Re: [Qemu-devel] [v5 12/12] migration: Add commands to set and query parameter

[Li, Liang Z]

> >> The command takes a list of key-value pairs.  Looks like this
> >> (example stolen from your patch to qmp-commands.hx):
> >>
> >>     { "execute": "migrate-set-parameters",
> >>       "arguments": { "parameters":
> >>                      [ { "parameter": "compress-level", "value": 1 }
> >> ] } }
> >>
> >> Awkward.  I'd very much prefer
> >>
> >>     { "execute": "migrate-set-parameters",
> >>       "arguments": { "compress-level", 1 } }
> >>
> >> I.e. the command simply takes the parameters as optional arguments.
> >> Simpler, and a natural use of the schema language.
> >
> > Yes, it seems complicated.  Eric suggested to use this type of
> > interface, because it can support different type of parameters if some
> > new parameters will be added.
> 
> I don't understand.
> 
> Schema for the three parameters we have now:
> 
> { 'command': 'migrate-set-parameters',
>   'data': { '*compression-level': 'int',
>             '*compression-threads': 'int,
>             '*decompression-threads': 'int' } }
> 
> Let's add a parameter with some other type:
> 
> { 'command': 'migrate-set-parameters',
>   'data': { '*compression-level': 'int',
>             '*compression-threads': 'int,
>             '*compression-algorithm': 'CompressionAlgorithm',
>             '*decompression-threads': 'int', } }
> 
> CompressionAlgorithm could be an enum.
> 
> Why wouldn't that work?

To be honest, I know very little about QMP and JSON. What should I do to make 
the 
schema as you described?

 
> >> > +##
> >> > +# @query-migrate-parameters
> >> > +#
> >> > +# Returns information about the current migration parameters
> >> > +status # # Returns: @MigrationParametersStatus # # Since: 2.3 ##
> { 'command':
> >> > +'query-migrate-parameters',
> >> > +  'returns': ['MigrationParameterStatus'] } ##
> >> >  ##
> >> >  # @MouseInfo:
> >> >  #
> >>
> >> Produces a list of key-value pairs.  Looks like this (stolen from the
> >> same
> >> place):
> >>
> >>     {
> >>        "return": [
> >>           {
> >>              "parameter": "compress-level",
> >>              "value": 1
> >>           },
> >>           {
> >>              "parameter": "compress-threads",
> >>              "value": 8
> >>           },
> >>           {
> >>              "parameter": "decompress-threads",
> >>              "value": 2
> >>           }
> >>        ]
> >>     }
> >>
> >> I'd very much prefer a simple object instead:
> >>
> >>     { "return": { "compress-level": 1,
> >>                   "compress-threads": 8,
> >>                   "decompress-threads": 2 } }
> >>
> >
> > The same reason.
> 
> { 'command': 'query-migrate-parameters',
>   'returns': 'MigrationParameters' }
> 
> { 'type': 'MigrationParameters',
>   'data': { 'compression-level': 'int',
>             'compression-threads': 'int,
>             'decompression-threads': 'int' } }
> 
> Add one as above:
> 
> { 'type': 'MigrationParameters',
>   'data': { 'compression-level': 'int',
>             'compression-threads': 'int,
>             'compression-algorithm': 'CompressionAlgorithm',
>             'decompression-threads': 'int', } }
> 
> Why wouldn't that work?

Could you be kind to point out what changes should I make?