Re: [PATCH 1/5] migration: Updated QAPI format for 'migrate' qemu monitor command

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Het Gala (het.gala@nutanix.com) wrote:
> From: Author Het Gala <het.gala@nutanix.com>
> 
> Existing 'migrate' QAPI design enforces transport mechanism, ip address
> of destination interface and corresponding port number in the form
> of a unified string 'uri' parameter. This scheme does seem to have an issue
> in it, i.e. double-level encoding of URIs.
> 
> The current patch maps existing QAPI design into a well-defined data
> structure - 'MigrateChannel' only from the design perspective. Please note that
> the existing 'uri' parameter is kept untouched for backward compatibility.
> 
> Suggested-by: Daniel P. Berrange <berrange@redhat.com>
> Suggested-by: Manish Mishra <manish.mishra@nutanix.com>
> Suggested-by: Aravind Retnakaran <aravind.retnakaran@nutanix.com>
> Signed-off-by: Het Gala <het.gala@nutanix.com>
> ---
>  qapi/migration.json | 121 +++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 119 insertions(+), 2 deletions(-)
> 
> diff --git a/qapi/migration.json b/qapi/migration.json
> index 88ecf86ac8..753e187ce2 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -1449,12 +1449,108 @@
>  ##
>  { 'command': 'migrate-continue', 'data': {'state': 'MigrationStatus'} }
>  
> +##
> +# @MigrateTransport:
> +#
> +# The supported communication transport mechanisms for migration
> +#
> +# @socket: Supported communication type between two devices for migration.
> +#          Socket is able to cover all of 'tcp', 'unix', 'vsock' and
> +#          'fd' already
> +#
> +# @exec: Supported communication type to redirect migration stream into file.
> +#
> +# @rdma: Supported communication type to redirect rdma type migration stream.
> +#
> +# Since 8.0
> +##
> +{ 'enum': 'MigrateTransport',
> +  'data': ['socket', 'exec', 'rdma'] }
> +
> +##
> +# @MigrateSocketAddr:
> +#
> +# To support different type of socket.
> +#
> +# @socket-type: Different type of socket connections.
> +#
> +# Since 8.0
> +##
> +{ 'struct': 'MigrateSocketAddr',
> +  'data': {'socket-type': 'SocketAddress' } }
> +
> +##
> +# @MigrateExecAddr:
> + #
> + # Since 8.0
> + ##
> +{ 'struct': 'MigrateExecAddr',
> +   'data' : {'exec-str': 'str' } }
> +
> +##
> +# @MigrateRdmaAddr:
> +#
> +# Since 8.0
> +##
> +{ 'struct': 'MigrateRdmaAddr',
> +   'data' : {'rdma-str': 'str' } }
> +
> +##
> +# @MigrateAddress:
> +#
> +# The options available for communication transport mechanisms for migration
> +#
> +# Since 8.0
> +##
> +{ 'union' : 'MigrateAddress',
> +  'base' : { 'transport' : 'MigrateTransport'},
> +  'discriminator' : 'transport',
> +  'data' : {
> +    'socket' : 'MigrateSocketAddr',
> +    'exec' : 'MigrateExecAddr',
> +    'rdma': 'MigrateRdmaAddr' } }
> +
> +##
> +# @MigrateChannelType:
> +#
> +# The supported options for migration channel type requests
> +#
> +# @main: Support request for main outbound migration control channel
> +#
> +# Since 8.0
> +##
> +{ 'enum': 'MigrateChannelType',
> +  'data': [ 'main'] }
> +
> +##
> +# @MigrateChannel:
> +#
> +# Information regarding migration Channel-type for transferring packets,
> +# source and corresponding destination interface for socket connection
> +# and number of multifd channels over the interface.
> +#
> +# @channeltype: Name of Channel type for transfering packet information
> +#
> +# @addr: SocketAddress of destination interface
> +#
> +# Since 8.0
> +##
> +{ 'struct': 'MigrateChannel',
> +  'data' : {
> +	'channeltype' : 'MigrateChannelType',
> +	'addr' : 'MigrateAddress' } }
> +

The presence of the channeltype field suggests you're going to try to
support multiple addresses; that's OK, but can you show an example of
how that might look in the migrate command below?

Dave

>  ##
>  # @migrate:
>  #
>  # Migrates the current running guest to another Virtual Machine.
>  #
>  # @uri: the Uniform Resource Identifier of the destination VM
> +#       for migration thread
> +#
> +# @channel: Struct containing migration channel type, along with all
> +#           the details of destination interface required for initiating
> +#           a migration stream.
>  #
>  # @blk: do block migration (full disk copy)
>  #
> @@ -1479,15 +1575,36 @@
>  # 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. Both 'uri' and 'channel' arguments, are mututally exclusive but, atleast
> +#    one of the two arguments should be present.
> +#
>  # Example:
>  #
>  # -> { "execute": "migrate", "arguments": { "uri": "tcp:0:4446" } }
>  # <- { "return": {} }
>  #
> +# -> { "execute": "migrate",
> +#      "arguments": {
> +#          "channel": { "channeltype": "main",
> +#                        "addr": { "transport": "socket",
> +#                                  "socket-type": { "type': "inet',
> +#                                                   "host": "10.12.34.9",
> +#                                                   "port": "1050" } } } } }
> +# <- { "return": {} }
> +#
> +# -> { "execute": "migrate",
> +#      "arguments": { "channel": { "channeltype": "main",
> +#                                  "addr": { "transport": "exec",
> +#                                            "exec-str": "/tmp/exec" } } } }
> +# <- { "return": {} }
> +#
>  ##
>  { 'command': 'migrate',
> -  'data': {'uri': 'str', '*blk': 'bool', '*inc': 'bool',
> -           '*detach': 'bool', '*resume': 'bool' } }
> +  'data': {'*uri': 'str', '*channel': 'MigrateChannel', '*blk': 'bool',
> +           '*inc': 'bool', '*detach': 'bool', '*resume': 'bool' } }
>  
>  ##
>  # @migrate-incoming:
> -- 
> 2.22.3
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK