QMP: Update qmp-spec.txt
Simplify the text, fix some of the examples. Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
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Luiz Capitulino
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QEMU Monitor Protocol Specification - Version 0.1
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QEMU Machine Protocol Specification
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1. Introduction
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===============
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This document specifies the QEMU Monitor Protocol (QMP), a JSON-based protocol
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which is available for applications to control QEMU at the machine-level.
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To enable QMP support, QEMU has to be run in "control mode". This is done by
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starting QEMU with the appropriate command-line options. Please, refer to the
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QEMU manual page for more information.
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This document specifies the QEMU Machine Protocol (QMP), a JSON-based protocol
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which is available for applications to operate QEMU at the machine-level.
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2. Protocol Specification
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=========================
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This section details the protocol format. For the purpose of this document
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"Client" is any application which is communicating with QEMU in control mode,
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and "Server" is QEMU itself.
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"Client" is any application which is using QMP to communicate with QEMU and
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"Server" is QEMU itself.
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JSON data structures, when mentioned in this document, are always in the
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following format:
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@ -47,14 +43,14 @@ that the connection has been successfully established and that the Server is
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ready for capabilities negotiation (for more information refer to section
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'4. Capabilities Negotiation').
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The format is:
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The greeting message format is:
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{ "QMP": { "version": json-object, "capabilities": json-array } }
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Where,
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- The "version" member contains the Server's version information (the format
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is the same of the 'query-version' command)
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is the same of the query-version command)
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- The "capabilities" member specify the availability of features beyond the
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baseline specification
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@ -83,10 +79,7 @@ of a command execution: success or error.
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2.4.1 success
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-------------
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The success response is issued when the command execution has finished
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without errors.
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The format is:
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The format of a success response is:
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{ "return": json-object, "id": json-value }
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@ -96,15 +89,12 @@ The format is:
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in a per-command basis or an empty json-object if the command does not
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return data
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- The "id" member contains the transaction identification associated
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with the command execution (if issued by the Client)
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with the command execution if issued by the Client
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2.4.2 error
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-----------
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The error response is issued when the command execution could not be
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completed because of an error condition.
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The format is:
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The format of an error response is:
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{ "error": { "class": json-string, "desc": json-string }, "id": json-value }
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@ -114,7 +104,7 @@ The format is:
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- The "desc" member is a human-readable error message. Clients should
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not attempt to parse this message.
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- The "id" member contains the transaction identification associated with
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the command execution (if issued by the Client)
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the command execution if issued by the Client
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NOTE: Some errors can occur before the Server is able to read the "id" member,
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in these cases the "id" member will not be part of the error response, even
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@ -124,9 +114,9 @@ if provided by the client.
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-----------------------
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As a result of state changes, the Server may send messages unilaterally
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to the Client at any time. They are called 'asynchronous events'.
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to the Client at any time. They are called "asynchronous events".
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The format is:
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The format of asynchronous events is:
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{ "event": json-string, "data": json-object,
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"timestamp": { "seconds": json-number, "microseconds": json-number } }
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@ -147,36 +137,37 @@ qmp-events.txt file.
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===============
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This section provides some examples of real QMP usage, in all of them
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'C' stands for 'Client' and 'S' stands for 'Server'.
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"C" stands for "Client" and "S" stands for "Server".
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3.1 Server greeting
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-------------------
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S: {"QMP": {"version": {"qemu": "0.12.50", "package": ""}, "capabilities": []}}
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S: { "QMP": { "version": { "qemu": { "micro": 50, "minor": 6, "major": 1 },
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"package": ""}, "capabilities": []}}
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3.2 Simple 'stop' execution
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---------------------------
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C: { "execute": "stop" }
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S: {"return": {}}
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S: { "return": {} }
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3.3 KVM information
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-------------------
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C: { "execute": "query-kvm", "id": "example" }
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S: {"return": {"enabled": true, "present": true}, "id": "example"}
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S: { "return": { "enabled": true, "present": true }, "id": "example"}
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3.4 Parsing error
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------------------
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C: { "execute": }
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S: {"error": {"class": "GenericError", "desc": "Invalid JSON syntax" } }
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S: { "error": { "class": "GenericError", "desc": "Invalid JSON syntax" } }
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3.5 Powerdown event
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-------------------
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S: {"timestamp": {"seconds": 1258551470, "microseconds": 802384}, "event":
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"POWERDOWN"}
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S: { "timestamp": { "seconds": 1258551470, "microseconds": 802384 },
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"event": "POWERDOWN" }
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4. Capabilities Negotiation
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----------------------------
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@ -184,17 +175,17 @@ S: {"timestamp": {"seconds": 1258551470, "microseconds": 802384}, "event":
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When a Client successfully establishes a connection, the Server is in
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Capabilities Negotiation mode.
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In this mode only the 'qmp_capabilities' command is allowed to run, all
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other commands will return the CommandNotFound error. Asynchronous messages
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are not delivered either.
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In this mode only the qmp_capabilities command is allowed to run, all
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other commands will return the CommandNotFound error. Asynchronous
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messages are not delivered either.
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Clients should use the 'qmp_capabilities' command to enable capabilities
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Clients should use the qmp_capabilities command to enable capabilities
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advertised in the Server's greeting (section '2.2 Server Greeting') they
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support.
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When the 'qmp_capabilities' command is issued, and if it does not return an
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When the qmp_capabilities command is issued, and if it does not return an
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error, the Server enters in Command mode where capabilities changes take
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effect, all commands (except 'qmp_capabilities') are allowed and asynchronous
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effect, all commands (except qmp_capabilities) are allowed and asynchronous
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messages are delivered.
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5 Compatibility Considerations
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@ -245,7 +236,7 @@ arguments, errors, asynchronous events, and so forth.
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Any new names downstream wishes to add must begin with '__'. To
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ensure compatibility with other downstreams, it is strongly
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recommended that you prefix your downstram names with '__RFQDN_' where
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recommended that you prefix your downstream names with '__RFQDN_' where
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RFQDN is a valid, reverse fully qualified domain name which you
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control. For example, a qemu-kvm specific monitor command would be:
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