Re: [PATCH v8 6/9] migration: New migrate and migrate-incoming argument 'channels'

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Jul 13, 2023 at 10:57:10AM +0000, Het Gala wrote:
> MigrateChannelList allows to connect accross multiple interfaces.
> Add MigrateChannelList struct as argument to migration QAPIs.
> 
> We plan to include multiple channels in future, to connnect
> multiple interfaces. Hence, we choose 'MigrateChannelList'
> as the new argument over 'MigrateChannel' to make migration
> QAPIs future proof.
> 
> For current series, limit the size of MigrateChannelList
> to single element (single interface) as runtime check.
> 
> Suggested-by: Aravind Retnakaran <aravind.retnakaran@nutanix.com>
> Signed-off-by: Het Gala <het.gala@nutanix.com>
> Acked-by: Markus Armbruster <armbru@redhat.com>
> ---
>  migration/migration-hmp-cmds.c |  16 +++--
>  migration/migration.c          |  34 ++++++++--
>  qapi/migration.json            | 109 ++++++++++++++++++++++++++++++++-
>  softmmu/vl.c                   |   2 +-
>  4 files changed, 147 insertions(+), 14 deletions(-)
> 
> diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c
> index 9885d7c9f7..5f04598202 100644
> --- a/migration/migration-hmp-cmds.c
> +++ b/migration/migration-hmp-cmds.c
> @@ -423,10 +423,12 @@ void hmp_migrate_incoming(Monitor *mon, const QDict *qdict)
>  {
>      Error *err = NULL;
>      const char *uri = qdict_get_str(qdict, "uri");
> +    MigrationChannelList *caps = NULL;
> +    g_autoptr(MigrationChannel) channel = g_new0(MigrationChannel, 1);
>  
> -    qmp_migrate_incoming(uri, &err);
> -
> -    hmp_handle_error(mon, err);
> +    QAPI_LIST_PREPEND(caps, channel);
> +    qmp_migrate_incoming(uri, false, caps, &err);
> +    qapi_free_MigrationChannelList(caps);

This is creating a single element channel list, but putting
no channel info in it, and passing false.

I think HMP ought to be doing

    MigrationAddress *addr = NULL;
    migrate_uri_parse(uri, &addr);

    channel->channel_type = ..MAIN...
    channel->address = addr;

And the calling

   qmp_migrate_incoming(NULL, true, caps, &err);


Except we can't do that in this patch, so qmp_migrate_incoming isn't
actually honouring the channel list yet, just doing the boilerplate
checks. So this patch should merely dlo

   qmp_migrate_incoming(uri, false, NULL, &err);

and the MigrateChannel additions here should be in a later patch.
Probably best to have the HMP conversion in its own dedicate pathc.

>  }
>  
>  void hmp_migrate_recover(Monitor *mon, const QDict *qdict)
> @@ -704,9 +706,13 @@ void hmp_migrate(Monitor *mon, const QDict *qdict)
>      bool resume = qdict_get_try_bool(qdict, "resume", false);
>      const char *uri = qdict_get_str(qdict, "uri");
>      Error *err = NULL;
> +    MigrationChannelList *caps = NULL;
> +    g_autoptr(MigrationChannel) channel = g_new0(MigrationChannel, 1);
>  
> -    qmp_migrate(uri, !!blk, blk, !!inc, inc,
> -                false, false, true, resume, &err);
> +    QAPI_LIST_PREPEND(caps, channel);
> +    qmp_migrate(uri, false, caps, !!blk, blk, !!inc, inc,
> +                 false, false, true, resume, &err);
> +    qapi_free_MigrationChannelList(caps);

Same comments here.

>      if (hmp_handle_error(mon, err)) {
>          return;
>      }
> diff --git a/migration/migration.c b/migration/migration.c
> index 52e2ec3502..65272ef739 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -465,10 +465,22 @@ static bool migrate_uri_parse(const char *uri,
>      return true;
>  }
>  
> -static void qemu_start_incoming_migration(const char *uri, Error **errp)
> +static void qemu_start_incoming_migration(const char *uri, bool has_channels,
> +                                          MigrationChannelList *channels,
> +                                          Error **errp)
>  {
>      g_autoptr(MigrationAddress) channel = g_new0(MigrationAddress, 1);
>  
> +    /*
> +     * Having preliminary checks for uri and channel
> +     */
> +    if (uri && has_channels) {
> +        error_setg(errp, "'uri' and 'channels' arguments are mutually "
> +                   "exclusive; exactly one of the two should be present in "
> +                   "'migrate-incoming' qmp command ");
> +        return;
> +    }
> +
>      /* URI is not suitable for migration? */
>      if (!migration_channels_and_uri_compatible(uri, errp)) {
>          return;
> @@ -1496,7 +1508,8 @@ void migrate_del_blocker(Error *reason)
>      migration_blockers = g_slist_remove(migration_blockers, reason);
>  }
>  
> -void qmp_migrate_incoming(const char *uri, Error **errp)
> +void qmp_migrate_incoming(const char *uri, bool has_channels,
> +                          MigrationChannelList *channels, Error **errp)
>  {
>      Error *local_err = NULL;
>      static bool once = true;
> @@ -1514,7 +1527,7 @@ void qmp_migrate_incoming(const char *uri, Error **errp)
>          return;
>      }
>  
> -    qemu_start_incoming_migration(uri, &local_err);
> +    qemu_start_incoming_migration(uri, has_channels, channels, &local_err);
>  
>      if (local_err) {
>          yank_unregister_instance(MIGRATION_YANK_INSTANCE);
> @@ -1550,7 +1563,7 @@ void qmp_migrate_recover(const char *uri, Error **errp)
>       * only re-setup the migration stream and poke existing migration
>       * to continue using that newly established channel.
>       */
> -    qemu_start_incoming_migration(uri, errp);
> +    qemu_start_incoming_migration(uri, false, NULL, errp);
>  }
>  
>  void qmp_migrate_pause(Error **errp)
> @@ -1684,7 +1697,8 @@ static bool migrate_prepare(MigrationState *s, bool blk, bool blk_inc,
>      return true;
>  }
>  
> -void qmp_migrate(const char *uri, bool has_blk, bool blk,
> +void qmp_migrate(const char *uri, bool has_channels,
> +                 MigrationChannelList *channels, bool has_blk, bool blk,
>                   bool has_inc, bool inc, bool has_detach, bool detach,
>                   bool has_resume, bool resume, Error **errp)
>  {
> @@ -1693,6 +1707,16 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
>      MigrationState *s = migrate_get_current();
>      g_autoptr(MigrationAddress) channel = g_new0(MigrationAddress, 1);
>  
> +    /*
> +     * Having preliminary checks for uri and channel
> +     */
> +    if (uri && has_channels) {
> +        error_setg(errp, "'uri' and 'channels' arguments are mutually "
> +                   "exclusive; exactly one of the two should be present in "
> +                   "'migrate' qmp command ");
> +        return;
> +    }
> +
>      /* URI is not suitable for migration? */
>      if (!migration_channels_and_uri_compatible(uri, errp)) {
>          return;
> diff --git a/qapi/migration.json b/qapi/migration.json
> index b583642c2d..34ac4e0a82 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -1458,6 +1458,34 @@
>      'exec': 'MigrationExecCommand',
>      'rdma': 'InetSocketAddress' } }
>  
> +##
> +# @MigrationChannelType:
> +#
> +# The migration channel-type request options.
> +#
> +# @main: Main outbound migration channel.
> +#
> +# Since 8.1
> +##
> +{ 'enum': 'MigrationChannelType',
> +  'data': [ 'main' ] }
> +
> +##
> +# @MigrationChannel:
> +#
> +# Migration stream channel parameters.
> +#
> +# @channel-type: Channel type for transfering packet information.
> +#
> +# @addr: Migration endpoint configuration on destination interface.
> +#
> +# Since 8.1
> +##
> +{ 'struct': 'MigrationChannel',
> +  'data': {
> +      'channel-type': 'MigrationChannelType',
> +      'addr': 'MigrationAddress' } }
> +
>  ##
>  # @migrate:
>  #
> @@ -1465,6 +1493,9 @@
>  #
>  # @uri: the Uniform Resource Identifier of the destination VM
>  #
> +# @channels: list of migration stream channels with each stream in the
> +#     list connected to a destination interface endpoint.
> +#
>  # @blk: do block migration (full disk copy)
>  #
>  # @inc: incremental disk copy migration
> @@ -1489,14 +1520,50 @@
>  # 3. The user Monitor's "detach" argument is invalid in QMP and should
>  #    not be used
>  #
> +# 4. The uri argument should have the Uniform Resource Identifier of
> +#    default destination VM. This connection will be bound to default
> +#    network.
> +#
> +# 5. For now, number of migration streams is restricted to one, i.e
> +#    number of items in 'channels' list is just 1.
> +#
> +# 6. The 'uri' and 'channels' arguments are mutually exclusive;
> +#    exactly one of the two should be present.
> +#
>  # Example:
>  #
>  # -> { "execute": "migrate", "arguments": { "uri": "tcp:0:4446" } }
>  # <- { "return": {} }
> +# -> { "execute": "migrate",
> +#      "arguments": {
> +#          "channels": [ { "channel-type": "main",
> +#                          "addr": { "transport": "socket",
> +#                                    "type": "inet",
> +#                                    "host": "10.12.34.9",
> +#                                    "port": "1050" } } ] } }
> +# <- { "return": {} }
> +#
> +# -> { "execute": "migrate",
> +#      "arguments": {
> +#          "channels": [ { "channel-type": "main",
> +#                          "addr": { "transport": "exec",
> +#                                    "args": [ "/bin/nc", "-p", "6000",
> +#                                              "/some/sock" ] } } ] } }
> +# <- { "return": {} }
> +#
> +# -> { "execute": "migrate",
> +#      "arguments": {
> +#          "channels": [ { "channel-type": "main",
> +#                          "addr": { "transport": "rdma",
> +#                                    "host": "10.12.34.9",
> +#                                    "port": "1050" } } ] } }
> +# <- { "return": {} }
> +#
>  ##
>  { 'command': 'migrate',
> -  'data': {'uri': 'str', '*blk': 'bool', '*inc': 'bool',
> -           '*detach': 'bool', '*resume': 'bool' } }
> +  'data': {'*uri': 'str', '*channels': [ 'MigrationChannel' ],
> +           '*blk': 'bool', '*inc': 'bool', '*detach': 'bool',
> +           '*resume': 'bool' } }
>  
>  ##
>  # @migrate-incoming:
> @@ -1507,6 +1574,9 @@
>  # @uri: The Uniform Resource Identifier identifying the source or
>  #     address to listen on
>  #
> +# @channels: list of migration stream channels with each stream in the
> +#     list connected to a destination interface endpoint.
> +#
>  # Returns: nothing on success
>  #
>  # Since: 2.3
> @@ -1522,13 +1592,46 @@
>  #
>  # 3. The uri format is the same as for -incoming
>  #
> +# 5. For now, number of migration streams is restricted to one, i.e
> +#    number of items in 'channels' list is just 1.
> +#
> +# 4. The 'uri' and 'channels' arguments are mutually exclusive;
> +#    exactly one of the two should be present.
> +#
>  # Example:
>  #
>  # -> { "execute": "migrate-incoming",
>  #      "arguments": { "uri": "tcp::4446" } }
>  # <- { "return": {} }
> +#
> +# -> { "execute": "migrate",
> +#      "arguments": {
> +#          "channels": [ { "channel-type": "main",
> +#                          "addr": { "transport": "socket",
> +#                                    "type": "inet",
> +#                                    "host": "10.12.34.9",
> +#                                    "port": "1050" } } ] } }
> +# <- { "return": {} }
> +#
> +# -> { "execute": "migrate",
> +#      "arguments": {
> +#          "channels": [ { "channel-type": "main",
> +#                          "addr": { "transport": "exec",
> +#                                    "args": [ "/bin/nc", "-p", "6000",
> +#                                              "/some/sock" ] } } ] } }
> +# <- { "return": {} }
> +#
> +# -> { "execute": "migrate",
> +#      "arguments": {
> +#          "channels": [ { "channel-type": "main",
> +#                          "addr": { "transport": "rdma",
> +#                                    "host": "10.12.34.9",
> +#                                    "port": "1050" } } ] } }
> +# <- { "return": {} }
>  ##
> -{ 'command': 'migrate-incoming', 'data': {'uri': 'str' } }
> +{ 'command': 'migrate-incoming',
> +             'data': {'*uri': 'str',
> +                      '*channels': [ 'MigrationChannel' ] } }
>  
>  ##
>  # @xen-save-devices-state:
> diff --git a/softmmu/vl.c b/softmmu/vl.c
> index b0b96f67fa..d811f3f878 100644
> --- a/softmmu/vl.c
> +++ b/softmmu/vl.c
> @@ -2651,7 +2651,7 @@ void qmp_x_exit_preconfig(Error **errp)
>      if (incoming) {
>          Error *local_err = NULL;
>          if (strcmp(incoming, "defer") != 0) {
> -            qmp_migrate_incoming(incoming, &local_err);
> +            qmp_migrate_incoming(incoming, false, NULL, &local_err);
>              if (local_err) {
>                  error_reportf_err(local_err, "-incoming %s: ", incoming);
>                  exit(1);
> -- 
> 2.22.3
> 

With regards,
Daniel
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