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

[Het Gala]

On 17/01/23 4:17 pm, Dr. David Alan Gilbert wrote:
> * 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

Yes Dave. Other options will be "data" (for multifd) and "post-copy" 
(for post-copy migration).

I am not very sure how will we represent "post-copy" part, but I will 
give you an example of how "main" and "data" Channels will be 
represented by an example below:

-> { "execute": "migrate",
       "arguments": {
            "channels": [ { 'channeltype': 'main',
                                  'addr': {'transport': 'socket',
                                             'socket-type': { 'type': 
'inet',
'host': '10.12.34.9', 'port': '1050'} }
                                { 'channeltype': 'data',
                                  'addr': {'transport': 'socket',
                                             'socket-type': { 'type': 
'inet',
'host': '10.12.34.92', 'port': '1234'},
                                  'multifd-count': 5 },
                                { 'channeltype': 'data',
                                  'addr': { 'transport': 'socket',
                                              'socket-type': {'type': 
'inet',
'host': '0.0.0.4', 'port': '3000'},
                                  'multifd-count': 3 } ] } }
So, 'data' channels will be used for multi-fd conection while 'main' 
will be used for just normal migration connection.
This 'data' channel option has been planned with a whole different 
patchset series in future.
Let me know if you have any more doubts regarding this :)
> >   #
> >   # -> { "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:
Regards,
Het Gala