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diff --git a/QMP/qmp-spec.txt b/QMP/qmp-spec.txt new file mode 100644 index 0000000000..8429789a9c --- /dev/null +++ b/QMP/qmp-spec.txt @@ -0,0 +1,192 @@ + QEMU Monitor Protocol Draft 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-objects mentioned in this document will have its members +in a certain order. However, in real protocol usage json-objects members 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 +waiting for commands. + +The format is: + +{ "QMP": { "capabilities": json-array } } + + Where, + +- 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-value, "id": json-value } + + Where, + +- The "return" member contains the command returned data, which is defined + in a per-command basis or "OK" 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-value }, "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 "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-value, + "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 ocurred + 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": {"capabilities": []}} + +3.2 Simple 'stop' execution +--------------------------- + +C: { "execute": "stop" } +S: {"return": "OK"} + +3.3 KVM information +------------------- + +C: {"execute": "query-kvm", "id": "example"} +S: {"return": "enabled", "id": "example"} + +3.4 Parsing error +------------------ + +C: { "execute": } +S: {"error": {"class": "JSONParsing", "data": {}}} + +3.5 Powerdown event +------------------- + +S: {"timestamp": {"seconds": 1258551470, "microseconds": 802384}, "event": +"POWERDOWN"} + +4. Notes to Client implementors +------------------------------- + +4.1 It is recommended to always start the Server in pause mode, thus the + Client is able to perform any setup procedure without the risk of + race conditions and related problems + +4.2 It is recommended to always check the capabilities json-array, issued + with the greeting message, at connection time + +4.3 Json-objects or json-arrays mentioned in this document are not fixed + and no particular size or number of members/elements should be assumed. + New members/elements can be added at any time. + +4.4 No particular order of json-objects members should be assumed, they + can change at any time |