSetParameters. See the handling of QEMU_OPTION_audio, it could be something like case QEMU_OPTION_incoing: { Visitor *v; MigrateSetParameters *incoming_params = NULL; QDict *dict = keyval_parse(optarg, "source", NULL, &error_fatal); if (incoming) { if (qdict_haskey(dict, "source")) { error_setg(&error_fatal, "Parameter 'source' is duplicate"); } } else { if (!qdict_haskey(dict, "source")) { error_setg(&error_fatal, "Parameter 'source' is missing"); } runstate_set(RUN_STATE_INMIGRATE); incoming = g_strdup(qdict_get_str(dict, "source")); qdict_del(dict, "source"); } v = qobject_input_visitor_new_keyval(QOBJECT(dict)); qobject_unref(dict); visit_type_MigrateSetParameters(v, NULL, &incoming_params, &error_fatal); visit_free(v); qmp_migration_set_parameters(incoming_params, &error_fatal); qapi_free_MigrateSetParameters(incoming_params); } For example "-incoming [source=]tcp:foo,multifd-channels=16" would desugar to migrate_set_parameter multifd-channels 16 migrate_incoming tcp:foo The only incompatibility is for people who are using "," in an URI, which is rare and only an issue for the "exec" protocol.

Paolo >> and >> set the parameters in the same place as above. That would remove the need >> for "-global migration". > Could you elaborate? > The other option that I can think of is changing the error messages for > migrate_check_parameters() and give instructions that you can't set > multifd channels once that you have started incoming migration. > Explaining there to use migrate_incoming command? > Later, Juan. >