QMP/qmp-spec.txt - qemu - Git at Google

            QEMU Monitor Protocol Specification - Version 0.1

 1. Introduction
 ===============

 This document specifies the QEMU Monitor Protocol (QMP), a JSON-based protocol
 which is available for applications to control QEMU at the machine-level.

 To enable QMP support, QEMU has to be run in "control mode". This is done by
 starting QEMU with the appropriate command-line options. Please, refer to the
 QEMU manual page for more information.

 2. Protocol Specification
 =========================

 This section details the protocol format. For the purpose of this document
 "Client" is any application which is communicating with QEMU in control mode,
 and "Server" is QEMU itself.

 JSON data structures, when mentioned in this document, are always in the
 following format:

     json-DATA-STRUCTURE-NAME

 Where DATA-STRUCTURE-NAME is any valid JSON data structure, as defined by
 the JSON standard:

 http://www.ietf.org/rfc/rfc4627.txt

 For convenience, json-object members and json-array elements mentioned in
 this document will be in a certain order. However, in real protocol usage
 they can be in ANY order, thus no particular order should be assumed.

 2.1 General Definitions
 -----------------------

 2.1.1 All interactions transmitted by the Server are json-objects, always
       terminating with CRLF

 2.1.2 All json-objects members are mandatory when not specified otherwise

 2.2 Server Greeting
 -------------------

 Right when connected the Server will issue a greeting message, which signals
 that the connection has been successfully established and that the Server is
 ready for capabilities negotiation (for more information refer to section
 '4. Capabilities Negotiation').

 The format is:

 { "QMP": { "version": json-object, "capabilities": json-array } }

  Where,

 - The "version" member contains the Server's version information (the format
   is the same of the 'query-version' command)
 - The "capabilities" member specify the availability of features beyond the
   baseline specification

 2.3 Issuing Commands
 --------------------

 The format for command execution is:

 { "execute": json-string, "arguments": json-object, "id": json-value }

  Where,

 - The "execute" member identifies the command to be executed by the Server
 - The "arguments" member is used to pass any arguments required for the
   execution of the command, it is optional when no arguments are required
 - The "id" member is a transaction identification associated with the
   command execution, it is optional and will be part of the response if
   provided

 2.4 Commands Responses
 ----------------------

 There are two possible responses which the Server will issue as the result
 of a command execution: success or error.

 2.4.1 success
 -------------

 The success response is issued when the command execution has finished
 without errors.

 The format is:

 { "return": json-object, "id": json-value }

  Where,

 - The "return" member contains the command returned data, which is defined
   in a per-command basis or an empty json-object if the command does not
   return data
 - The "id" member contains the transaction identification associated
   with the command execution (if issued by the Client)

 2.4.2 error
 -----------

 The error response is issued when the command execution could not be
 completed because of an error condition.

 The format is:

 { "error": { "class": json-string, "data": json-object, "desc": json-string },
   "id": json-value }

  Where,

 - The "class" member contains the error class name (eg. "ServiceUnavailable")
 - The "data" member contains specific error data and is defined in a
   per-command basis, it will be an empty json-object if the error has no data
 - The "desc" member is a human-readable error message. Clients should
   not attempt to parse this message.
 - The "id" member contains the transaction identification associated with
   the command execution (if issued by the Client)

 NOTE: Some errors can occur before the Server is able to read the "id" member,
 in these cases the "id" member will not be part of the error response, even
 if provided by the client.

 2.5 Asynchronous events
 -----------------------

 As a result of state changes, the Server may send messages unilaterally
 to the Client at any time. They are called 'asynchronous events'.

 The format is:

 { "event": json-string, "data": json-object,
   "timestamp": { "seconds": json-number, "microseconds": json-number } }

  Where,

 - The "event" member contains the event's name
 - The "data" member contains event specific data, which is defined in a
   per-event basis, it is optional
 - The "timestamp" member contains the exact time of when the event occurred
   in the Server. It is a fixed json-object with time in seconds and
   microseconds

 For a listing of supported asynchronous events, please, refer to the
 qmp-events.txt file.

 3. QMP Examples
 ===============

 This section provides some examples of real QMP usage, in all of them
 'C' stands for 'Client' and 'S' stands for 'Server'.

 3.1 Server greeting
 -------------------

 S: {"QMP": {"version": {"qemu": "0.12.50", "package": ""}, "capabilities": []}}

 3.2 Simple 'stop' execution
 ---------------------------

 C: { "execute": "stop" }
 S: {"return": {}}

 3.3 KVM information
 -------------------

 C: { "execute": "query-kvm", "id": "example" }
 S: {"return": {"enabled": true, "present": true}, "id": "example"}

 3.4 Parsing error
 ------------------

 C: { "execute": }
 S: {"error": {"class": "JSONParsing", "desc": "Invalid JSON syntax", "data":
 {}}}

 3.5 Powerdown event
 -------------------

 S: {"timestamp": {"seconds": 1258551470, "microseconds": 802384}, "event":
 "POWERDOWN"}

 4. Capabilities Negotiation
 ----------------------------

 When a Client successfully establishes a connection, the Server is in
 Capabilities Negotiation mode.

 In this mode only the 'qmp_capabilities' command is allowed to run, all
 other commands will return the CommandNotFound error. Asynchronous messages
 are not delivered either.

 Clients should use the 'qmp_capabilities' command to enable capabilities
 advertised in the Server's greeting (section '2.2 Server Greeting') they
 support.

 When the 'qmp_capabilities' command is issued, and if it does not return an
 error, the Server enters in Command mode where capabilities changes take
 effect, all commands (except 'qmp_capabilities') are allowed and asynchronous
 messages are delivered.

 5 Compatibility Considerations
 ------------------------------

 All protocol changes or new features which modify the protocol format in an
 incompatible way are disabled by default and will be advertised by the
 capabilities array (section '2.2 Server Greeting'). Thus, Clients can check
 that array and enable the capabilities they support.

 Additionally, Clients must not assume any particular:

 - Size of json-objects or length of json-arrays
 - Order of json-object members or json-array elements
 - Amount of errors generated by a command, that is, new errors can be added
   to any existing command in newer versions of the Server
	QEMU Monitor Protocol Specification - Version 0.1

	1. Introduction
	===============

	This document specifies the QEMU Monitor Protocol (QMP), a JSON-based protocol
	which is available for applications to control QEMU at the machine-level.

	To enable QMP support, QEMU has to be run in "control mode". This is done by
	starting QEMU with the appropriate command-line options. Please, refer to the
	QEMU manual page for more information.

	2. Protocol Specification
	=========================

	This section details the protocol format. For the purpose of this document
	"Client" is any application which is communicating with QEMU in control mode,
	and "Server" is QEMU itself.

	JSON data structures, when mentioned in this document, are always in the
	following format:

	json-DATA-STRUCTURE-NAME

	Where DATA-STRUCTURE-NAME is any valid JSON data structure, as defined by
	the JSON standard:

	http://www.ietf.org/rfc/rfc4627.txt

	For convenience, json-object members and json-array elements mentioned in
	this document will be in a certain order. However, in real protocol usage
	they can be in ANY order, thus no particular order should be assumed.

	2.1 General Definitions
	-----------------------

	2.1.1 All interactions transmitted by the Server are json-objects, always
	terminating with CRLF

	2.1.2 All json-objects members are mandatory when not specified otherwise

	2.2 Server Greeting
	-------------------

	Right when connected the Server will issue a greeting message, which signals
	that the connection has been successfully established and that the Server is
	ready for capabilities negotiation (for more information refer to section
	'4. Capabilities Negotiation').

	The format is:

	{ "QMP": { "version": json-object, "capabilities": json-array } }

	Where,

	- The "version" member contains the Server's version information (the format
	is the same of the 'query-version' command)
	- The "capabilities" member specify the availability of features beyond the
	baseline specification

	2.3 Issuing Commands
	--------------------

	The format for command execution is:

	{ "execute": json-string, "arguments": json-object, "id": json-value }

	Where,

	- The "execute" member identifies the command to be executed by the Server
	- The "arguments" member is used to pass any arguments required for the
	execution of the command, it is optional when no arguments are required
	- The "id" member is a transaction identification associated with the
	command execution, it is optional and will be part of the response if
	provided

	2.4 Commands Responses
	----------------------

	There are two possible responses which the Server will issue as the result
	of a command execution: success or error.

	2.4.1 success
	-------------

	The success response is issued when the command execution has finished
	without errors.

	The format is:

	{ "return": json-object, "id": json-value }

	Where,

	- The "return" member contains the command returned data, which is defined
	in a per-command basis or an empty json-object if the command does not
	return data
	- The "id" member contains the transaction identification associated
	with the command execution (if issued by the Client)

	2.4.2 error
	-----------

	The error response is issued when the command execution could not be
	completed because of an error condition.

	The format is:

	{ "error": { "class": json-string, "data": json-object, "desc": json-string },
	"id": json-value }

	Where,

	- The "class" member contains the error class name (eg. "ServiceUnavailable")
	- The "data" member contains specific error data and is defined in a
	per-command basis, it will be an empty json-object if the error has no data
	- The "desc" member is a human-readable error message. Clients should
	not attempt to parse this message.
	- The "id" member contains the transaction identification associated with
	the command execution (if issued by the Client)

	NOTE: Some errors can occur before the Server is able to read the "id" member,
	in these cases the "id" member will not be part of the error response, even
	if provided by the client.

	2.5 Asynchronous events
	-----------------------

	As a result of state changes, the Server may send messages unilaterally
	to the Client at any time. They are called 'asynchronous events'.

	The format is:

	{ "event": json-string, "data": json-object,
	"timestamp": { "seconds": json-number, "microseconds": json-number } }

	Where,

	- The "event" member contains the event's name
	- The "data" member contains event specific data, which is defined in a
	per-event basis, it is optional
	- The "timestamp" member contains the exact time of when the event occurred
	in the Server. It is a fixed json-object with time in seconds and
	microseconds

	For a listing of supported asynchronous events, please, refer to the
	qmp-events.txt file.

	3. QMP Examples
	===============

	This section provides some examples of real QMP usage, in all of them
	'C' stands for 'Client' and 'S' stands for 'Server'.

	3.1 Server greeting
	-------------------

	S: {"QMP": {"version": {"qemu": "0.12.50", "package": ""}, "capabilities": []}}

	3.2 Simple 'stop' execution
	---------------------------

	C: { "execute": "stop" }
	S: {"return": {}}

	3.3 KVM information
	-------------------

	C: { "execute": "query-kvm", "id": "example" }
	S: {"return": {"enabled": true, "present": true}, "id": "example"}

	3.4 Parsing error
	------------------

	C: { "execute": }
	S: {"error": {"class": "JSONParsing", "desc": "Invalid JSON syntax", "data":
	{}}}

	3.5 Powerdown event
	-------------------

	S: {"timestamp": {"seconds": 1258551470, "microseconds": 802384}, "event":
	"POWERDOWN"}

	4. Capabilities Negotiation
	----------------------------

	When a Client successfully establishes a connection, the Server is in
	Capabilities Negotiation mode.

	In this mode only the 'qmp_capabilities' command is allowed to run, all
	other commands will return the CommandNotFound error. Asynchronous messages
	are not delivered either.

	Clients should use the 'qmp_capabilities' command to enable capabilities
	advertised in the Server's greeting (section '2.2 Server Greeting') they
	support.

	When the 'qmp_capabilities' command is issued, and if it does not return an
	error, the Server enters in Command mode where capabilities changes take
	effect, all commands (except 'qmp_capabilities') are allowed and asynchronous
	messages are delivered.

	5 Compatibility Considerations
	------------------------------

	All protocol changes or new features which modify the protocol format in an
	incompatible way are disabled by default and will be advertised by the
	capabilities array (section '2.2 Server Greeting'). Thus, Clients can check
	that array and enable the capabilities they support.

	Additionally, Clients must not assume any particular:

	- Size of json-objects or length of json-arrays
	- Order of json-object members or json-array elements
	- Amount of errors generated by a command, that is, new errors can be added
	to any existing command in newer versions of the Server