Re: [Qemu-devel] [PATCH 01/11] QMP: Introduce specification file

[Anthony Liguori]

Avi Kivity wrote:
> Merging is a meaningless milestone since the protocol will not be 
> enabled.  Since we'll miss 0.11 in reality we have 7-8 months before 
> the protocol can be used in production.  IMO you're optimizing for the 
> short term, disregarding long-term maintenance, and disregarding ease 
> of implementation for users of the qemu monitor.

QMP is:

__skip__: [ \t]+

symbol: [A-Za-z_\-]+
decimalinteger: [1-9][0-9]+
hexinteger: 0x[0-9]+
float: [0-9]+\.[0-9]+
string: \"([^\"\\]|(\\[0-9][0-9][0-9]))*\" | symbol

number: float | decimalinteger | hexinteger
value: string | number

arg_list: value arg_list?
command: symbol arg_list? '\n'

response_status: ('+' | '-') number arg_list? '\n'
response_data: '=' arg_list '\n'
async_msg: '*' arg_list '\n'

response: async_msg | response_data* response_status

Client sends 'command's, server responses with 'response'.  Responses of 
response type '*' are server initiated messages.  Otherwise, a server 
always responses to a command with a response type of '+' or '-'.  A 
client sits in a 'response' parsing loop.  Each sent 'command' is queued 
in a FIFO and responses are associated with the commands based on the 
FIFO order.  'async_msg's do not have associated commands.  All strings 
are UTF-8.  Human readable messages depend on the locale used by QEMU.

N.B. there are some subtle changes to Luiz's original proposal to make 
QMP more well-formed.  In particular, more things have to be encoded as 
strings than previously.

This is a very well formed RPC now.  It can be trivially implemented in 
something like Python.  We can add higher level types.  For instance, we 
could:

-value: string | number
+value: (string | number | list | dictionary)
+comma_arg_list: value (',' comma_arg_list)?
+list: '[' comma_arg_list? ']'
+
+dict_list: string ':' value (',' dict_list)?
+dictionary: '{' dict_list? '}'

And then we basically have JSON.  The changes on top of Luiz's current 
patchset would be introducing an error code and adding more structure to 
monitor_printf() which I asked for anyway.

Regards,

Anthony Liguori