[Qemu-devel] [PATCH v7 00/23] QMP: out-of-band (OOB) execution support

[Qemu-devel] [PATCH v7 00/23] QMP: out-of-band (OOB) execution support

[Peter Xu]

This version should have addressed all comments in previous one, also
fixed another race condition after I addressed all the comments (a new
race condition introduced by addressing the comments...).  For some
more details of the race condition, please see the last entry of
change log, and please refer to patch 9 for the code change.

I removed RFC tag from this version.  Please review.  Thanks.

v7:
- add some r-bs, and remove some.
- remove the chardev fix since already queued by Paolo
- use local var in qemu_chr_fe_add_watch [Stefan]
- move doc patch to front, mention it in some patches [Eric]
- Quite a few of English fixes [Eric]
- fix unlock missing in handle_qmp_command [Stefan]
- squash some patches according to the review comments
- don't break gdbserver usage on HMP non-interactive mode by fixing up
  the suspend/resume logic [Fam, Stefan]
- move the qemu_chr_fe_set_handlers() call in monitor_init() into a
  bottom half to avoid race between the call itself and
  iothread. [Stefan]
- spent quite a lot of time debugging another assertion failure in
  io_watch_poll_finalize() after above change is made (ouch! I really
  hoped we always have the latest glib): when QEMU inits chardevs in
  chardev_init_func() it's possible that QEMU registers the chardev
  handlers there, even before CharBackend is connected to that chardev
  in monitor_init().  Then, when we reach monitor_init() we must make
  sure we unregister that old one first, or there can have one orphan
  GSource still in default gcontext (note that this can really happen
  when we start to use QEMUBH to setup chardev frontends, which is
  above change).

v6:
- add r-bs
- s/negociate/negotiate/ [Dave]
- let mon_global be anonymous struct [Stefan]
- in monitor_init(): call qemu_chr_fe_set_handlers() later than init
  parser, then it's safe [Stefan]
- drop patch "qjson: add "opaque" field to JSONMessageParser",
  re-write the following one to use container_of(). [Stefan]
- keep get_qmp_greeting() the old way, add cap list [Stefan, Fam]
- fix the iothread_stop() comment since that's not really related to
  the glib bug [Stefan]
- when do qmp greeting, don't expose oob capability if iothread not
  used [Stefan, Fam]
- squash "qmp: introduce some capability helpers" into patch "monitor:
  separate QMP parser and dispatcher" [Fam]
- tune comments for monitor_qmp_respond(). [Stefan]
- use atomic_mb_{read|set}() where proper instead of no-mb ones
  [Stefan]
- add patch to let monitor suspend/resume really support QMP.  Notify
  iothread when needed, in both suspend/resume. [Stefan]
- add comment for qmp_queue_lock on lock taking ordering. [Stefan]
- refactor monitor_qmp_bh_dispatcher() to not loop, instead queue
  itself after each request. [Stefan]
- rename "request" into "command" in the new qmp event [Stefan]
- in handle_qmp_command() protect the queue length fetch with
  qmp_queue_lock [Stefan]
- one more s/2.11/2.12/.  [Fam]
- when isolating response queue, not only flush the queue, but also
  flush the monitor out buffer [Stefan]
- document rewrite [Stefan]
- some other touch-ups that I forgot to mention and some tiny new
  patches... anyway, rbs will be gone if any of the patch is touched
  up.  Please have a look!

v5
- rename "monitor_iothread" to "mon_iothread" [Dave]
- add comment in monitor_cleanup(), note that when the hacks can be
  removed. [Dan]
- add a note section in qmp-spec.txt, mentioning about how to migrate
  existing QMP command to oob-capable command. [Dave]
- drop patch "qmp: let migrate-incoming allow out-of-band".  All
  migration related changes will all be put into postcopy-recovery
  series.

v4:
- drop first patch to fix IOWatchPool [Stefan, Dan]
- add s-o-b where missing, and newly got r-bs
- fix English error in commit msg [Fam]
- some tunes on request-dropped event:  [Stefan]
  - firstly let 'id' be any type, meanwhile make sure "id" is there as
    long as OOB is enabled for the monitor.
  - some comments fix
- add new command "x-oob-test" for testing oob commands [Stefan]
- simplify the test codes to use new x-oob-test
- flush response queue before cleanup monitors

This series was born from this one:

  https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04310.html

The idea comes from Markus Armbruster and the discussion we had in the
thread.  It's not a super ideal solution (I believe Markus had been
thinking hard to keep everything in order meanwhile trying to satisfy
the migration requirement), but AFAIU it's currently the best.

What is OOB?
============

It's the shortcut of Out-Of-Band execution, its name is given by
Markus.  It's a way to quickly execute a QMP request.  Say, originally
QMP is going throw these steps:

      JSON Parser --> QMP Dispatcher --> Respond
          /|\    (2)                (3)     |
       (1) |                               \|/ (4)
           +---------  main thread  --------+

The requests are executed by the so-called QMP-dispatcher after the
JSON is parsed.  If OOB is on, we run the command directly in the
parser and quickly returns.

This series changed the QMP handling logic by moving the command
parsing and responding phases into IOThreads, so to be more accurate,
after the series the above graph would change into this:

               queue/kick              queue/kick
     JSON Parser ======> QMP Dispatcher =====> Responder
         /|\ |     (3)       /|\  |      (4)      | /|\
      (1) |  | (2)            |   |               |  |
          |  |                |  \|/           (6)|  |(5)
          |  |            main thread             |  |
          |  |                                    |  |
          |  +--------> monitor IO thread <-------+  |
          +-----------/                   \----------+

New Interfaces
==============

QMP Introspection Changes
-------------------------

When do query-qmp-schema, we were getting something like:

  {"name": "migrate-incoming", "ret-type": "17",
   "meta-type": "command", "arg-type": "89"}

Now we will get a new key named "allow-oob":

  {"name": "migrate-incoming", "ret-type": "17", "allow-oob": true,
   "meta-type": "command", "arg-type": "89"}

Which shows whether a command supports OOB.

QMP Negociation Changes
-----------------------

We were running "qmp_capabilities" always without parameters like:

  {"execute": "qmp_capabilities"}

Now we can enable capabilities (we don't have any capability before
this series) like OOB using:

  {"execute": "qmp_capabilities", "arguments": {"enable": ["oob"]}}

Only after we explicitly enable OOB capability can we send requests in
OOB manner.  Otherwise we'll have exactly the same QMP session as
before, just like when OOB is not there.

When OOB is enabled, it's possible that OOB reply reaches faster than
previous command, so clients should be prepared.

Trigger OOB execution
---------------------

Let's take migrate-incoming as example.  The old command looks like:

  {"execute": "migrate-incoming", "arguments" : {"uri": "xxxxxx"}}

To execute a command with OOB execution, we need to specify it in the
QMP request in the extra "control" key:

  {"execute": "migrate-incoming", "arguments" : {"uri": "xxxxxx"},
   "control" { "run-oob": true } }

Then the command will be run in parser, and it can preempt other
commands.

Others
=================

The last patch of OOB test may need some attention.  I used
dump-guest-memory as a time-consuming command to test whether OOB is
working, and the only command I can test now is "migrate-incoming".  I
hope that is a "okay" solution for unit tests.  Any other suggestions
on that would be welcomed.

Please review.  Thanks.

Peter Xu (23):
  docs: update QMP documents for OOB commands
  qobject: introduce qstring_get_try_str()
  qobject: introduce qobject_get_try_str()
  qobject: let object_property_get_str() use new API
  monitor: move skip_flush into monitor_data_init
  monitor: move the cur_mon hack deeper for QMP
  monitor: unify global init
  monitor: let mon_list be tail queue
  monitor: allow using IO thread for parsing
  qmp: introduce QMPCapability
  monitor: introduce monitor_qmp_respond()
  monitor: let suspend_cnt be thread safe
  monitor: let suspend/resume work even with QMPs
  monitor: separate QMP parser and dispatcher
  qmp: add new event "command-dropped"
  monitor: send event when command queue full
  qapi: introduce new cmd option "allow-oob"
  qmp: support out-of-band (oob) execution
  qmp: isolate responses into io thread
  monitor: enable IO thread for (qmp & !mux) typed
  qmp: add command "x-oob-test"
  tests: qmp-test: verify command batching
  tests: qmp-test: add oob test

 docs/devel/qapi-code-gen.txt   |  68 +++-
 docs/interop/qmp-spec.txt      |  30 +-
 include/monitor/monitor.h      |   2 +-
 include/qapi/qmp/dispatch.h    |   3 +
 include/qapi/qmp/qstring.h     |   2 +
 monitor.c                      | 699 ++++++++++++++++++++++++++++++++++++-----
 qapi-schema.json               |  87 ++++-
 qapi/introspect.json           |   6 +-
 qapi/qmp-dispatch.c            |  32 +-
 qmp.c                          |  16 +
 qobject/qstring.c              |  21 ++
 qom/object.c                   |   9 +-
 scripts/qapi-commands.py       |  19 +-
 scripts/qapi-introspect.py     |  10 +-
 scripts/qapi.py                |  15 +-
 scripts/qapi2texi.py           |   2 +-
 tests/qapi-schema/test-qapi.py |   2 +-
 tests/qmp-test.c               |  97 +++++-
 trace-events                   |   3 +
 vl.c                           |   7 +-
 20 files changed, 1016 insertions(+), 114 deletions(-)

-- 
2.14.3

[Qemu-devel] [PATCH v7 01/23] docs: update QMP documents for OOB commands

[Peter Xu]

Update both the developer and spec for the new QMP OOB (Out-Of-Band)
command.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 docs/devel/qapi-code-gen.txt | 68 ++++++++++++++++++++++++++++++++++++++++----
 docs/interop/qmp-spec.txt    | 30 ++++++++++++++++---
 2 files changed, 89 insertions(+), 9 deletions(-)

diff --git a/docs/devel/qapi-code-gen.txt b/docs/devel/qapi-code-gen.txt
index 06ab699066..4d3db0ad39 100644
--- a/docs/devel/qapi-code-gen.txt
+++ b/docs/devel/qapi-code-gen.txt
@@ -554,9 +554,12 @@ following example objects:
 
 === Commands ===
 
+--- General Command Layout ---
+
 Usage: { 'command': STRING, '*data': COMPLEX-TYPE-NAME-OR-DICT,
          '*returns': TYPE-NAME, '*boxed': true,
-         '*gen': false, '*success-response': false }
+         '*gen': false, '*success-response': false,
+         '*allow-oob': false }
 
 Commands are defined by using a dictionary containing several members,
 where three members are most common.  The 'command' member is a
@@ -636,6 +639,59 @@ possible, the command expression should include the optional key
 'success-response' with boolean value false.  So far, only QGA makes
 use of this member.
 
+A command can be declared to support Out-Of-Band (OOB) execution.  By
+default, commands do not support OOB.  To declare a command to support
+it, we need an extra 'allow-oob' field.  For example:
+
+ { 'command': 'migrate_recover',
+   'data': { 'uri': 'str' }, 'allow-oob': true }
+
+To execute a command in Out-Of-Band way, we need to specify the
+"control" field in the request, with "run-oob" set to true. Example:
+
+ => { "execute": "command-support-oob",
+      "arguments": { ... },
+      "control": { "run-oob": true } }
+ <= { "return": { } }
+
+Without it, even the commands that support out-of-band execution will
+still be run In-Band.
+
+Please read the "Out-Of-Band Command Execution" section below for more
+information on how OOB execution works.
+
+--- About Out-Of-Band (OOB) Command Execution ---
+
+Out-Of-Band does not mean a special kind of command. Instead, it's a
+special way to execute the command.  One normal command can be
+declared to support Out-Of-Band execution when 'allow-oob' field is
+set to true when defining the command.  With that, it can be run in an
+Out-Of-Band way if 'run-oob' is specified in 'control' field of
+command request.
+
+When we say normal QMP command executions, it means basically the
+following:
+
+- They are executed in order,
+- They run only in main thread of QEMU,
+- They have the BQL taken during execution.
+
+For OOB command executions, they differ in the following:
+
+- They can be executed before an existing command,
+- They run in a monitor dedicated thread,
+- They do not take the BQL during execution.
+
+OOB command handlers must satisfy the following conditions:
+
+- It executes extremely fast,
+- It does not take any lock, or, it can take very small locks if all
+  critical regions also follow the rules for OOB command handler code,
+- It does not invoke system calls that may block,
+- It does not access guest RAM that may block when userfaultfd is
+  enabled for postcopy live migration.
+
+If in doubt, do not implement OOB execution support.
 
 === Events ===
 
@@ -739,10 +795,12 @@ references by name.
 QAPI schema definitions not reachable that way are omitted.
 
 The SchemaInfo for a command has meta-type "command", and variant
-members "arg-type" and "ret-type".  On the wire, the "arguments"
-member of a client's "execute" command must conform to the object type
-named by "arg-type".  The "return" member that the server passes in a
-success response conforms to the type named by "ret-type".
+members "arg-type", "ret-type" and "allow-oob".  On the wire, the
+"arguments" member of a client's "execute" command must conform to the
+object type named by "arg-type".  The "return" member that the server
+passes in a success response conforms to the type named by
+"ret-type".  When "allow-oob" is set, it means the command supports
+out-of-band execution.
 
 If the command takes no arguments, "arg-type" names an object type
 without members.  Likewise, if the command returns nothing, "ret-type"
diff --git a/docs/interop/qmp-spec.txt b/docs/interop/qmp-spec.txt
index f8b5356015..e20163c138 100644
--- a/docs/interop/qmp-spec.txt
+++ b/docs/interop/qmp-spec.txt
@@ -83,16 +83,27 @@ The greeting message format is:
 2.2.1 Capabilities
 ------------------
 
-As of the date this document was last revised, no server or client
-capability strings have been defined.
+Currently supported capabilities are:
 
+- "oob": it means the QMP server supports "Out-Of-Band" command
+  execution.  For more detail, please see "run-oob" parameter in
+  "Issuing Commands" section below.  Not all commands allow this "oob"
+  execution.  One can know whether one command supports "oob" by
+  "query-qmp-schema" command.
+
+QMP clients can get a list of supported QMP capabilities of the QMP
+server in the greeting message mentioned above.  By default, all the
+capabilities are off.  To enable a specific or multiple of QMP
+capabilities, QMP client needs to send "qmp_capabilities" command with
+extra parameter for the capabilities.
 
 2.3 Issuing Commands
 --------------------
 
 The format for command execution is:
 
-{ "execute": json-string, "arguments": json-object, "id": json-value }
+{ "execute": json-string, "arguments": json-object, "id": json-value,
+  "control": json-dict }
 
  Where,
 
@@ -102,10 +113,16 @@ The format for command execution is:
   required. Each command documents what contents will be considered
   valid when handling the json-argument
 - The "id" member is a transaction identification associated with the
-  command execution, it is optional and will be part of the response if
+  command execution.  It is required if OOB is enabled, and optional
+  if not.  The same "id" field will be part of the response if
   provided. The "id" member can be any json-value, although most
   clients merely use a json-number incremented for each successive
   command
+- The "control" member is optional, and currently only used for
+  "out-of-band" execution ("oob" as shortcut). The handling or
+  response of an "oob" command can overtake prior in-band commands.
+  To enable "oob" feature, just provide a control field with: {
+  "control": { "run-oob": true } }
 
 2.4 Commands Responses
 ----------------------
@@ -113,6 +130,11 @@ The format for command execution is:
 There are two possible responses which the Server will issue as the result
 of a command execution: success or error.
 
+As long as the commands were issued with a proper "id" field, then the
+same "id" field will be attached in the corresponding response message
+so that requests and responses can match.  Clients should drop all the
+responses that are with unknown "id" field.
+
 2.4.1 success
 -------------
 
-- 
2.14.3

[Qemu-devel] [PATCH v7 02/23] qobject: introduce qstring_get_try_str()

[Peter Xu]

The only difference from qstring_get_str() is that it allows the qstring
to be NULL.  If so, NULL is returned.

CC: Eric Blake <eblake@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/qapi/qmp/qstring.h |  1 +
 qobject/qstring.c          | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/include/qapi/qmp/qstring.h b/include/qapi/qmp/qstring.h
index 65c05a9be5..a145c8ca00 100644
--- a/include/qapi/qmp/qstring.h
+++ b/include/qapi/qmp/qstring.h
@@ -27,6 +27,7 @@ QString *qstring_from_str(const char *str);
 QString *qstring_from_substr(const char *str, int start, int end);
 size_t qstring_get_length(const QString *qstring);
 const char *qstring_get_str(const QString *qstring);
+const char *qstring_get_try_str(const QString *qstring);
 void qstring_append_int(QString *qstring, int64_t value);
 void qstring_append(QString *qstring, const char *str);
 void qstring_append_chr(QString *qstring, int c);
diff --git a/qobject/qstring.c b/qobject/qstring.c
index 74182a1c02..7638ab990d 100644
--- a/qobject/qstring.c
+++ b/qobject/qstring.c
@@ -128,6 +128,16 @@ const char *qstring_get_str(const QString *qstring)
     return qstring->string;
 }
 
+/**
+ * qstring_get_try_str(): Return a pointer to the stored string
+ *
+ * NOTE: will return NULL if qstring is not provided.
+ */
+const char *qstring_get_try_str(const QString *qstring)
+{
+    return qstring ? qstring_get_str(qstring) : NULL;
+}
+
 /**
  * qstring_is_equal(): Test whether the two QStrings are equal
  */
-- 
2.14.3

[Qemu-devel] [PATCH v7 03/23] qobject: introduce qobject_get_try_str()

[Peter Xu]

A quick way to fetch string from qobject when it's a QString.

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/qapi/qmp/qstring.h |  1 +
 qobject/qstring.c          | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/include/qapi/qmp/qstring.h b/include/qapi/qmp/qstring.h
index a145c8ca00..6517d8e377 100644
--- a/include/qapi/qmp/qstring.h
+++ b/include/qapi/qmp/qstring.h
@@ -28,6 +28,7 @@ QString *qstring_from_substr(const char *str, int start, int end);
 size_t qstring_get_length(const QString *qstring);
 const char *qstring_get_str(const QString *qstring);
 const char *qstring_get_try_str(const QString *qstring);
+const char *qobject_get_try_str(const QObject *qstring);
 void qstring_append_int(QString *qstring, int64_t value);
 void qstring_append(QString *qstring, const char *str);
 void qstring_append_chr(QString *qstring, int c);
diff --git a/qobject/qstring.c b/qobject/qstring.c
index 7638ab990d..e556b1afdf 100644
--- a/qobject/qstring.c
+++ b/qobject/qstring.c
@@ -138,6 +138,17 @@ const char *qstring_get_try_str(const QString *qstring)
     return qstring ? qstring_get_str(qstring) : NULL;
 }
 
+/**
+ * qobject_get_try_str(): Return a pointer to the corresponding string
+ *
+ * NOTE: the string will only be returned if the object is valid, and
+ * its type is QString, otherwise NULL is returned.
+ */
+const char *qobject_get_try_str(const QObject *qstring)
+{
+    return qstring_get_try_str(qobject_to_qstring(qstring));
+}
+
 /**
  * qstring_is_equal(): Test whether the two QStrings are equal
  */
-- 
2.14.3

[Qemu-devel] [PATCH v7 04/23] qobject: let object_property_get_str() use new API

[Peter Xu]

We can simplify object_property_get_str() using the new
qobject_get_try_str().

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 qom/object.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/qom/object.c b/qom/object.c
index c58c52d518..9cbeb51f0b 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1116,18 +1116,15 @@ char *object_property_get_str(Object *obj, const char *name,
                               Error **errp)
 {
     QObject *ret = object_property_get_qobject(obj, name, errp);
-    QString *qstring;
     char *retval;
 
     if (!ret) {
         return NULL;
     }
-    qstring = qobject_to_qstring(ret);
-    if (!qstring) {
+
+    retval = g_strdup(qobject_get_try_str(ret));
+    if (!retval) {
         error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name, "string");
-        retval = NULL;
-    } else {
-        retval = g_strdup(qstring_get_str(qstring));
     }
 
     qobject_decref(ret);
-- 
2.14.3

[Qemu-devel] [PATCH v7 05/23] monitor: move skip_flush into monitor_data_init

[Peter Xu]

It's part of the data init.  Collect it.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/monitor.c b/monitor.c
index b9da5e20d1..3a28a6d935 100644
--- a/monitor.c
+++ b/monitor.c
@@ -567,13 +567,14 @@ static void monitor_qapi_event_init(void)
 
 static void handle_hmp_command(Monitor *mon, const char *cmdline);
 
-static void monitor_data_init(Monitor *mon)
+static void monitor_data_init(Monitor *mon, bool skip_flush)
 {
     memset(mon, 0, sizeof(Monitor));
     qemu_mutex_init(&mon->out_lock);
     mon->outbuf = qstring_new();
     /* Use *mon_cmds by default. */
     mon->cmd_table = mon_cmds;
+    mon->skip_flush = skip_flush;
 }
 
 static void monitor_data_destroy(Monitor *mon)
@@ -594,8 +595,7 @@ char *qmp_human_monitor_command(const char *command_line, bool has_cpu_index,
     char *output = NULL;
     Monitor *old_mon, hmp;
 
-    monitor_data_init(&hmp);
-    hmp.skip_flush = true;
+    monitor_data_init(&hmp, true);
 
     old_mon = cur_mon;
     cur_mon = &hmp;
@@ -4088,7 +4088,7 @@ void monitor_init(Chardev *chr, int flags)
     }
 
     mon = g_malloc(sizeof(*mon));
-    monitor_data_init(mon);
+    monitor_data_init(mon, false);
 
     qemu_chr_fe_init(&mon->chr, chr, &error_abort);
     mon->flags = flags;
-- 
2.14.3

[Qemu-devel] [PATCH v7 06/23] monitor: move the cur_mon hack deeper for QMP

[Peter Xu]

In monitor_qmp_read(), we have the hack to temporarily replace the
cur_mon pointer.  Now we move this hack deeper inside the QMP dispatcher
routine since the Monitor pointer can be actually obtained using
container_of() upon the parser object, just like most of the other JSON
parser users do.

This does not make much sense as a single patch.  However, this will be
a big step for the next patch, when the QMP dispatcher routine will be
split from the QMP parser.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/monitor.c b/monitor.c
index 3a28a6d935..253be6871a 100644
--- a/monitor.c
+++ b/monitor.c
@@ -3811,7 +3811,9 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
 {
     QObject *req, *rsp = NULL, *id = NULL;
     QDict *qdict = NULL;
-    Monitor *mon = cur_mon;
+    MonitorQMP *mon_qmp = container_of(parser, MonitorQMP, parser);
+    Monitor *old_mon, *mon = container_of(mon_qmp, Monitor, qmp);
+
     Error *err = NULL;
 
     req = json_parser_parse_err(tokens, NULL, &err);
@@ -3836,8 +3838,13 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
         QDECREF(req_json);
     }
 
+    old_mon = cur_mon;
+    cur_mon = mon;
+
     rsp = qmp_dispatch(cur_mon->qmp.commands, req);
 
+    cur_mon = old_mon;
+
     if (mon->qmp.commands == &qmp_cap_negotiation_commands) {
         qdict = qdict_get_qdict(qobject_to_qdict(rsp), "error");
         if (qdict
@@ -3874,13 +3881,9 @@ err_out:
 
 static void monitor_qmp_read(void *opaque, const uint8_t *buf, int size)
 {
-    Monitor *old_mon = cur_mon;
-
-    cur_mon = opaque;
-
-    json_message_parser_feed(&cur_mon->qmp.parser, (const char *) buf, size);
+    Monitor *mon = opaque;
 
-    cur_mon = old_mon;
+    json_message_parser_feed(&mon->qmp.parser, (const char *) buf, size);
 }
 
 static void monitor_read(void *opaque, const uint8_t *buf, int size)
-- 
2.14.3

[Qemu-devel] [PATCH v7 07/23] monitor: unify global init

[Peter Xu]

There are many places where the monitor initializes its globals:

- monitor_init_qmp_commands() at the very beginning
- single function to init monitor_lock
- in the first entry of monitor_init() using "is_first_init"

Unify them a bit.

monitor_lock is not used before monitor_init() (as confirmed by code
analysis and gdb watchpoints); so we are safe delaying what was a
constructor-time initialization of the mutex into the later first call
to monitor_init().

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/monitor/monitor.h |  2 +-
 monitor.c                 | 25 ++++++++++---------------
 vl.c                      |  7 ++++++-
 3 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/include/monitor/monitor.h b/include/monitor/monitor.h
index 83ea4a1aaf..3a5128ab1b 100644
--- a/include/monitor/monitor.h
+++ b/include/monitor/monitor.h
@@ -16,7 +16,7 @@ extern Monitor *cur_mon;
 
 bool monitor_cur_is_qmp(void);
 
-void monitor_init_qmp_commands(void);
+void monitor_init_globals(void);
 void monitor_init(Chardev *chr, int flags);
 void monitor_cleanup(void);
 
diff --git a/monitor.c b/monitor.c
index 253be6871a..f32187b991 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1000,7 +1000,7 @@ static void qmp_unregister_commands_hack(void)
 #endif
 }
 
-void monitor_init_qmp_commands(void)
+static void monitor_init_qmp_commands(void)
 {
     /*
      * Two command lists:
@@ -4034,6 +4034,14 @@ static void sortcmdlist(void)
     qsort((void *)info_cmds, array_num, elem_size, compare_mon_cmd);
 }
 
+void monitor_init_globals(void)
+{
+    monitor_init_qmp_commands();
+    monitor_qapi_event_init();
+    sortcmdlist();
+    qemu_mutex_init(&monitor_lock);
+}
+
 /* These functions just adapt the readline interface in a typesafe way.  We
  * could cast function pointers but that discards compiler checks.
  */
@@ -4074,23 +4082,10 @@ void error_vprintf_unless_qmp(const char *fmt, va_list ap)
     }
 }
 
-static void __attribute__((constructor)) monitor_lock_init(void)
-{
-    qemu_mutex_init(&monitor_lock);
-}
-
 void monitor_init(Chardev *chr, int flags)
 {
-    static int is_first_init = 1;
-    Monitor *mon;
-
-    if (is_first_init) {
-        monitor_qapi_event_init();
-        sortcmdlist();
-        is_first_init = 0;
-    }
+    Monitor *mon = g_malloc(sizeof(*mon));
 
-    mon = g_malloc(sizeof(*mon));
     monitor_data_init(mon, false);
 
     qemu_chr_fe_init(&mon->chr, chr, &error_abort);
diff --git a/vl.c b/vl.c
index e725ecbc08..095769e6c9 100644
--- a/vl.c
+++ b/vl.c
@@ -3098,7 +3098,6 @@ int main(int argc, char **argv, char **envp)
     qemu_init_exec_dir(argv[0]);
 
     module_call_init(MODULE_INIT_QOM);
-    monitor_init_qmp_commands();
 
     qemu_add_opts(&qemu_drive_opts);
     qemu_add_drive_opts(&qemu_legacy_drive_opts);
@@ -4562,6 +4561,12 @@ int main(int argc, char **argv, char **envp)
     default_drive(default_floppy, snapshot, IF_FLOPPY, 0, FD_OPTS);
     default_drive(default_sdcard, snapshot, IF_SD, 0, SD_OPTS);
 
+    /*
+     * Note: qtest_enabled() (which is used in monitor_qapi_event_init())
+     * depends on configure_accelerator() above.
+     */
+    monitor_init_globals();
+
     if (qemu_opts_foreach(qemu_find_opts("mon"),
                           mon_init_func, NULL, NULL)) {
         exit(1);
-- 
2.14.3

[Qemu-devel] [PATCH v7 08/23] monitor: let mon_list be tail queue

[Peter Xu]

It was QLIST.  I want to use this list to do monitor priority job later,
which need tail insertion ability.  So switching to a tail queue.

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/monitor.c b/monitor.c
index f32187b991..cef71d5c45 100644
--- a/monitor.c
+++ b/monitor.c
@@ -204,7 +204,7 @@ struct Monitor {
     void *password_opaque;
     mon_cmd_t *cmd_table;
     QLIST_HEAD(,mon_fd_t) fds;
-    QLIST_ENTRY(Monitor) entry;
+    QTAILQ_ENTRY(Monitor) entry;
 };
 
 /* QMP checker flags */
@@ -213,7 +213,7 @@ struct Monitor {
 /* Protects mon_list, monitor_event_state.  */
 static QemuMutex monitor_lock;
 
-static QLIST_HEAD(mon_list, Monitor) mon_list;
+static QTAILQ_HEAD(mon_list, Monitor) mon_list;
 static QLIST_HEAD(mon_fdsets, MonFdset) mon_fdsets;
 static int mon_refcount;
 
@@ -414,7 +414,7 @@ static void monitor_qapi_event_emit(QAPIEvent event, QDict *qdict)
     Monitor *mon;
 
     trace_monitor_protocol_event_emit(event, qdict);
-    QLIST_FOREACH(mon, &mon_list, entry) {
+    QTAILQ_FOREACH(mon, &mon_list, entry) {
         if (monitor_is_qmp(mon)
             && mon->qmp.commands != &qmp_cap_negotiation_commands) {
             monitor_json_emitter(mon, QOBJECT(qdict));
@@ -4109,7 +4109,7 @@ void monitor_init(Chardev *chr, int flags)
     }
 
     qemu_mutex_lock(&monitor_lock);
-    QLIST_INSERT_HEAD(&mon_list, mon, entry);
+    QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
     qemu_mutex_unlock(&monitor_lock);
 }
 
@@ -4118,8 +4118,8 @@ void monitor_cleanup(void)
     Monitor *mon, *next;
 
     qemu_mutex_lock(&monitor_lock);
-    QLIST_FOREACH_SAFE(mon, &mon_list, entry, next) {
-        QLIST_REMOVE(mon, entry);
+    QTAILQ_FOREACH_SAFE(mon, &mon_list, entry, next) {
+        QTAILQ_REMOVE(&mon_list, mon, entry);
         monitor_data_destroy(mon);
         g_free(mon);
     }
-- 
2.14.3

[Qemu-devel] [PATCH v7 09/23] monitor: allow using IO thread for parsing

[Peter Xu]

For each Monitor, add one field "use_io_thr" to show whether it will be
using the dedicated monitor IO thread to handle input/output.  When set,
monitor IO parsing work will be offloaded to the dedicated monitor IO
thread, rather than the original main loop thread.

This only works for QMP.  HMP will always be run on the main loop
thread.

Currently we're still keeping use_io_thr off always.  Will turn it on
later at some point.

One thing to mention is that we cannot set use_io_thr for every QMP
monitor.  The problem is that MUXed typed chardevs may not work well
with it now. When MUX is used, frontend of chardev can be the monitor
plus something else.  The only thing we know would be safe to be run
outside main thread so far is the monitor frontend. All the rest of the
frontends should still be run in main thread only.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 107 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 99 insertions(+), 8 deletions(-)

diff --git a/monitor.c b/monitor.c
index cef71d5c45..fd6e9a6d28 100644
--- a/monitor.c
+++ b/monitor.c
@@ -35,6 +35,7 @@
 #include "net/net.h"
 #include "net/slirp.h"
 #include "chardev/char-fe.h"
+#include "chardev/char-io.h"
 #include "ui/qemu-spice.h"
 #include "sysemu/numa.h"
 #include "monitor/monitor.h"
@@ -75,6 +76,7 @@
 #include "qmp-introspect.h"
 #include "sysemu/qtest.h"
 #include "sysemu/cpus.h"
+#include "sysemu/iothread.h"
 #include "qemu/cutils.h"
 #include "qapi/qmp/dispatch.h"
 
@@ -189,6 +191,7 @@ struct Monitor {
     int flags;
     int suspend_cnt;
     bool skip_flush;
+    bool use_io_thr;
 
     QemuMutex out_lock;
     QString *outbuf;
@@ -207,6 +210,11 @@ struct Monitor {
     QTAILQ_ENTRY(Monitor) entry;
 };
 
+/* Let's add monitor global variables to this struct. */
+static struct {
+    IOThread *mon_iothread;
+} mon_global;
+
 /* QMP checker flags */
 #define QMP_ACCEPT_UNKNOWNS 1
 
@@ -567,7 +575,8 @@ static void monitor_qapi_event_init(void)
 
 static void handle_hmp_command(Monitor *mon, const char *cmdline);
 
-static void monitor_data_init(Monitor *mon, bool skip_flush)
+static void monitor_data_init(Monitor *mon, bool skip_flush,
+                              bool use_io_thr)
 {
     memset(mon, 0, sizeof(Monitor));
     qemu_mutex_init(&mon->out_lock);
@@ -575,6 +584,7 @@ static void monitor_data_init(Monitor *mon, bool skip_flush)
     /* Use *mon_cmds by default. */
     mon->cmd_table = mon_cmds;
     mon->skip_flush = skip_flush;
+    mon->use_io_thr = use_io_thr;
 }
 
 static void monitor_data_destroy(Monitor *mon)
@@ -595,7 +605,7 @@ char *qmp_human_monitor_command(const char *command_line, bool has_cpu_index,
     char *output = NULL;
     Monitor *old_mon, hmp;
 
-    monitor_data_init(&hmp, true);
+    monitor_data_init(&hmp, true, false);
 
     old_mon = cur_mon;
     cur_mon = &hmp;
@@ -4034,12 +4044,29 @@ static void sortcmdlist(void)
     qsort((void *)info_cmds, array_num, elem_size, compare_mon_cmd);
 }
 
+static GMainContext *monitor_io_context_get(void)
+{
+    return iothread_get_g_main_context(mon_global.mon_iothread);
+}
+
+static AioContext *monitor_aio_context_get(void)
+{
+    return iothread_get_aio_context(mon_global.mon_iothread);
+}
+
+static void monitor_iothread_init(void)
+{
+    mon_global.mon_iothread = iothread_create("mon_iothread",
+                                              &error_abort);
+}
+
 void monitor_init_globals(void)
 {
     monitor_init_qmp_commands();
     monitor_qapi_event_init();
     sortcmdlist();
     qemu_mutex_init(&monitor_lock);
+    monitor_iothread_init();
 }
 
 /* These functions just adapt the readline interface in a typesafe way.  We
@@ -4082,11 +4109,41 @@ void error_vprintf_unless_qmp(const char *fmt, va_list ap)
     }
 }
 
+static void monitor_list_append(Monitor *mon)
+{
+    qemu_mutex_lock(&monitor_lock);
+    QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
+    qemu_mutex_unlock(&monitor_lock);
+}
+
+static void monitor_qmp_setup_handlers(void *data)
+{
+    Monitor *mon = data;
+    GMainContext *context;
+
+    if (mon->use_io_thr) {
+        /*
+         * When use_io_thr is set, we use the global shared dedicated
+         * IO thread for this monitor to handle input/output.
+         */
+        context = monitor_io_context_get();
+        /* We should have inited globals before reaching here. */
+        assert(context);
+    } else {
+        /* The default main loop, which is the main thread */
+        context = NULL;
+    }
+
+    qemu_chr_fe_set_handlers(&mon->chr, monitor_can_read, monitor_qmp_read,
+                             monitor_qmp_event, NULL, mon, context, true);
+    monitor_list_append(mon);
+}
+
 void monitor_init(Chardev *chr, int flags)
 {
     Monitor *mon = g_malloc(sizeof(*mon));
 
-    monitor_data_init(mon, false);
+    monitor_data_init(mon, false, false);
 
     qemu_chr_fe_init(&mon->chr, chr, &error_abort);
     mon->flags = flags;
@@ -4099,24 +4156,55 @@ void monitor_init(Chardev *chr, int flags)
     }
 
     if (monitor_is_qmp(mon)) {
-        qemu_chr_fe_set_handlers(&mon->chr, monitor_can_read, monitor_qmp_read,
-                                 monitor_qmp_event, NULL, mon, NULL, true);
         qemu_chr_fe_set_echo(&mon->chr, true);
         json_message_parser_init(&mon->qmp.parser, handle_qmp_command);
+        if (mon->use_io_thr) {
+            /*
+             * It's possible that we already have an IOWatchPoll
+             * registered for the Chardev during chardev_init_func().
+             * When that happened, the gcontext was still the default
+             * main context, always.  We need to make sure we
+             * unregister that first and from now on we run the
+             * chardev on the new gcontext.
+             */
+            remove_fd_in_watch(chr);
+            /*
+             * We can't call qemu_chr_fe_set_handlers() directly here
+             * since during the procedure the chardev will be active
+             * and running in monitor iothread, while we'll still do
+             * something before returning from it, which is a possible
+             * race too.  To avoid that, we just create a BH to setup
+             * the handlers.
+             */
+            aio_bh_schedule_oneshot(monitor_aio_context_get(),
+                                    monitor_qmp_setup_handlers, mon);
+            /* We'll add this to mon_list in the BH when setup done */
+            return;
+        } else {
+            qemu_chr_fe_set_handlers(&mon->chr, monitor_can_read,
+                                     monitor_qmp_read, monitor_qmp_event,
+                                     NULL, mon, NULL, true);
+        }
     } else {
         qemu_chr_fe_set_handlers(&mon->chr, monitor_can_read, monitor_read,
                                  monitor_event, NULL, mon, NULL, true);
     }
 
-    qemu_mutex_lock(&monitor_lock);
-    QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
-    qemu_mutex_unlock(&monitor_lock);
+    monitor_list_append(mon);
 }
 
 void monitor_cleanup(void)
 {
     Monitor *mon, *next;
 
+    /*
+     * We need to explicitly stop the iothread (but not destroy it),
+     * cleanup the monitor resources, then destroy the iothread since
+     * we need to unregister from chardev below in
+     * monitor_data_destroy(), and chardev is not thread-safe yet
+     */
+    iothread_stop(mon_global.mon_iothread);
+
     qemu_mutex_lock(&monitor_lock);
     QTAILQ_FOREACH_SAFE(mon, &mon_list, entry, next) {
         QTAILQ_REMOVE(&mon_list, mon, entry);
@@ -4124,6 +4212,9 @@ void monitor_cleanup(void)
         g_free(mon);
     }
     qemu_mutex_unlock(&monitor_lock);
+
+    iothread_destroy(mon_global.mon_iothread);
+    mon_global.mon_iothread = NULL;
 }
 
 QemuOptsList qemu_mon_opts = {
-- 
2.14.3

[Qemu-devel] [PATCH v7 10/23] qmp: introduce QMPCapability

[Peter Xu]

There were no QMP capabilities defined.  Define the first "oob" as
capability to allow out-of-band messages.

After this patch, we will allow QMP clients to enable QMP capabilities
when sending the first "qmp_capabilities" command.  Originally we are
starting QMP session with no arguments like:

  { "execute": "qmp_capabilities" }

Now we can enable some QMP capabilities using (take OOB as example,
which is the only one capability that we support):

  { "execute": "qmp_capabilities",
    "argument": { "enable": [ "oob" ] } }

When the "argument" key is not provided, no capability is enabled.

For capability "oob", the monitor needs to be run on dedicated IO
thread, otherwise the command will fail.  For example, trying to enable
OOB on a MUXed typed QMP monitor will fail.

One thing to mention is that, QMP capabilities are per-monitor, and also
when the connection is closed due to some reason, the capabilities will
be reset.

Also, touch up qmp-test.c to test the new bits.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c        | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
 qapi-schema.json | 32 +++++++++++++++++++++---
 tests/qmp-test.c | 10 +++++++-
 3 files changed, 109 insertions(+), 9 deletions(-)

diff --git a/monitor.c b/monitor.c
index fd6e9a6d28..3e07798442 100644
--- a/monitor.c
+++ b/monitor.c
@@ -167,6 +167,7 @@ typedef struct {
      * mode.
      */
     QmpCommandList *commands;
+    bool qmp_caps[QMP_CAPABILITY__MAX];
 } MonitorQMP;
 
 /*
@@ -1036,8 +1037,42 @@ static void monitor_init_qmp_commands(void)
                          qmp_marshal_qmp_capabilities, QCO_NO_OPTIONS);
 }
 
-void qmp_qmp_capabilities(Error **errp)
+static void qmp_caps_check(Monitor *mon, QMPCapabilityList *list,
+                           Error **errp)
+{
+    for (; list; list = list->next) {
+        assert(list->value < QMP_CAPABILITY__MAX);
+        switch (list->value) {
+        case QMP_CAPABILITY_OOB:
+            if (!mon->use_io_thr) {
+                /*
+                 * Out-Of-Band only works with monitors that are
+                 * running on dedicated IOThread.
+                 */
+                error_setg(errp, "This monitor does not support "
+                           "Out-Of-Band (OOB)");
+                return;
+            }
+            break;
+        default:
+            break;
+        }
+    }
+}
+
+/* This function should only be called after capabilities are checked. */
+static void qmp_caps_apply(Monitor *mon, QMPCapabilityList *list)
 {
+    for (; list; list = list->next) {
+        mon->qmp.qmp_caps[list->value] = true;
+    }
+}
+
+void qmp_qmp_capabilities(bool has_enable, QMPCapabilityList *enable,
+                          Error **errp)
+{
+    Error *local_err = NULL;
+
     if (cur_mon->qmp.commands == &qmp_commands) {
         error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
                   "Capabilities negotiation is already complete, command "
@@ -1045,6 +1080,21 @@ void qmp_qmp_capabilities(Error **errp)
         return;
     }
 
+    /* Enable QMP capabilities provided by the client if applicable. */
+    if (has_enable) {
+        qmp_caps_check(cur_mon, enable, &local_err);
+        if (local_err) {
+            /*
+             * Failed check on any of the capabilities will fail the
+             * entire command (and thus not apply any of the other
+             * capabilities that were also requested).
+             */
+            error_propagate(errp, local_err);
+            return;
+        }
+        qmp_caps_apply(cur_mon, enable);
+    }
+
     cur_mon->qmp.commands = &qmp_commands;
 }
 
@@ -3942,14 +3992,29 @@ void monitor_resume(Monitor *mon)
         readline_show_prompt(mon->rs);
 }
 
-static QObject *get_qmp_greeting(void)
+static QObject *get_qmp_greeting(Monitor *mon)
 {
+    QList *cap_list = qlist_new();
     QObject *ver = NULL;
+    QMPCapability cap;
 
     qmp_marshal_query_version(NULL, &ver, NULL);
 
-    return qobject_from_jsonf("{'QMP': {'version': %p, 'capabilities': []}}",
-                              ver);
+    for (cap = 0; cap < QMP_CAPABILITY__MAX; cap++) {
+        if (!mon->use_io_thr && cap == QMP_CAPABILITY_OOB) {
+            /* Monitors that are not using IOThread won't support OOB */
+            continue;
+        }
+        qlist_append(cap_list, qstring_from_str(QMPCapability_str(cap)));
+    }
+
+    return qobject_from_jsonf("{'QMP': {'version': %p, 'capabilities': %p}}",
+                              ver, cap_list);
+}
+
+static void monitor_qmp_caps_reset(Monitor *mon)
+{
+    memset(mon->qmp.qmp_caps, 0, sizeof(mon->qmp.qmp_caps));
 }
 
 static void monitor_qmp_event(void *opaque, int event)
@@ -3960,7 +4025,8 @@ static void monitor_qmp_event(void *opaque, int event)
     switch (event) {
     case CHR_EVENT_OPENED:
         mon->qmp.commands = &qmp_cap_negotiation_commands;
-        data = get_qmp_greeting();
+        monitor_qmp_caps_reset(mon);
+        data = get_qmp_greeting(mon);
         monitor_json_emitter(mon, data);
         qobject_decref(data);
         mon_refcount++;
diff --git a/qapi-schema.json b/qapi-schema.json
index 5c06745c79..2490d5188e 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -102,21 +102,47 @@
 #
 # Enable QMP capabilities.
 #
-# Arguments: None.
+# Arguments:
+#
+# @enable:    List of QMPCapabilities to enable, which is optional.
+#             Client must not enable any capability that is not
+#             mentioned in QMP greeting message.  If the field is not
+#             provided, it means no QMP capabilities will be enabled.
+#             (since 2.12)
 #
 # Example:
 #
-# -> { "execute": "qmp_capabilities" }
+# -> { "execute": "qmp_capabilities",
+#      "arguments": { "enable": [ "oob" ] } }
 # <- { "return": {} }
 #
 # Notes: This command is valid exactly when first connecting: it must be
 # issued before any other command will be accepted, and will fail once the
 # monitor is accepting other commands. (see qemu docs/interop/qmp-spec.txt)
 #
+# QMP client needs to explicitly enable QMP capabilities, otherwise
+# all the QMP capabilities will be turned off by default.
+#
 # Since: 0.13
 #
 ##
-{ 'command': 'qmp_capabilities' }
+{ 'command': 'qmp_capabilities',
+  'data': { '*enable': [ 'QMPCapability' ] } }
+
+##
+# @QMPCapability:
+#
+# Enumeration of capabilities to be advertised during initial client
+# connection, used for agreeing on particular QMP extension behaviors.
+#
+# @oob:   QMP ability to support Out-Of-Band requests.
+#         (Please refer to qmp-spec.txt for more information on OOB)
+#
+# Since: 2.12
+#
+##
+{ 'enum': 'QMPCapability',
+  'data': [ 'oob' ] }
 
 ##
 # @VersionTriple:
diff --git a/tests/qmp-test.c b/tests/qmp-test.c
index 36feb2204b..11b384c829 100644
--- a/tests/qmp-test.c
+++ b/tests/qmp-test.c
@@ -17,6 +17,7 @@
 #include "qapi/qobject-input-visitor.h"
 #include "qapi/util.h"
 #include "qapi/visitor.h"
+#include "qapi/qmp/qstring.h"
 
 const char common_args[] = "-nodefaults -machine none";
 
@@ -75,6 +76,8 @@ static void test_qmp_protocol(void)
 {
     QDict *resp, *q, *ret;
     QList *capabilities;
+    const QListEntry *entry;
+    QString *qstr;
 
     global_qtest = qtest_init_without_qmp_handshake(common_args);
 
@@ -84,7 +87,12 @@ static void test_qmp_protocol(void)
     g_assert(q);
     test_version(qdict_get(q, "version"));
     capabilities = qdict_get_qlist(q, "capabilities");
-    g_assert(capabilities && qlist_empty(capabilities));
+    g_assert(capabilities);
+    entry = qlist_first(capabilities);
+    g_assert(entry);
+    qstr = qobject_to_qstring(entry->value);
+    g_assert(qstr);
+    g_assert_cmpstr(qstring_get_str(qstr), ==, "oob");
     QDECREF(resp);
 
     /* Test valid command before handshake */
-- 
2.14.3

[Qemu-devel] [PATCH v7 11/23] monitor: introduce monitor_qmp_respond()

[Peter Xu]

A tiny refactoring, preparing to split the QMP dispatcher away.

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 50 +++++++++++++++++++++++++++++++++-----------------
 1 file changed, 33 insertions(+), 17 deletions(-)

diff --git a/monitor.c b/monitor.c
index 3e07798442..92114aaa80 100644
--- a/monitor.c
+++ b/monitor.c
@@ -3867,6 +3867,38 @@ static int monitor_can_read(void *opaque)
     return (mon->suspend_cnt == 0) ? 1 : 0;
 }
 
+/*
+ * 1. This function takes ownership of rsp, err, and id.
+ * 2. rsp, err, and id may be NULL.
+ * 3. If err != NULL then rsp must be NULL.
+ */
+static void monitor_qmp_respond(Monitor *mon, QObject *rsp,
+                                Error *err, QObject *id)
+{
+    QDict *qdict = NULL;
+
+    if (err) {
+        assert(!rsp);
+        qdict = qdict_new();
+        qdict_put_obj(qdict, "error", qmp_build_error_object(err));
+        error_free(err);
+        rsp = QOBJECT(qdict);
+    }
+
+    if (rsp) {
+        if (id) {
+            /* This is for the qdict below. */
+            qobject_incref(id);
+            qdict_put_obj(qobject_to_qdict(rsp), "id", id);
+        }
+
+        monitor_json_emitter(mon, rsp);
+    }
+
+    qobject_decref(id);
+    qobject_decref(rsp);
+}
+
 static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
 {
     QObject *req, *rsp = NULL, *id = NULL;
@@ -3918,24 +3950,8 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
     }
 
 err_out:
-    if (err) {
-        qdict = qdict_new();
-        qdict_put_obj(qdict, "error", qmp_build_error_object(err));
-        error_free(err);
-        rsp = QOBJECT(qdict);
-    }
+    monitor_qmp_respond(mon, rsp, err, id);
 
-    if (rsp) {
-        if (id) {
-            qdict_put_obj(qobject_to_qdict(rsp), "id", id);
-            id = NULL;
-        }
-
-        monitor_json_emitter(mon, rsp);
-    }
-
-    qobject_decref(id);
-    qobject_decref(rsp);
     qobject_decref(req);
 }
 
-- 
2.14.3

[Qemu-devel] [PATCH v7 12/23] monitor: let suspend_cnt be thread safe

[Peter Xu]

Monitor code now can be run in more than one thread.  Let it be thread
safe when accessing suspend_cnt counter.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/monitor.c b/monitor.c
index 92114aaa80..60bcf67b3a 100644
--- a/monitor.c
+++ b/monitor.c
@@ -190,7 +190,7 @@ struct Monitor {
     CharBackend chr;
     int reset_seen;
     int flags;
-    int suspend_cnt;
+    int suspend_cnt;            /* Needs to be accessed atomically */
     bool skip_flush;
     bool use_io_thr;
 
@@ -3864,7 +3864,7 @@ static int monitor_can_read(void *opaque)
 {
     Monitor *mon = opaque;
 
-    return (mon->suspend_cnt == 0) ? 1 : 0;
+    return !atomic_mb_read(&mon->suspend_cnt);
 }
 
 /*
@@ -3996,7 +3996,7 @@ int monitor_suspend(Monitor *mon)
 {
     if (!mon->rs)
         return -ENOTTY;
-    mon->suspend_cnt++;
+    atomic_inc(&mon->suspend_cnt);
     return 0;
 }
 
@@ -4004,8 +4004,9 @@ void monitor_resume(Monitor *mon)
 {
     if (!mon->rs)
         return;
-    if (--mon->suspend_cnt == 0)
+    if (atomic_dec_fetch(&mon->suspend_cnt) == 0) {
         readline_show_prompt(mon->rs);
+    }
 }
 
 static QObject *get_qmp_greeting(Monitor *mon)
@@ -4070,19 +4071,19 @@ static void monitor_event(void *opaque, int event)
             monitor_resume(mon);
             monitor_flush(mon);
         } else {
-            mon->suspend_cnt = 0;
+            atomic_mb_set(&mon->suspend_cnt, 0);
         }
         break;
 
     case CHR_EVENT_MUX_OUT:
         if (mon->reset_seen) {
-            if (mon->suspend_cnt == 0) {
+            if (atomic_mb_read(&mon->suspend_cnt) == 0) {
                 monitor_printf(mon, "\n");
             }
             monitor_flush(mon);
             monitor_suspend(mon);
         } else {
-            mon->suspend_cnt++;
+            atomic_inc(&mon->suspend_cnt);
         }
         qemu_mutex_lock(&mon->out_lock);
         mon->mux_out = 1;
-- 
2.14.3

[Qemu-devel] [PATCH v7 13/23] monitor: let suspend/resume work even with QMPs

[Peter Xu]

This patches allows QMP monitors to be suspended/resumed.

One thing to mention is that for QMPs that are using IOThreads, we need
an explicit kick for the IOThread in case it is sleeping.

Meanwhile, we need to take special care on non-interactive HMPs.
Currently only gdbserver is using that.  For these monitors, we still
don't allow suspend/resume operations.

Since at it, add traces for the operations.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c    | 45 ++++++++++++++++++++++++++++++++++++++++++---
 trace-events |  1 +
 2 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/monitor.c b/monitor.c
index 60bcf67b3a..76137ba2a4 100644
--- a/monitor.c
+++ b/monitor.c
@@ -246,6 +246,21 @@ static inline bool monitor_is_qmp(const Monitor *mon)
     return (mon->flags & MONITOR_USE_CONTROL);
 }
 
+/**
+ * Whether @mon is using readline?  Note: not all HMP monitors can are
+ * using readline, e.g., gdbserver has non-interactive HMP monitor, so
+ * readline is not used there.
+ */
+static inline bool monitor_uses_readline(const Monitor *mon)
+{
+    return mon->flags & MONITOR_USE_READLINE;
+}
+
+static inline bool monitor_is_hmp_non_interactive(const Monitor *mon)
+{
+    return !monitor_is_qmp(mon) && !monitor_uses_readline(mon);
+}
+
 /**
  * Is the current monitor, if any, a QMP monitor?
  */
@@ -3994,19 +4009,43 @@ static void monitor_command_cb(void *opaque, const char *cmdline,
 
 int monitor_suspend(Monitor *mon)
 {
-    if (!mon->rs)
+    if (monitor_is_hmp_non_interactive(mon)) {
         return -ENOTTY;
+    }
+
+    if (monitor_is_qmp(mon)) {
+        /*
+         * Kick iothread to make sure this takes effect.  It'll be
+         * evaluated again in prepare() of the watch object.
+         */
+        aio_notify(iothread_get_aio_context(mon_global.mon_iothread));
+    }
     atomic_inc(&mon->suspend_cnt);
+    trace_monitor_suspend(mon, 1);
     return 0;
 }
 
 void monitor_resume(Monitor *mon)
 {
-    if (!mon->rs)
+    if (monitor_is_hmp_non_interactive(mon)) {
         return;
+    }
+
     if (atomic_dec_fetch(&mon->suspend_cnt) == 0) {
-        readline_show_prompt(mon->rs);
+        if (monitor_is_qmp(mon)) {
+            /*
+             * For QMP monitors that are running in IOThread, let's
+             * kick the thread in case it's sleeping.
+             */
+            if (mon->use_io_thr) {
+                aio_notify(iothread_get_aio_context(mon_global.mon_iothread));
+            }
+        } else {
+            assert(mon->rs);
+            readline_show_prompt(mon->rs);
+        }
     }
+    trace_monitor_suspend(mon, -1);
 }
 
 static QObject *get_qmp_greeting(Monitor *mon)
diff --git a/trace-events b/trace-events
index ec95e67089..eecb68b1d5 100644
--- a/trace-events
+++ b/trace-events
@@ -47,6 +47,7 @@ monitor_protocol_event_emit(uint32_t event, void *data) "event=%d data=%p"
 monitor_protocol_event_queue(uint32_t event, void *qdict, uint64_t rate) "event=%d data=%p rate=%" PRId64
 handle_hmp_command(void *mon, const char *cmdline) "mon %p cmdline: %s"
 handle_qmp_command(void *mon, const char *req) "mon %p req: %s"
+monitor_suspend(void *ptr, int cnt) "mon %p: %d"
 
 # dma-helpers.c
 dma_blk_io(void *dbs, void *bs, int64_t offset, bool to_dev) "dbs=%p bs=%p offset=%" PRId64 " to_dev=%d"
-- 
2.14.3

[Qemu-devel] [PATCH v7 14/23] monitor: separate QMP parser and dispatcher

[Peter Xu]

Originally QMP goes through these steps:

  JSON Parser --> QMP Dispatcher --> Respond
      /|\    (2)                (3)     |
   (1) |                               \|/ (4)
       +---------  main thread  --------+

This patch does this:

  JSON Parser     QMP Dispatcher --> Respond
      /|\ |           /|\       (4)     |
       |  | (2)        | (3)            |  (5)
   (1) |  +----->      |               \|/
       +---------  main thread  <-------+

So the parsing job and the dispatching job is isolated now.  It gives us
a chance in following up patches to totally move the parser outside.

The isolation is done using one QEMUBH. Only one dispatcher QEMUBH is
used for all the monitors.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 201 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 178 insertions(+), 23 deletions(-)

diff --git a/monitor.c b/monitor.c
index 76137ba2a4..51d12412fa 100644
--- a/monitor.c
+++ b/monitor.c
@@ -168,6 +168,13 @@ typedef struct {
      */
     QmpCommandList *commands;
     bool qmp_caps[QMP_CAPABILITY__MAX];
+    /*
+     * Protects qmp request/response queue.  Please take monitor_lock
+     * first when used together.
+     */
+    QemuMutex qmp_queue_lock;
+    /* Input queue that holds all the parsed QMP requests */
+    GQueue *qmp_requests;
 } MonitorQMP;
 
 /*
@@ -214,6 +221,8 @@ struct Monitor {
 /* Let's add monitor global variables to this struct. */
 static struct {
     IOThread *mon_iothread;
+    /* Bottom half to dispatch the requests received from IO thread */
+    QEMUBH *qmp_dispatcher_bh;
 } mon_global;
 
 /* QMP checker flags */
@@ -596,11 +605,13 @@ static void monitor_data_init(Monitor *mon, bool skip_flush,
 {
     memset(mon, 0, sizeof(Monitor));
     qemu_mutex_init(&mon->out_lock);
+    qemu_mutex_init(&mon->qmp.qmp_queue_lock);
     mon->outbuf = qstring_new();
     /* Use *mon_cmds by default. */
     mon->cmd_table = mon_cmds;
     mon->skip_flush = skip_flush;
     mon->use_io_thr = use_io_thr;
+    mon->qmp.qmp_requests = g_queue_new();
 }
 
 static void monitor_data_destroy(Monitor *mon)
@@ -613,6 +624,8 @@ static void monitor_data_destroy(Monitor *mon)
     readline_free(mon->rs);
     QDECREF(mon->outbuf);
     qemu_mutex_destroy(&mon->out_lock);
+    qemu_mutex_destroy(&mon->qmp.qmp_queue_lock);
+    g_queue_free(mon->qmp.qmp_requests);
 }
 
 char *qmp_human_monitor_command(const char *command_line, bool has_cpu_index,
@@ -1052,6 +1065,16 @@ static void monitor_init_qmp_commands(void)
                          qmp_marshal_qmp_capabilities, QCO_NO_OPTIONS);
 }
 
+static bool qmp_cap_enabled(Monitor *mon, QMPCapability cap)
+{
+    return mon->qmp.qmp_caps[cap];
+}
+
+static bool qmp_oob_enabled(Monitor *mon)
+{
+    return qmp_cap_enabled(mon, QMP_CAPABILITY_OOB);
+}
+
 static void qmp_caps_check(Monitor *mon, QMPCapabilityList *list,
                            Error **errp)
 {
@@ -3914,30 +3937,39 @@ static void monitor_qmp_respond(Monitor *mon, QObject *rsp,
     qobject_decref(rsp);
 }
 
-static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
+struct QMPRequest {
+    /* Owner of the request */
+    Monitor *mon;
+    /* "id" field of the request */
+    QObject *id;
+    /* Request object to be handled */
+    QObject *req;
+    /*
+     * Whether we need to resume the monitor afterward.  This flag is
+     * used to emulate the old QMP server behavior that the current
+     * command must be completed before execution of the next one.
+     */
+    bool need_resume;
+};
+typedef struct QMPRequest QMPRequest;
+
+/*
+ * Dispatch one single QMP request. The function will free the req_obj
+ * and objects inside it before return.
+ */
+static void monitor_qmp_dispatch_one(QMPRequest *req_obj)
 {
-    QObject *req, *rsp = NULL, *id = NULL;
+    Monitor *mon, *old_mon;
+    QObject *req, *rsp = NULL, *id;
     QDict *qdict = NULL;
-    MonitorQMP *mon_qmp = container_of(parser, MonitorQMP, parser);
-    Monitor *old_mon, *mon = container_of(mon_qmp, Monitor, qmp);
-
-    Error *err = NULL;
+    bool need_resume;
 
-    req = json_parser_parse_err(tokens, NULL, &err);
-    if (!req && !err) {
-        /* json_parser_parse_err() sucks: can fail without setting @err */
-        error_setg(&err, QERR_JSON_PARSING);
-    }
-    if (err) {
-        goto err_out;
-    }
+    req = req_obj->req;
+    mon = req_obj->mon;
+    id = req_obj->id;
+    need_resume = req_obj->need_resume;
 
-    qdict = qobject_to_qdict(req);
-    if (qdict) {
-        id = qdict_get(qdict, "id");
-        qobject_incref(id);
-        qdict_del(qdict, "id");
-    } /* else will fail qmp_dispatch() */
+    g_free(req_obj);
 
     if (trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
         QString *req_json = qobject_to_json(req);
@@ -3948,7 +3980,7 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
     old_mon = cur_mon;
     cur_mon = mon;
 
-    rsp = qmp_dispatch(cur_mon->qmp.commands, req);
+    rsp = qmp_dispatch(mon->qmp.commands, req);
 
     cur_mon = old_mon;
 
@@ -3964,12 +3996,122 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
         }
     }
 
-err_out:
-    monitor_qmp_respond(mon, rsp, err, id);
+    /* Respond if necessary */
+    monitor_qmp_respond(mon, rsp, NULL, id);
+
+    /* This pairs with the monitor_suspend() in handle_qmp_command(). */
+    if (need_resume) {
+        monitor_resume(mon);
+    }
 
     qobject_decref(req);
 }
 
+/*
+ * Pop one QMP request from monitor queues, return NULL if not found.
+ * We are using round-robin fashion to pop the request, to avoid
+ * processing command only on a very busy monitor.  To achieve that,
+ * when we processed one request on specific monitor, we put that
+ * monitor to the end of mon_list queue.
+ */
+static QMPRequest *monitor_qmp_requests_pop_one(void)
+{
+    QMPRequest *req_obj = NULL;
+    Monitor *mon;
+
+    qemu_mutex_lock(&monitor_lock);
+
+    QTAILQ_FOREACH(mon, &mon_list, entry) {
+        qemu_mutex_lock(&mon->qmp.qmp_queue_lock);
+        req_obj = g_queue_pop_head(mon->qmp.qmp_requests);
+        qemu_mutex_unlock(&mon->qmp.qmp_queue_lock);
+        if (req_obj) {
+            break;
+        }
+    }
+
+    if (req_obj) {
+        /*
+         * We found one request on the monitor. Degrade this monitor's
+         * priority to lowest by re-inserting it to end of queue.
+         */
+        QTAILQ_REMOVE(&mon_list, mon, entry);
+        QTAILQ_INSERT_TAIL(&mon_list, mon, entry);
+    }
+
+    qemu_mutex_unlock(&monitor_lock);
+
+    return req_obj;
+}
+
+static void monitor_qmp_bh_dispatcher(void *data)
+{
+    QMPRequest *req_obj = monitor_qmp_requests_pop_one();
+
+    if (req_obj) {
+        monitor_qmp_dispatch_one(req_obj);
+        /* Reschedule instead of looping so the main loop stays responsive */
+        qemu_bh_schedule(mon_global.qmp_dispatcher_bh);
+    }
+}
+
+static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
+{
+    QObject *req, *id = NULL;
+    QDict *qdict = NULL;
+    MonitorQMP *mon_qmp = container_of(parser, MonitorQMP, parser);
+    Monitor *mon = container_of(mon_qmp, Monitor, qmp);
+    Error *err = NULL;
+    QMPRequest *req_obj;
+
+    req = json_parser_parse_err(tokens, NULL, &err);
+    if (!req && !err) {
+        /* json_parser_parse_err() sucks: can fail without setting @err */
+        error_setg(&err, QERR_JSON_PARSING);
+    }
+    if (err) {
+        monitor_qmp_respond(mon, NULL, err, NULL);
+        qobject_decref(req);
+        return;
+    }
+
+    qdict = qobject_to_qdict(req);
+    if (qdict) {
+        id = qdict_get(qdict, "id");
+        qobject_incref(id);
+        qdict_del(qdict, "id");
+    } /* else will fail qmp_dispatch() */
+
+    req_obj = g_new0(QMPRequest, 1);
+    req_obj->mon = mon;
+    req_obj->id = id;
+    req_obj->req = req;
+    req_obj->need_resume = false;
+
+    /*
+     * If OOB is not enabled on current monitor, we'll emulate the old
+     * behavior that we won't process current monitor any more until
+     * it is responded.  This helps make sure that as long as OOB is
+     * not enabled, the server will never drop any command.
+     */
+    if (!qmp_oob_enabled(mon)) {
+        monitor_suspend(mon);
+        req_obj->need_resume = true;
+    }
+
+    /*
+     * Put the request to the end of queue so that requests will be
+     * handled in time order.  Ownership for req_obj, req, id,
+     * etc. will be delivered to the handler side.
+     */
+    qemu_mutex_lock(&mon->qmp.qmp_queue_lock);
+    g_queue_push_tail(mon->qmp.qmp_requests, req_obj);
+    qemu_mutex_unlock(&mon->qmp.qmp_queue_lock);
+
+    /* Kick the dispatcher routine */
+    qemu_bh_schedule(mon_global.qmp_dispatcher_bh);
+}
+
 static void monitor_qmp_read(void *opaque, const uint8_t *buf, int size)
 {
     Monitor *mon = opaque;
@@ -4180,6 +4322,15 @@ static void monitor_iothread_init(void)
 {
     mon_global.mon_iothread = iothread_create("mon_iothread",
                                               &error_abort);
+
+    /*
+     * This MUST be on main loop thread since we have commands that
+     * have assumption to be run on main loop thread.  It would be
+     * nice that one day we can remove this assumption in the future.
+     */
+    mon_global.qmp_dispatcher_bh = aio_bh_new(qemu_get_aio_context(),
+                                              monitor_qmp_bh_dispatcher,
+                                              NULL);
 }
 
 void monitor_init_globals(void)
@@ -4335,6 +4486,10 @@ void monitor_cleanup(void)
     }
     qemu_mutex_unlock(&monitor_lock);
 
+    /* QEMUBHs needs to be deleted before destroying the IOThread. */
+    qemu_bh_delete(mon_global.qmp_dispatcher_bh);
+    mon_global.qmp_dispatcher_bh = NULL;
+
     iothread_destroy(mon_global.mon_iothread);
     mon_global.mon_iothread = NULL;
 }
-- 
2.14.3

[Qemu-devel] [PATCH v7 15/23] qmp: add new event "command-dropped"

[Peter Xu]

This event will be emitted if one QMP command is dropped.  Along,
declare an enum for the reasons.

Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 qapi-schema.json | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/qapi-schema.json b/qapi-schema.json
index 2490d5188e..d6c89efc0d 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3215,3 +3215,40 @@
 # Since: 2.11
 ##
 { 'command': 'watchdog-set-action', 'data' : {'action': 'WatchdogAction'} }
+
+##
+# @CommandDropReason:
+#
+# Reasons that caused one command to be dropped.
+#
+# @queue-full: the command queue is full. This can only occur when
+#              the client sends a new non-oob command before the
+#              response to the previous non-oob command has been
+#              received.
+#
+# Since: 2.12
+##
+{ 'enum': 'CommandDropReason',
+  'data': [ 'queue-full' ] }
+
+##
+# @COMMAND_DROPPED:
+#
+# Emitted when a command is dropped due to some reason.  Commands can
+# only be dropped when the oob capability is enabled.
+#
+# @id: The dropped command's "id" field.
+#
+# @reason: The reason why the command is dropped.
+#
+# Since: 2.12
+#
+# Example:
+#
+# { "event": "COMMAND_DROPPED",
+#   "data": {"result": {"id": "libvirt-102",
+#                       "reason": "queue-full" } } }
+#
+##
+{ 'event': 'COMMAND_DROPPED' ,
+  'data': { 'id': 'any', 'reason': 'CommandDropReason' } }
-- 
2.14.3

[Qemu-devel] [PATCH v7 16/23] monitor: send event when command queue full

[Peter Xu]

Set maximum QMP command queue length to 8.  If queue full, instead of
queue the command, we directly return a "command-dropped" event, telling
client that specific command is dropped.

Note that this flow control mechanism is only valid if OOB is enabled.
If it's not, the effective queue length will always be 1, which strictly
follows original behavior of QMP command handling (which never drop
messages).

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/monitor.c b/monitor.c
index 51d12412fa..bf0f3d1662 100644
--- a/monitor.c
+++ b/monitor.c
@@ -4055,6 +4055,8 @@ static void monitor_qmp_bh_dispatcher(void *data)
     }
 }
 
+#define  QMP_REQ_QUEUE_LEN_MAX  (8)
+
 static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
 {
     QObject *req, *id = NULL;
@@ -4088,6 +4090,9 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
     req_obj->req = req;
     req_obj->need_resume = false;
 
+    /* Protect qmp_requests and fetching its length. */
+    qemu_mutex_lock(&mon->qmp.qmp_queue_lock);
+
     /*
      * If OOB is not enabled on current monitor, we'll emulate the old
      * behavior that we won't process current monitor any more until
@@ -4097,6 +4102,18 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
     if (!qmp_oob_enabled(mon)) {
         monitor_suspend(mon);
         req_obj->need_resume = true;
+    } else {
+        /* Drop the request if queue is full. */
+        if (mon->qmp.qmp_requests->length >= QMP_REQ_QUEUE_LEN_MAX) {
+            qemu_mutex_unlock(&mon->qmp.qmp_queue_lock);
+            qapi_event_send_command_dropped(id,
+                                            COMMAND_DROP_REASON_QUEUE_FULL,
+                                            NULL);
+            qobject_decref(id);
+            qobject_decref(req);
+            g_free(req_obj);
+            return;
+        }
     }
 
     /*
@@ -4104,7 +4121,6 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
      * handled in time order.  Ownership for req_obj, req, id,
      * etc. will be delivered to the handler side.
      */
-    qemu_mutex_lock(&mon->qmp.qmp_queue_lock);
     g_queue_push_tail(mon->qmp.qmp_requests, req_obj);
     qemu_mutex_unlock(&mon->qmp.qmp_queue_lock);
 
-- 
2.14.3

[Qemu-devel] [PATCH v7 17/23] qapi: introduce new cmd option "allow-oob"

[Peter Xu]

Here "oob" stands for "Out-Of-Band".  When "allow-oob" is set, it means
the command allows out-of-band execution.

The "oob" idea is proposed by Markus Armbruster in following thread:

  https://lists.gnu.org/archive/html/qemu-devel/2017-09/msg02057.html

This new "allow-oob" boolean will be exposed by "query-qmp-schema" as
well for command entries, so that QMP clients can know which command can
be used as out-of-band calls. For example the command "migrate"
originally looks like:

  {"name": "migrate", "ret-type": "17", "meta-type": "command",
   "arg-type": "86"}

And it'll be changed into:

  {"name": "migrate", "ret-type": "17", "allow-oob": false,
   "meta-type": "command", "arg-type": "86"}

This patch only provides the QMP interface level changes.  It does not
contains the real out-of-band execution implementation yet.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/qapi/qmp/dispatch.h    |  1 +
 qapi/introspect.json           |  6 +++++-
 scripts/qapi-commands.py       | 19 ++++++++++++++-----
 scripts/qapi-introspect.py     | 10 ++++++++--
 scripts/qapi.py                | 15 ++++++++++-----
 scripts/qapi2texi.py           |  2 +-
 tests/qapi-schema/test-qapi.py |  2 +-
 7 files changed, 40 insertions(+), 15 deletions(-)

diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
index 20578dcd48..b76798800c 100644
--- a/include/qapi/qmp/dispatch.h
+++ b/include/qapi/qmp/dispatch.h
@@ -23,6 +23,7 @@ typedef enum QmpCommandOptions
 {
     QCO_NO_OPTIONS = 0x0,
     QCO_NO_SUCCESS_RESP = 0x1,
+    QCO_ALLOW_OOB = 0x2,
 } QmpCommandOptions;
 
 typedef struct QmpCommand
diff --git a/qapi/introspect.json b/qapi/introspect.json
index 5b3e6e9d78..c7f67b7d78 100644
--- a/qapi/introspect.json
+++ b/qapi/introspect.json
@@ -259,12 +259,16 @@
 #
 # @ret-type: the name of the command's result type.
 #
+# @allow-oob: whether the command allows out-of-band execution.
+#             (Since: 2.12)
+#
 # TODO: @success-response (currently irrelevant, because it's QGA, not QMP)
 #
 # Since: 2.5
 ##
 { 'struct': 'SchemaInfoCommand',
-  'data': { 'arg-type': 'str', 'ret-type': 'str' } }
+  'data': { 'arg-type': 'str', 'ret-type': 'str',
+            'allow-oob': 'bool' } }
 
 ##
 # @SchemaInfoEvent:
diff --git a/scripts/qapi-commands.py b/scripts/qapi-commands.py
index 974d0a4a80..b2b0bc0510 100644
--- a/scripts/qapi-commands.py
+++ b/scripts/qapi-commands.py
@@ -192,10 +192,18 @@ out:
     return ret
 
 
-def gen_register_command(name, success_response):
-    options = 'QCO_NO_OPTIONS'
+def gen_register_command(name, success_response, allow_oob):
+    options = []
+
     if not success_response:
-        options = 'QCO_NO_SUCCESS_RESP'
+        options += ['QCO_NO_SUCCESS_RESP']
+    if allow_oob:
+        options += ['QCO_ALLOW_OOB']
+
+    if not options:
+        options = ['QCO_NO_OPTIONS']
+
+    options = " | ".join(options)
 
     ret = mcgen('''
     qmp_register_command(cmds, "%(name)s",
@@ -241,7 +249,7 @@ class QAPISchemaGenCommandVisitor(QAPISchemaVisitor):
         self._visited_ret_types = None
 
     def visit_command(self, name, info, arg_type, ret_type,
-                      gen, success_response, boxed):
+                      gen, success_response, boxed, allow_oob):
         if not gen:
             return
         self.decl += gen_command_decl(name, arg_type, boxed, ret_type)
@@ -250,7 +258,8 @@ class QAPISchemaGenCommandVisitor(QAPISchemaVisitor):
             self.defn += gen_marshal_output(ret_type)
         self.decl += gen_marshal_decl(name)
         self.defn += gen_marshal(name, arg_type, boxed, ret_type)
-        self._regy += gen_register_command(name, success_response)
+        self._regy += gen_register_command(name, success_response,
+                                           allow_oob)
 
 
 (input_file, output_dir, do_c, do_h, prefix, opts) = parse_command_line()
diff --git a/scripts/qapi-introspect.py b/scripts/qapi-introspect.py
index 032bcea491..9fbf88b644 100644
--- a/scripts/qapi-introspect.py
+++ b/scripts/qapi-introspect.py
@@ -28,6 +28,11 @@ def to_json(obj, level=0):
                               to_json(obj[key], level + 1))
                 for key in sorted(obj.keys())]
         ret = '{' + ', '.join(elts) + '}'
+    elif isinstance(obj, bool):
+        if obj:
+            ret = 'true'
+        else:
+            ret = 'false'
     else:
         assert False                # not implemented
     if level == 1:
@@ -154,12 +159,13 @@ const char %(c_name)s[] = %(c_string)s;
                                     for m in variants.variants]})
 
     def visit_command(self, name, info, arg_type, ret_type,
-                      gen, success_response, boxed):
+                      gen, success_response, boxed, allow_oob):
         arg_type = arg_type or self._schema.the_empty_object_type
         ret_type = ret_type or self._schema.the_empty_object_type
         self._gen_json(name, 'command',
                        {'arg-type': self._use_type(arg_type),
-                        'ret-type': self._use_type(ret_type)})
+                        'ret-type': self._use_type(ret_type),
+                        'allow-oob': allow_oob})
 
     def visit_event(self, name, info, arg_type, boxed):
         arg_type = arg_type or self._schema.the_empty_object_type
diff --git a/scripts/qapi.py b/scripts/qapi.py
index 43a54bf40f..61cc33660b 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -911,7 +911,8 @@ def check_exprs(exprs):
         elif 'command' in expr:
             meta = 'command'
             check_keys(expr_elem, 'command', [],
-                       ['data', 'returns', 'gen', 'success-response', 'boxed'])
+                       ['data', 'returns', 'gen', 'success-response',
+                        'boxed', 'allow-oob'])
         elif 'event' in expr:
             meta = 'event'
             check_keys(expr_elem, 'event', [], ['data', 'boxed'])
@@ -1022,7 +1023,7 @@ class QAPISchemaVisitor(object):
         pass
 
     def visit_command(self, name, info, arg_type, ret_type,
-                      gen, success_response, boxed):
+                      gen, success_response, boxed, allow_oob):
         pass
 
     def visit_event(self, name, info, arg_type, boxed):
@@ -1389,7 +1390,7 @@ class QAPISchemaAlternateType(QAPISchemaType):
 
 class QAPISchemaCommand(QAPISchemaEntity):
     def __init__(self, name, info, doc, arg_type, ret_type,
-                 gen, success_response, boxed):
+                 gen, success_response, boxed, allow_oob):
         QAPISchemaEntity.__init__(self, name, info, doc)
         assert not arg_type or isinstance(arg_type, str)
         assert not ret_type or isinstance(ret_type, str)
@@ -1400,6 +1401,7 @@ class QAPISchemaCommand(QAPISchemaEntity):
         self.gen = gen
         self.success_response = success_response
         self.boxed = boxed
+        self.allow_oob = allow_oob
 
     def check(self, schema):
         if self._arg_type_name:
@@ -1423,7 +1425,8 @@ class QAPISchemaCommand(QAPISchemaEntity):
     def visit(self, visitor):
         visitor.visit_command(self.name, self.info,
                               self.arg_type, self.ret_type,
-                              self.gen, self.success_response, self.boxed)
+                              self.gen, self.success_response,
+                              self.boxed, self.allow_oob)
 
 
 class QAPISchemaEvent(QAPISchemaEntity):
@@ -1631,6 +1634,7 @@ class QAPISchema(object):
         gen = expr.get('gen', True)
         success_response = expr.get('success-response', True)
         boxed = expr.get('boxed', False)
+        allow_oob = expr.get('allow-oob', False)
         if isinstance(data, OrderedDict):
             data = self._make_implicit_object_type(
                 name, info, doc, 'arg', self._make_members(data, info))
@@ -1638,7 +1642,8 @@ class QAPISchema(object):
             assert len(rets) == 1
             rets = self._make_array_type(rets[0], info)
         self._def_entity(QAPISchemaCommand(name, info, doc, data, rets,
-                                           gen, success_response, boxed))
+                                           gen, success_response,
+                                           boxed, allow_oob))
 
     def _def_event(self, expr, info, doc):
         name = expr['event']
diff --git a/scripts/qapi2texi.py b/scripts/qapi2texi.py
index 92e2af2cd6..634ab3edb7 100755
--- a/scripts/qapi2texi.py
+++ b/scripts/qapi2texi.py
@@ -226,7 +226,7 @@ class QAPISchemaGenDocVisitor(qapi.QAPISchemaVisitor):
                              body=texi_entity(doc, 'Members'))
 
     def visit_command(self, name, info, arg_type, ret_type,
-                      gen, success_response, boxed):
+                      gen, success_response, boxed, allow_oob):
         doc = self.cur_doc
         if boxed:
             body = texi_body(doc)
diff --git a/tests/qapi-schema/test-qapi.py b/tests/qapi-schema/test-qapi.py
index fe0ca08d78..5c3ddce6a2 100644
--- a/tests/qapi-schema/test-qapi.py
+++ b/tests/qapi-schema/test-qapi.py
@@ -36,7 +36,7 @@ class QAPISchemaTestVisitor(QAPISchemaVisitor):
         self._print_variants(variants)
 
     def visit_command(self, name, info, arg_type, ret_type,
-                      gen, success_response, boxed):
+                      gen, success_response, boxed, allow_oob):
         print 'command %s %s -> %s' % \
             (name, arg_type and arg_type.name, ret_type and ret_type.name)
         print '   gen=%s success_response=%s boxed=%s' % \
-- 
2.14.3

[Qemu-devel] [PATCH v7 18/23] qmp: support out-of-band (oob) execution

[Peter Xu]

Having "allow-oob" to true for a command does not mean that this command
will always be run in out-of-band mode.  The out-of-band quick path will
only be executed if we specify the extra "run-oob" flag when sending the
QMP request:

    { "execute":   "command-that-allows-oob",
      "arguments": { ... },
      "control":   { "run-oob": true } }

The "control" key is introduced to store this extra flag.  "control"
field is used to store arguments that are shared by all the commands,
rather than command specific arguments.  Let "run-oob" be the first.

Note that in the patch I exported qmp_dispatch_check_obj() to be used to
check the request earlier, and at the same time allowed "id" field to be
there since actually we always allow that.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/qapi/qmp/dispatch.h |  2 ++
 monitor.c                   | 84 ++++++++++++++++++++++++++++++++++++++++-----
 qapi/qmp-dispatch.c         | 32 ++++++++++++++++-
 trace-events                |  2 ++
 4 files changed, 110 insertions(+), 10 deletions(-)

diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
index b76798800c..d8d913b338 100644
--- a/include/qapi/qmp/dispatch.h
+++ b/include/qapi/qmp/dispatch.h
@@ -49,6 +49,8 @@ bool qmp_command_is_enabled(const QmpCommand *cmd);
 const char *qmp_command_name(const QmpCommand *cmd);
 bool qmp_has_success_response(const QmpCommand *cmd);
 QObject *qmp_build_error_object(Error *err);
+QDict *qmp_dispatch_check_obj(const QObject *request, Error **errp);
+bool qmp_is_oob(QDict *dict);
 
 typedef void (*qmp_cmd_callback_fn)(QmpCommand *cmd, void *opaque);
 
diff --git a/monitor.c b/monitor.c
index bf0f3d1662..d31da3fd1b 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1106,6 +1106,44 @@ static void qmp_caps_apply(Monitor *mon, QMPCapabilityList *list)
     }
 }
 
+/*
+ * Return true if check successful, or false otherwise.  When false is
+ * returned, detailed error will be in errp if provided.
+ */
+static bool qmp_cmd_oob_check(Monitor *mon, QDict *req, Error **errp)
+{
+    const char *command;
+    QmpCommand *cmd;
+
+    command = qdict_get_try_str(req, "execute");
+    if (!command) {
+        error_setg(errp, "Command field 'execute' missing");
+        return false;
+    }
+
+    cmd = qmp_find_command(mon->qmp.commands, command);
+    if (!cmd) {
+        error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
+                  "The command %s has not been found", command);
+        return false;
+    }
+
+    if (qmp_is_oob(req)) {
+        if (!qmp_oob_enabled(mon)) {
+            error_setg(errp, "Please enable Out-Of-Band first "
+                       "for the session during capabilities negociation");
+            return false;
+        }
+        if (!(cmd->options & QCO_ALLOW_OOB)) {
+            error_setg(errp, "The command %s does not support OOB",
+                       command);
+            return false;
+        }
+    }
+
+    return true;
+}
+
 void qmp_qmp_capabilities(bool has_enable, QMPCapabilityList *enable,
                           Error **errp)
 {
@@ -4049,6 +4087,7 @@ static void monitor_qmp_bh_dispatcher(void *data)
     QMPRequest *req_obj = monitor_qmp_requests_pop_one();
 
     if (req_obj) {
+        trace_monitor_qmp_cmd_in_band(qobject_get_try_str(req_obj->id) ?: "");
         monitor_qmp_dispatch_one(req_obj);
         /* Reschedule instead of looping so the main loop stays responsive */
         qemu_bh_schedule(mon_global.qmp_dispatcher_bh);
@@ -4072,17 +4111,31 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
         error_setg(&err, QERR_JSON_PARSING);
     }
     if (err) {
-        monitor_qmp_respond(mon, NULL, err, NULL);
-        qobject_decref(req);
-        return;
+        goto err;
+    }
+
+    /* Check against the request in general layout */
+    qdict = qmp_dispatch_check_obj(req, &err);
+    if (!qdict) {
+        goto err;
     }
 
-    qdict = qobject_to_qdict(req);
-    if (qdict) {
-        id = qdict_get(qdict, "id");
-        qobject_incref(id);
-        qdict_del(qdict, "id");
-    } /* else will fail qmp_dispatch() */
+    /* Check against OOB specific */
+    if (!qmp_cmd_oob_check(mon, qdict, &err)) {
+        goto err;
+    }
+
+    id = qdict_get(qdict, "id");
+
+    /* When OOB is enabled, the "id" field is mandatory. */
+    if (qmp_oob_enabled(mon) && !id) {
+        error_setg(&err, "Out-Of-Band capability requires that "
+                   "every command contains an 'id' field");
+        goto err;
+    }
+
+    qobject_incref(id);
+    qdict_del(qdict, "id");
 
     req_obj = g_new0(QMPRequest, 1);
     req_obj->mon = mon;
@@ -4090,6 +4143,14 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
     req_obj->req = req;
     req_obj->need_resume = false;
 
+    if (qmp_is_oob(qdict)) {
+        /* Out-Of-Band (OOB) requests are executed directly in parser. */
+        trace_monitor_qmp_cmd_out_of_band(qobject_get_try_str(req_obj->id)
+                                          ?: "");
+        monitor_qmp_dispatch_one(req_obj);
+        return;
+    }
+
     /* Protect qmp_requests and fetching its length. */
     qemu_mutex_lock(&mon->qmp.qmp_queue_lock);
 
@@ -4126,6 +4187,11 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
 
     /* Kick the dispatcher routine */
     qemu_bh_schedule(mon_global.qmp_dispatcher_bh);
+    return;
+
+err:
+    monitor_qmp_respond(mon, NULL, err, NULL);
+    qobject_decref(req);
 }
 
 static void monitor_qmp_read(void *opaque, const uint8_t *buf, int size)
diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
index b41fa174fe..675223e0ec 100644
--- a/qapi/qmp-dispatch.c
+++ b/qapi/qmp-dispatch.c
@@ -20,7 +20,7 @@
 #include "qapi-types.h"
 #include "qapi/qmp/qerror.h"
 
-static QDict *qmp_dispatch_check_obj(const QObject *request, Error **errp)
+QDict *qmp_dispatch_check_obj(const QObject *request, Error **errp)
 {
     const QDictEntry *ent;
     const char *arg_name;
@@ -52,6 +52,14 @@ static QDict *qmp_dispatch_check_obj(const QObject *request, Error **errp)
                            "QMP input member 'arguments' must be an object");
                 return NULL;
             }
+        } else if (!strcmp(arg_name, "id")) {
+            continue;
+        } else if (!strcmp(arg_name, "control")) {
+            if (qobject_type(arg_obj) != QTYPE_QDICT) {
+                error_setg(errp,
+                           "QMP input member 'control' must be a dict");
+                return NULL;
+            }
         } else {
             error_setg(errp, "QMP input member '%s' is unexpected",
                        arg_name);
@@ -122,6 +130,28 @@ QObject *qmp_build_error_object(Error *err)
                               error_get_pretty(err));
 }
 
+/*
+ * Detect whether a request should be run out-of-band, by quickly
+ * peeking at whether we have: { "control": { "run-oob": True } }. By
+ * default commands are run in-band.
+ */
+bool qmp_is_oob(QDict *dict)
+{
+    QBool *bool_obj;
+
+    dict = qdict_get_qdict(dict, "control");
+    if (!dict) {
+        return false;
+    }
+
+    bool_obj = qobject_to_qbool(qdict_get(dict, "run-oob"));
+    if (!bool_obj) {
+        return false;
+    }
+
+    return qbool_get_bool(bool_obj);
+}
+
 QObject *qmp_dispatch(QmpCommandList *cmds, QObject *request)
 {
     Error *err = NULL;
diff --git a/trace-events b/trace-events
index eecb68b1d5..d62d4e87ed 100644
--- a/trace-events
+++ b/trace-events
@@ -48,6 +48,8 @@ monitor_protocol_event_queue(uint32_t event, void *qdict, uint64_t rate) "event=
 handle_hmp_command(void *mon, const char *cmdline) "mon %p cmdline: %s"
 handle_qmp_command(void *mon, const char *req) "mon %p req: %s"
 monitor_suspend(void *ptr, int cnt) "mon %p: %d"
+monitor_qmp_cmd_in_band(const char *id) "%s"
+monitor_qmp_cmd_out_of_band(const char *id) "%s"
 
 # dma-helpers.c
 dma_blk_io(void *dbs, void *bs, int64_t offset, bool to_dev) "dbs=%p bs=%p offset=%" PRId64 " to_dev=%d"
-- 
2.14.3

[Qemu-devel] [PATCH v7 19/23] qmp: isolate responses into io thread

[Peter Xu]

For those monitors who have enabled IO thread, we'll offload the
responding procedure into IO thread.  The main reason is that chardev is
not thread safe, and we need to do all the read/write IOs in the same
thread.  For use_io_thr=true monitors, that thread is the IO thread.

We do this isolation in similar pattern as what we have done to the
request queue: we first create one response queue for each monitor, then
instead of replying directly in the main thread, we queue the responses
and kick the IO thread to do the rest of the job for us.

A funny thing after doing this is that, when the QMP clients send "quit"
to QEMU, it's possible that we close the IOThread even earlier than
replying to that "quit".  So another thing we need to do before cleaning
up the monitors is that we need to flush the response queue (we don't
need to do that for command queue; after all we are quitting) to make
sure replies for handled commands are always flushed back to clients.

Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 95 insertions(+), 1 deletion(-)

diff --git a/monitor.c b/monitor.c
index d31da3fd1b..eac92c9b86 100644
--- a/monitor.c
+++ b/monitor.c
@@ -175,6 +175,8 @@ typedef struct {
     QemuMutex qmp_queue_lock;
     /* Input queue that holds all the parsed QMP requests */
     GQueue *qmp_requests;
+    /* Output queue contains all the QMP responses in order */
+    GQueue *qmp_responses;
 } MonitorQMP;
 
 /*
@@ -201,6 +203,7 @@ struct Monitor {
     bool skip_flush;
     bool use_io_thr;
 
+    /* We can't access guest memory when holding the lock */
     QemuMutex out_lock;
     QString *outbuf;
     guint out_watch;
@@ -223,6 +226,8 @@ static struct {
     IOThread *mon_iothread;
     /* Bottom half to dispatch the requests received from IO thread */
     QEMUBH *qmp_dispatcher_bh;
+    /* Bottom half to deliver the responses back to clients */
+    QEMUBH *qmp_respond_bh;
 } mon_global;
 
 /* QMP checker flags */
@@ -412,7 +417,8 @@ int monitor_fprintf(FILE *stream, const char *fmt, ...)
     return 0;
 }
 
-static void monitor_json_emitter(Monitor *mon, const QObject *data)
+static void monitor_json_emitter_raw(Monitor *mon,
+                                     QObject *data)
 {
     QString *json;
 
@@ -426,6 +432,71 @@ static void monitor_json_emitter(Monitor *mon, const QObject *data)
     QDECREF(json);
 }
 
+static void monitor_json_emitter(Monitor *mon, QObject *data)
+{
+    if (mon->use_io_thr) {
+        /*
+         * If using IO thread, we need to queue the item so that IO
+         * thread will do the rest for us.  Take refcount so that
+         * caller won't free the data (which will be finally freed in
+         * responder thread).
+         */
+        qobject_incref(data);
+        qemu_mutex_lock(&mon->qmp.qmp_queue_lock);
+        g_queue_push_tail(mon->qmp.qmp_responses, (void *)data);
+        qemu_mutex_unlock(&mon->qmp.qmp_queue_lock);
+        qemu_bh_schedule(mon_global.qmp_respond_bh);
+    } else {
+        /*
+         * If not using monitor IO thread, then we are in main thread.
+         * Do the emission right away.
+         */
+        monitor_json_emitter_raw(mon, data);
+    }
+}
+
+struct QMPResponse {
+    Monitor *mon;
+    QObject *data;
+};
+typedef struct QMPResponse QMPResponse;
+
+/*
+ * Return one QMPResponse.  The response is only valid if
+ * response.data is not NULL.
+ */
+static QMPResponse monitor_qmp_response_pop_one(void)
+{
+    Monitor *mon;
+    QObject *data = NULL;
+
+    qemu_mutex_lock(&monitor_lock);
+    QTAILQ_FOREACH(mon, &mon_list, entry) {
+        qemu_mutex_lock(&mon->qmp.qmp_queue_lock);
+        data = g_queue_pop_head(mon->qmp.qmp_responses);
+        qemu_mutex_unlock(&mon->qmp.qmp_queue_lock);
+        if (data) {
+            break;
+        }
+    }
+    qemu_mutex_unlock(&monitor_lock);
+    return (QMPResponse) { .mon = mon, .data = data };
+}
+
+static void monitor_qmp_bh_responder(void *opaque)
+{
+    QMPResponse response;
+
+    while (true) {
+        response = monitor_qmp_response_pop_one();
+        if (!response.data) {
+            break;
+        }
+        monitor_json_emitter_raw(response.mon, response.data);
+        qobject_decref(response.data);
+    }
+}
+
 static MonitorQAPIEventConf monitor_qapi_event_conf[QAPI_EVENT__MAX] = {
     /* Limit guest-triggerable events to 1 per second */
     [QAPI_EVENT_RTC_CHANGE]        = { 1000 * SCALE_MS },
@@ -612,6 +683,7 @@ static void monitor_data_init(Monitor *mon, bool skip_flush,
     mon->skip_flush = skip_flush;
     mon->use_io_thr = use_io_thr;
     mon->qmp.qmp_requests = g_queue_new();
+    mon->qmp.qmp_responses = g_queue_new();
 }
 
 static void monitor_data_destroy(Monitor *mon)
@@ -626,6 +698,7 @@ static void monitor_data_destroy(Monitor *mon)
     qemu_mutex_destroy(&mon->out_lock);
     qemu_mutex_destroy(&mon->qmp.qmp_queue_lock);
     g_queue_free(mon->qmp.qmp_requests);
+    g_queue_free(mon->qmp.qmp_responses);
 }
 
 char *qmp_human_monitor_command(const char *command_line, bool has_cpu_index,
@@ -4413,6 +4486,15 @@ static void monitor_iothread_init(void)
     mon_global.qmp_dispatcher_bh = aio_bh_new(qemu_get_aio_context(),
                                               monitor_qmp_bh_dispatcher,
                                               NULL);
+
+    /*
+     * Unlike the dispatcher BH, this must be run on the monitor IO
+     * thread, so that monitors that are using IO thread will make
+     * sure read/write operations are all done on the IO thread.
+     */
+    mon_global.qmp_respond_bh = aio_bh_new(monitor_aio_context_get(),
+                                           monitor_qmp_bh_responder,
+                                           NULL);
 }
 
 void monitor_init_globals(void)
@@ -4560,9 +4642,19 @@ void monitor_cleanup(void)
      */
     iothread_stop(mon_global.mon_iothread);
 
+    /*
+     * After we have IOThread to send responses, it's possible that
+     * when we stop the IOThread there are still replies queued in the
+     * responder queue.  Flush all of them.  Note that even after this
+     * flush it's still possible that out buffer is not flushed.
+     * It'll be done in below monitor_flush() as the last resort.
+     */
+    monitor_qmp_bh_responder(NULL);
+
     qemu_mutex_lock(&monitor_lock);
     QTAILQ_FOREACH_SAFE(mon, &mon_list, entry, next) {
         QTAILQ_REMOVE(&mon_list, mon, entry);
+        monitor_flush(mon);
         monitor_data_destroy(mon);
         g_free(mon);
     }
@@ -4571,6 +4663,8 @@ void monitor_cleanup(void)
     /* QEMUBHs needs to be deleted before destroying the IOThread. */
     qemu_bh_delete(mon_global.qmp_dispatcher_bh);
     mon_global.qmp_dispatcher_bh = NULL;
+    qemu_bh_delete(mon_global.qmp_respond_bh);
+    mon_global.qmp_respond_bh = NULL;
 
     iothread_destroy(mon_global.mon_iothread);
     mon_global.mon_iothread = NULL;
-- 
2.14.3

[Qemu-devel] [PATCH v7 20/23] monitor: enable IO thread for (qmp & !mux) typed

[Peter Xu]

Start to use dedicate IO thread for QMP monitors that are not using
MUXed chardev.

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/monitor.c b/monitor.c
index eac92c9b86..5b7da2b574 100644
--- a/monitor.c
+++ b/monitor.c
@@ -36,6 +36,7 @@
 #include "net/slirp.h"
 #include "chardev/char-fe.h"
 #include "chardev/char-io.h"
+#include "chardev/char-mux.h"
 #include "ui/qemu-spice.h"
 #include "sysemu/numa.h"
 #include "monitor/monitor.h"
@@ -4579,8 +4580,10 @@ static void monitor_qmp_setup_handlers(void *data)
 void monitor_init(Chardev *chr, int flags)
 {
     Monitor *mon = g_malloc(sizeof(*mon));
+    /* Enable IOThread for QMPs that are not using MUX chardev backends. */
+    bool use_io_thr = (!CHARDEV_IS_MUX(chr)) && (flags & MONITOR_USE_CONTROL);
 
-    monitor_data_init(mon, false, false);
+    monitor_data_init(mon, false, use_io_thr);
 
     qemu_chr_fe_init(&mon->chr, chr, &error_abort);
     mon->flags = flags;
-- 
2.14.3

[Qemu-devel] [PATCH v7 21/23] qmp: add command "x-oob-test"

[Peter Xu]

This command is only used to test OOB functionality.  It should not be
used for any other purposes.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 qapi-schema.json | 18 ++++++++++++++++++
 qmp.c            | 16 ++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/qapi-schema.json b/qapi-schema.json
index d6c89efc0d..59ea3e2051 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3252,3 +3252,21 @@
 ##
 { 'event': 'COMMAND_DROPPED' ,
   'data': { 'id': 'any', 'reason': 'CommandDropReason' } }
+
+##
+# @x-oob-test:
+#
+# Test OOB functionality.  When send this command with lock=true,
+# it'll try to hang the dispatcher.  When send it with lock=false,
+# it'll try to notify the locked thread to continue.  Note: it should
+# only be used by QMP test program rather than anything else.
+#
+# Since: 2.12
+#
+# Example:
+#
+# { "execute": "x-oob-test",
+#   "arguments": { "lock": true } }
+##
+{ 'command': 'x-oob-test', 'data' : { 'lock': 'bool' },
+  'allow-oob': true }
diff --git a/qmp.c b/qmp.c
index 52cfd2d81c..c7dcbe72e3 100644
--- a/qmp.c
+++ b/qmp.c
@@ -717,3 +717,19 @@ MemoryInfo *qmp_query_memory_size_summary(Error **errp)
 
     return mem_info;
 }
+
+static QemuSemaphore x_oob_test_sem;
+
+static void __attribute__((constructor)) x_oob_test_init(void)
+{
+    qemu_sem_init(&x_oob_test_sem, 0);
+}
+
+void qmp_x_oob_test(bool lock, Error **errp)
+{
+    if (lock) {
+        qemu_sem_wait(&x_oob_test_sem);
+    } else {
+        qemu_sem_post(&x_oob_test_sem);
+    }
+}
-- 
2.14.3

[Qemu-devel] [PATCH v7 22/23] tests: qmp-test: verify command batching

[Peter Xu]

OOB introduced DROP event for flow control.  This should not affect old
QMP clients.  Add a command batching check to make sure of it.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 tests/qmp-test.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/tests/qmp-test.c b/tests/qmp-test.c
index 11b384c829..19fa774486 100644
--- a/tests/qmp-test.c
+++ b/tests/qmp-test.c
@@ -78,6 +78,7 @@ static void test_qmp_protocol(void)
     QList *capabilities;
     const QListEntry *entry;
     QString *qstr;
+    int i;
 
     global_qtest = qtest_init_without_qmp_handshake(common_args);
 
@@ -135,6 +136,27 @@ static void test_qmp_protocol(void)
     g_assert_cmpint(qdict_get_int(resp, "id"), ==, 2);
     QDECREF(resp);
 
+    /*
+     * Test command batching.  In current test OOB is not enabled, we
+     * should be able to run as many commands in batch as we like.
+     * Using 16 (>8, which is OOB queue length) to make sure OOB won't
+     * break existing clients.  Note: this test does not control the
+     * scheduling of QEMU's QMP command processing threads so it may
+     * not really trigger batching inside QEMU.  This is just a
+     * best-effort test.
+     */
+    for (i = 0; i < 16; i++) {
+        qmp_async("{ 'execute': 'query-version' }");
+    }
+    /* Verify the replies to make sure no command is dropped. */
+    for (i = 0; i < 16; i++) {
+        resp = qmp_receive();
+        /* It should never be dropped.  Each of them should be a reply. */
+        g_assert(qdict_haskey(resp, "return"));
+        g_assert(!qdict_haskey(resp, "event"));
+        QDECREF(resp);
+    }
+
     qtest_end();
 }
 
-- 
2.14.3

[Qemu-devel] [PATCH v7 23/23] tests: qmp-test: add oob test

[Peter Xu]

Test the new OOB capability.  Here we used the new "x-oob-test" command.
Firstly, we send a lock=true and oob=false command to hang the main
thread.  Then send another lock=false and oob=true command (which will
be run inside parser this time) to free that hanged command.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 tests/qmp-test.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/tests/qmp-test.c b/tests/qmp-test.c
index 19fa774486..c41e8305b6 100644
--- a/tests/qmp-test.c
+++ b/tests/qmp-test.c
@@ -160,6 +160,70 @@ static void test_qmp_protocol(void)
     qtest_end();
 }
 
+/* Tests for Out-Of-Band support. */
+static void test_qmp_oob(void)
+{
+    QDict *resp;
+    int acks = 0;
+    const char *cmd_id;
+
+    global_qtest = qtest_init_without_qmp_handshake(common_args);
+
+    /* Ignore the greeting message. */
+    resp = qmp_receive();
+    g_assert(qdict_get_qdict(resp, "QMP"));
+    QDECREF(resp);
+
+    /* Try a fake capability, it should fail. */
+    resp = qmp("{ 'execute': 'qmp_capabilities', "
+               "  'arguments': { 'enable': [ 'cap-does-not-exist' ] } }");
+    g_assert(qdict_haskey(resp, "error"));
+    QDECREF(resp);
+
+    /* Now, enable OOB in current QMP session, it should success. */
+    resp = qmp("{ 'execute': 'qmp_capabilities', "
+               "  'arguments': { 'enable': [ 'oob' ] } }");
+    g_assert(qdict_haskey(resp, "return"));
+    QDECREF(resp);
+
+    /*
+     * Try any command that does not support OOB but with OOB flag. We
+     * should get failure.
+     */
+    resp = qmp("{ 'execute': 'query-cpus',"
+               "  'control': { 'run-oob': true } }");
+    g_assert(qdict_haskey(resp, "error"));
+    QDECREF(resp);
+
+    /*
+     * Firstly send the "x-oob-test" command with lock=true and
+     * oob=false, it should hang the dispatcher and main thread;
+     * later, we send another lock=false with oob=true to continue
+     * that thread processing.  Finally we should receive replies from
+     * both commands.
+     */
+    qmp_async("{ 'execute': 'x-oob-test',"
+              "  'arguments': { 'lock': true }, "
+              "  'id': 'lock-cmd'}");
+    qmp_async("{ 'execute': 'x-oob-test', "
+              "  'arguments': { 'lock': false }, "
+              "  'control': { 'run-oob': true }, "
+              "  'id': 'unlock-cmd' }");
+
+    /* Ignore all events.  Wait for 2 acks */
+    while (acks < 2) {
+        resp = qmp_receive();
+        cmd_id = qdict_get_str(resp, "id");
+        if (!g_strcmp0(cmd_id, "lock-cmd") ||
+            !g_strcmp0(cmd_id, "unlock-cmd")) {
+            acks++;
+        }
+        QDECREF(resp);
+    }
+
+    qtest_end();
+}
+
 static int query_error_class(const char *cmd)
 {
     static struct {
@@ -339,6 +403,7 @@ int main(int argc, char *argv[])
     g_test_init(&argc, &argv, NULL);
 
     qtest_add_func("qmp/protocol", test_qmp_protocol);
+    qtest_add_func("qmp/oob", test_qmp_oob);
     qmp_schema_init(&schema);
     add_query_tests(&schema);
 
-- 
2.14.3

Re: [Qemu-devel] [PATCH v7 00/23] QMP: out-of-band (OOB) execution support

[Peter Xu]

On Wed, Jan 24, 2018 at 01:39:34PM +0800, Peter Xu wrote:
> This version should have addressed all comments in previous one, also
> fixed another race condition after I addressed all the comments (a new
> race condition introduced by addressing the comments...).  For some
> more details of the race condition, please see the last entry of
> change log, and please refer to patch 9 for the code change.
> 
> I removed RFC tag from this version.  Please review.  Thanks.
> 
> v7:
> - add some r-bs, and remove some.
> - remove the chardev fix since already queued by Paolo
> - use local var in qemu_chr_fe_add_watch [Stefan]
> - move doc patch to front, mention it in some patches [Eric]
> - Quite a few of English fixes [Eric]
> - fix unlock missing in handle_qmp_command [Stefan]
> - squash some patches according to the review comments
> - don't break gdbserver usage on HMP non-interactive mode by fixing up
>   the suspend/resume logic [Fam, Stefan]
> - move the qemu_chr_fe_set_handlers() call in monitor_init() into a
>   bottom half to avoid race between the call itself and
>   iothread. [Stefan]
> - spent quite a lot of time debugging another assertion failure in
>   io_watch_poll_finalize() after above change is made (ouch! I really
>   hoped we always have the latest glib): when QEMU inits chardevs in
>   chardev_init_func() it's possible that QEMU registers the chardev
>   handlers there, even before CharBackend is connected to that chardev
>   in monitor_init().  Then, when we reach monitor_init() we must make
>   sure we unregister that old one first, or there can have one orphan
>   GSource still in default gcontext (note that this can really happen
>   when we start to use QEMUBH to setup chardev frontends, which is
>   above change).

Online repository updated for v7:

  https://github.com/xzpeter/qemu/tree/monitor-oob

Thanks,

-- 
Peter Xu

Re: [Qemu-devel] [PATCH v7 00/23] QMP: out-of-band (OOB) execution support

[Dr. David Alan Gilbert]

* Peter Xu (peterx@redhat.com) wrote:
> On Wed, Jan 24, 2018 at 01:39:34PM +0800, Peter Xu wrote:
> > This version should have addressed all comments in previous one, also
> > fixed another race condition after I addressed all the comments (a new
> > race condition introduced by addressing the comments...).  For some
> > more details of the race condition, please see the last entry of
> > change log, and please refer to patch 9 for the code change.
> > 
> > I removed RFC tag from this version.  Please review.  Thanks.
> > 
> > v7:
> > - add some r-bs, and remove some.
> > - remove the chardev fix since already queued by Paolo
> > - use local var in qemu_chr_fe_add_watch [Stefan]
> > - move doc patch to front, mention it in some patches [Eric]
> > - Quite a few of English fixes [Eric]
> > - fix unlock missing in handle_qmp_command [Stefan]
> > - squash some patches according to the review comments
> > - don't break gdbserver usage on HMP non-interactive mode by fixing up
> >   the suspend/resume logic [Fam, Stefan]
> > - move the qemu_chr_fe_set_handlers() call in monitor_init() into a
> >   bottom half to avoid race between the call itself and
> >   iothread. [Stefan]
> > - spent quite a lot of time debugging another assertion failure in
> >   io_watch_poll_finalize() after above change is made (ouch! I really
> >   hoped we always have the latest glib): when QEMU inits chardevs in
> >   chardev_init_func() it's possible that QEMU registers the chardev
> >   handlers there, even before CharBackend is connected to that chardev
> >   in monitor_init().  Then, when we reach monitor_init() we must make
> >   sure we unregister that old one first, or there can have one orphan
> >   GSource still in default gcontext (note that this can really happen
> >   when we start to use QEMUBH to setup chardev frontends, which is
> >   above change).
> 
> Online repository updated for v7:
> 
>   https://github.com/xzpeter/qemu/tree/monitor-oob

This version seems to have fixed the problem I had where after an error
I couldn't reconnect (the one I mentioned on the 12th).

Dave

> Thanks,
> 
> -- 
> Peter Xu
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH v7 00/23] QMP: out-of-band (OOB) execution support

[Peter Xu]

On Wed, Jan 24, 2018 at 01:39:34PM +0800, Peter Xu wrote:
> This version should have addressed all comments in previous one, also
> fixed another race condition after I addressed all the comments (a new
> race condition introduced by addressing the comments...).  For some
> more details of the race condition, please see the last entry of
> change log, and please refer to patch 9 for the code change.
> 
> I removed RFC tag from this version.  Please review.  Thanks.

It's still a month there until the soft freeze of 2.12, but I would
still like to have a gentle ping for this series in case there will be
further surprises.  Hopefully, this series can catch the train for 2.12.

I'll respin the postcopy recovery series very soon.  Thanks,

-- 
Peter Xu

Re: [Qemu-devel] [PATCH v7 01/23] docs: update QMP documents for OOB commands

[Eric Blake]

On 01/23/2018 11:39 PM, Peter Xu wrote:
> Update both the developer and spec for the new QMP OOB (Out-Of-Band)
> command.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>   docs/devel/qapi-code-gen.txt | 68 ++++++++++++++++++++++++++++++++++++++++----
>   docs/interop/qmp-spec.txt    | 30 ++++++++++++++++---
>   2 files changed, 89 insertions(+), 9 deletions(-)
> 
> diff --git a/docs/devel/qapi-code-gen.txt b/docs/devel/qapi-code-gen.txt
> index 06ab699066..4d3db0ad39 100644
> --- a/docs/devel/qapi-code-gen.txt
> +++ b/docs/devel/qapi-code-gen.txt
> @@ -554,9 +554,12 @@ following example objects:
>   
>   === Commands ===
>   
> +--- General Command Layout ---
> +
>   Usage: { 'command': STRING, '*data': COMPLEX-TYPE-NAME-OR-DICT,
>            '*returns': TYPE-NAME, '*boxed': true,
> -         '*gen': false, '*success-response': false }
> +         '*gen': false, '*success-response': false,
> +         '*allow-oob': false }
>   

Shouldn't this be '*allow-oob': true, as the only time you add the field 
is if you turn oob on (as it already defaults to off)?

>   Commands are defined by using a dictionary containing several members,
>   where three members are most common.  The 'command' member is a
> @@ -636,6 +639,59 @@ possible, the command expression should include the optional key
>   'success-response' with boolean value false.  So far, only QGA makes
>   use of this member.
>   
> +A command can be declared to support Out-Of-Band (OOB) execution.  By
> +default, commands do not support OOB.  To declare a command to support

s/to support/that supports/

> +it, we need an extra 'allow-oob' field.  For example:
> +
> + { 'command': 'migrate_recover',
> +   'data': { 'uri': 'str' }, 'allow-oob': true }
> +
> +To execute a command in Out-Of-Band way, we need to specify the
> +"control" field in the request, with "run-oob" set to true. Example:
> +
> + => { "execute": "command-support-oob",
> +      "arguments": { ... },
> +      "control": { "run-oob": true } }
> + <= { "return": { } }

This talks more about the QMP user protocol, while the rest of the 
document is about QAPI constructs.  But we do have an example of 
'my-first-command' in the document, so I guess this is okay.

> +
> +Without it, even the commands that support out-of-band execution will
> +still be run In-Band.
> +
> +Please read the "Out-Of-Band Command Execution" section below for more
> +information on how OOB execution works.
> +
> +--- About Out-Of-Band (OOB) Command Execution ---

Do we really need the paragraph mentioning a forward reference, when the 
very next thing is the item that was referenced?

> +
> +Out-Of-Band does not mean a special kind of command. Instead, it's a
> +special way to execute the command.  One normal command can be
> +declared to support Out-Of-Band execution when 'allow-oob' field is
> +set to true when defining the command.  With that, it can be run in an
> +Out-Of-Band way if 'run-oob' is specified in 'control' field of
> +command request.
> +
> +When we say normal QMP command executions, it means basically the
> +following:


Under normal QMP command execution, the following apply to each command:

> +
> +- They are executed in order,
> +- They run only in main thread of QEMU,
> +- They have the BQL taken during execution.
> +
> +For OOB command executions, they differ in the following:

When a command is executed with OOB, the following changes occur:

> +
> +- They can be executed before an existing command,

They can be completed before a pending in-band command,

> +- They run in a monitor dedicated thread,
> +- They do not take the BQL during execution.
> +
> +OOB command handlers must satisfy the following conditions:
> +
> +- It executes extremely fast,
> +- It does not take any lock, or, it can take very small locks if all
> +  critical regions also follow the rules for OOB command handler code,
> +- It does not invoke system calls that may block,
> +- It does not access guest RAM that may block when userfaultfd is
> +  enabled for postcopy live migration.
> +
> +If in doubt, do not implement OOB execution support.
>   
>   === Events ===
>   
> @@ -739,10 +795,12 @@ references by name.
>   QAPI schema definitions not reachable that way are omitted.
>   
>   The SchemaInfo for a command has meta-type "command", and variant
> -members "arg-type" and "ret-type".  On the wire, the "arguments"
> -member of a client's "execute" command must conform to the object type
> -named by "arg-type".  The "return" member that the server passes in a
> -success response conforms to the type named by "ret-type".
> +members "arg-type", "ret-type" and "allow-oob".  On the wire, the
> +"arguments" member of a client's "execute" command must conform to the
> +object type named by "arg-type".  The "return" member that the server
> +passes in a success response conforms to the type named by
> +"ret-type".  When "allow-oob" is set, it means the command supports
> +out-of-band execution.
>   
>   If the command takes no arguments, "arg-type" names an object type
>   without members.  Likewise, if the command returns nothing, "ret-type"
> diff --git a/docs/interop/qmp-spec.txt b/docs/interop/qmp-spec.txt
> index f8b5356015..e20163c138 100644
> --- a/docs/interop/qmp-spec.txt
> +++ b/docs/interop/qmp-spec.txt
> @@ -83,16 +83,27 @@ The greeting message format is:
>   2.2.1 Capabilities
>   ------------------
>   
> -As of the date this document was last revised, no server or client
> -capability strings have been defined.
> +Currently supported capabilities are:
>   
> +- "oob": it means the QMP server supports "Out-Of-Band" command
> +  execution.  For more detail, please see "run-oob" parameter in

s/detail/details/

> +  "Issuing Commands" section below.  Not all commands allow this "oob"
> +  execution.  One can know whether one command supports "oob" by
> +  "query-qmp-schema" command.

The "query-qmp-schema" command can be used to inspect which commands 
support "oob" execution.

> +
> +QMP clients can get a list of supported QMP capabilities of the QMP
> +server in the greeting message mentioned above.  By default, all the
> +capabilities are off.  To enable a specific or multiple of QMP

s/specific or multiple of/any/

> +capabilities, QMP client needs to send "qmp_capabilities" command with

s/QMP/the QMP
s/send/send the/
s/with/with an/

> +extra parameter for the capabilities.

s/the/the requested/

>   
>   2.3 Issuing Commands
>   --------------------
>   
>   The format for command execution is:
>   
> -{ "execute": json-string, "arguments": json-object, "id": json-value }
> +{ "execute": json-string, "arguments": json-object, "id": json-value,
> +  "control": json-dict }
>   
>    Where,
>   
> @@ -102,10 +113,16 @@ The format for command execution is:
>     required. Each command documents what contents will be considered
>     valid when handling the json-argument
>   - The "id" member is a transaction identification associated with the
> -  command execution, it is optional and will be part of the response if
> +  command execution.  It is required if OOB is enabled, and optional
> +  if not.  The same "id" field will be part of the response if
>     provided. The "id" member can be any json-value, although most
>     clients merely use a json-number incremented for each successive
>     command
> +- The "control" member is optional, and currently only used for
> +  "out-of-band" execution ("oob" as shortcut). The handling or
> +  response of an "oob" command can overtake prior in-band commands.
> +  To enable "oob" feature, just provide a control field with: {

To enable "oob" handling of a particular command,

> +  "control": { "run-oob": true } }
>   
>   2.4 Commands Responses
>   ----------------------
> @@ -113,6 +130,11 @@ The format for command execution is:
>   There are two possible responses which the Server will issue as the result
>   of a command execution: success or error.
>   
> +As long as the commands were issued with a proper "id" field, then the
> +same "id" field will be attached in the corresponding response message
> +so that requests and responses can match.  Clients should drop all the
> +responses that are with unknown "id" field.
> +
>   2.4.1 success
>   -------------
>   
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Re: [Qemu-devel] [PATCH v7 01/23] docs: update QMP documents for OOB commands

[Peter Xu]

On Fri, Feb 09, 2018 at 08:10:53AM -0600, Eric Blake wrote:
> On 01/23/2018 11:39 PM, Peter Xu wrote:
> > Update both the developer and spec for the new QMP OOB (Out-Of-Band)
> > command.
> > 
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> >   docs/devel/qapi-code-gen.txt | 68 ++++++++++++++++++++++++++++++++++++++++----
> >   docs/interop/qmp-spec.txt    | 30 ++++++++++++++++---
> >   2 files changed, 89 insertions(+), 9 deletions(-)
> > 
> > diff --git a/docs/devel/qapi-code-gen.txt b/docs/devel/qapi-code-gen.txt
> > index 06ab699066..4d3db0ad39 100644
> > --- a/docs/devel/qapi-code-gen.txt
> > +++ b/docs/devel/qapi-code-gen.txt
> > @@ -554,9 +554,12 @@ following example objects:
> >   === Commands ===
> > +--- General Command Layout ---
> > +
> >   Usage: { 'command': STRING, '*data': COMPLEX-TYPE-NAME-OR-DICT,
> >            '*returns': TYPE-NAME, '*boxed': true,
> > -         '*gen': false, '*success-response': false }
> > +         '*gen': false, '*success-response': false,
> > +         '*allow-oob': false }
> 
> Shouldn't this be '*allow-oob': true, as the only time you add the field is
> if you turn oob on (as it already defaults to off)?
> 
> >   Commands are defined by using a dictionary containing several members,
> >   where three members are most common.  The 'command' member is a
> > @@ -636,6 +639,59 @@ possible, the command expression should include the optional key
> >   'success-response' with boolean value false.  So far, only QGA makes
> >   use of this member.
> > +A command can be declared to support Out-Of-Band (OOB) execution.  By
> > +default, commands do not support OOB.  To declare a command to support
> 
> s/to support/that supports/
> 
> > +it, we need an extra 'allow-oob' field.  For example:
> > +
> > + { 'command': 'migrate_recover',
> > +   'data': { 'uri': 'str' }, 'allow-oob': true }
> > +
> > +To execute a command in Out-Of-Band way, we need to specify the
> > +"control" field in the request, with "run-oob" set to true. Example:
> > +
> > + => { "execute": "command-support-oob",
> > +      "arguments": { ... },
> > +      "control": { "run-oob": true } }
> > + <= { "return": { } }
> 
> This talks more about the QMP user protocol, while the rest of the document
> is about QAPI constructs.  But we do have an example of 'my-first-command'
> in the document, so I guess this is okay.
> 
> > +
> > +Without it, even the commands that support out-of-band execution will
> > +still be run In-Band.
> > +
> > +Please read the "Out-Of-Band Command Execution" section below for more
> > +information on how OOB execution works.
> > +
> > +--- About Out-Of-Band (OOB) Command Execution ---
> 
> Do we really need the paragraph mentioning a forward reference, when the
> very next thing is the item that was referenced?

Yeah, I can remove that paragraph.

For all the rest of comments (above or below, which I omitted), all of
them make sense, and I'll fix accordingly.  Thanks for reviewing.

-- 
Peter Xu

Re: [Qemu-devel] [PATCH v7 09/23] monitor: allow using IO thread for parsing

[Stefan Hajnoczi]

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On Wed, Jan 24, 2018 at 01:39:43PM +0800, Peter Xu wrote:
> @@ -4034,12 +4044,29 @@ static void sortcmdlist(void)
>      qsort((void *)info_cmds, array_num, elem_size, compare_mon_cmd);
>  }
>  
> +static GMainContext *monitor_io_context_get(void)
> +{
> +    return iothread_get_g_main_context(mon_global.mon_iothread);
> +}
> +
> +static AioContext *monitor_aio_context_get(void)
> +{
> +    return iothread_get_aio_context(mon_global.mon_iothread);
> +}

Please follow the X_get_Y() naming convention instead of X_Y_get().  For
example, see qemu_get_aio_context() and iothread_get_aio_context().

> @@ -4082,11 +4109,41 @@ void error_vprintf_unless_qmp(const char *fmt, va_list ap)
>      }
>  }
>  
> +static void monitor_list_append(Monitor *mon)
> +{
> +    qemu_mutex_lock(&monitor_lock);
> +    QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
> +    qemu_mutex_unlock(&monitor_lock);
> +}
> +
> +static void monitor_qmp_setup_handlers(void *data)

BH functions are usually declared like this:

  static void X_bh(void *opaque)

This way it's immediately clear that this function is invoked as a BH.

I suggest renaming the function to monitor_qmp_setup_handlers_bh().
Using 'opaque' instead of 'data' is common, too.

> @@ -4099,24 +4156,55 @@ void monitor_init(Chardev *chr, int flags)
>      }
>  
>      if (monitor_is_qmp(mon)) {
> -        qemu_chr_fe_set_handlers(&mon->chr, monitor_can_read, monitor_qmp_read,
> -                                 monitor_qmp_event, NULL, mon, NULL, true);
>          qemu_chr_fe_set_echo(&mon->chr, true);
>          json_message_parser_init(&mon->qmp.parser, handle_qmp_command);
> +        if (mon->use_io_thr) {
> +            /*
> +             * It's possible that we already have an IOWatchPoll
> +             * registered for the Chardev during chardev_init_func().

When does this happen?

This seems like a hack that breaks when certain -chardev options are
used.  For example, what happens if the chardev is a TCP connection with
reconnect=5.  In that case the socket will be connecting asynchronously
and we cannot just remove the fd watch.

How does this interact with TCP listen chardevs?  It looks like the
listener socket uses the main loop (see tcp_chr_disconnect()).

I'm worried that the chardev layer isn't thread-safe and you haven't
added anything to protect it or at least refuse to run in unsafe
conditions.

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Re: [Qemu-devel] [PATCH v7 10/23] qmp: introduce QMPCapability

[Stefan Hajnoczi]

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On Wed, Jan 24, 2018 at 01:39:44PM +0800, Peter Xu wrote:
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 5c06745c79..2490d5188e 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -102,21 +102,47 @@
>  #
>  # Enable QMP capabilities.
>  #
> -# Arguments: None.
> +# Arguments:
> +#
> +# @enable:    List of QMPCapabilities to enable, which is optional.
> +#             Client must not enable any capability that is not
> +#             mentioned in QMP greeting message.

qapi-schema.json uses full sentences so I've added missing articles to
the text.  I also changed s/QMPCapabilities/QMPCapability values/ to
avoid confusion about the type name:

  An optional list of QMPCapability values to enable.  The client must
  not enable any capability that is not mentioned in the QMP greeting
  message.

>  #
>  # Example:
>  #
> -# -> { "execute": "qmp_capabilities" }
> +# -> { "execute": "qmp_capabilities",
> +#      "arguments": { "enable": [ "oob" ] } }
>  # <- { "return": {} }
>  #
>  # Notes: This command is valid exactly when first connecting: it must be
>  # issued before any other command will be accepted, and will fail once the
>  # monitor is accepting other commands. (see qemu docs/interop/qmp-spec.txt)
>  #
> +# QMP client needs to explicitly enable QMP capabilities, otherwise

s/QMP client/The QMP client/

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Re: [Qemu-devel] [PATCH v7 12/23] monitor: let suspend_cnt be thread safe

[Stefan Hajnoczi]

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On Wed, Jan 24, 2018 at 01:39:46PM +0800, Peter Xu wrote:
> @@ -3996,7 +3996,7 @@ int monitor_suspend(Monitor *mon)
>  {
>      if (!mon->rs)
>          return -ENOTTY;

Does this mean that QMP monitors like -qmp unix:/tmp/foo,server,nowait
will not use suspend_cnt?

I thought the point was to use suspend_cnt for QMP monitors too.

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Re: [Qemu-devel] [PATCH v7 12/23] monitor: let suspend_cnt be thread safe

[Stefan Hajnoczi]

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Nevermind, I see the next patch adds QMP support.

Stefan

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Re: [Qemu-devel] [PATCH v7 12/23] monitor: let suspend_cnt be thread safe

[Stefan Hajnoczi]

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On Wed, Jan 24, 2018 at 01:39:46PM +0800, Peter Xu wrote:
> Monitor code now can be run in more than one thread.  Let it be thread
> safe when accessing suspend_cnt counter.
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  monitor.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [Qemu-devel] [PATCH v7 13/23] monitor: let suspend/resume work even with QMPs

[Stefan Hajnoczi]

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On Wed, Jan 24, 2018 at 01:39:47PM +0800, Peter Xu wrote:
> diff --git a/monitor.c b/monitor.c
> index 60bcf67b3a..76137ba2a4 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -246,6 +246,21 @@ static inline bool monitor_is_qmp(const Monitor *mon)
>      return (mon->flags & MONITOR_USE_CONTROL);
>  }
>  
> +/**
> + * Whether @mon is using readline?  Note: not all HMP monitors can are
> + * using readline, e.g., gdbserver has non-interactive HMP monitor, so

s/can are using/use/

s/has non-interactive HMP monitor/has a non-interactive HMP monitor/

> @@ -3994,19 +4009,43 @@ static void monitor_command_cb(void *opaque, const char *cmdline,
>  
>  int monitor_suspend(Monitor *mon)
>  {
> -    if (!mon->rs)
> +    if (monitor_is_hmp_non_interactive(mon)) {
>          return -ENOTTY;
> +    }
> +
> +    if (monitor_is_qmp(mon)) {
> +        /*
> +         * Kick iothread to make sure this takes effect.  It'll be
> +         * evaluated again in prepare() of the watch object.
> +         */
> +        aio_notify(iothread_get_aio_context(mon_global.mon_iothread));

This must be done after incrementing suspend_cnt to avoid the race
condition between the iothread and our thread.

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Re: [Qemu-devel] [PATCH v7 14/23] monitor: separate QMP parser and dispatcher

[Stefan Hajnoczi]

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On Wed, Jan 24, 2018 at 01:39:48PM +0800, Peter Xu wrote:
> Originally QMP goes through these steps:
> 
>   JSON Parser --> QMP Dispatcher --> Respond
>       /|\    (2)                (3)     |
>    (1) |                               \|/ (4)
>        +---------  main thread  --------+
> 
> This patch does this:
> 
>   JSON Parser     QMP Dispatcher --> Respond
>       /|\ |           /|\       (4)     |
>        |  | (2)        | (3)            |  (5)
>    (1) |  +----->      |               \|/
>        +---------  main thread  <-------+
> 
> So the parsing job and the dispatching job is isolated now.  It gives us
> a chance in following up patches to totally move the parser outside.
> 
> The isolation is done using one QEMUBH. Only one dispatcher QEMUBH is
> used for all the monitors.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  monitor.c | 201 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 178 insertions(+), 23 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [Qemu-devel] [PATCH v7 15/23] qmp: add new event "command-dropped"

[Stefan Hajnoczi]

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On Wed, Jan 24, 2018 at 01:39:49PM +0800, Peter Xu wrote:
> This event will be emitted if one QMP command is dropped.  Along,
> declare an enum for the reasons.
> 
> Reviewed-by: Fam Zheng <famz@redhat.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  qapi-schema.json | 37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [Qemu-devel] [PATCH v7 16/23] monitor: send event when command queue full

[Stefan Hajnoczi]

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On Wed, Jan 24, 2018 at 01:39:50PM +0800, Peter Xu wrote:
> Set maximum QMP command queue length to 8.  If queue full, instead of
> queue the command, we directly return a "command-dropped" event, telling
> client that specific command is dropped.
> 
> Note that this flow control mechanism is only valid if OOB is enabled.
> If it's not, the effective queue length will always be 1, which strictly
> follows original behavior of QMP command handling (which never drop
> messages).
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  monitor.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [Qemu-devel] [PATCH v7 18/23] qmp: support out-of-band (oob) execution

[Stefan Hajnoczi]

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On Wed, Jan 24, 2018 at 01:39:52PM +0800, Peter Xu wrote:
> Having "allow-oob" to true for a command does not mean that this command
> will always be run in out-of-band mode.  The out-of-band quick path will
> only be executed if we specify the extra "run-oob" flag when sending the
> QMP request:
> 
>     { "execute":   "command-that-allows-oob",
>       "arguments": { ... },
>       "control":   { "run-oob": true } }
> 
> The "control" key is introduced to store this extra flag.  "control"
> field is used to store arguments that are shared by all the commands,
> rather than command specific arguments.  Let "run-oob" be the first.
> 
> Note that in the patch I exported qmp_dispatch_check_obj() to be used to
> check the request earlier, and at the same time allowed "id" field to be
> there since actually we always allow that.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  include/qapi/qmp/dispatch.h |  2 ++
>  monitor.c                   | 84 ++++++++++++++++++++++++++++++++++++++++-----
>  qapi/qmp-dispatch.c         | 32 ++++++++++++++++-
>  trace-events                |  2 ++
>  4 files changed, 110 insertions(+), 10 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [Qemu-devel] [PATCH v7 19/23] qmp: isolate responses into io thread

[Stefan Hajnoczi]

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On Wed, Jan 24, 2018 at 01:39:53PM +0800, Peter Xu wrote:
> For those monitors who have enabled IO thread, we'll offload the
> responding procedure into IO thread.  The main reason is that chardev is
> not thread safe, and we need to do all the read/write IOs in the same
> thread.  For use_io_thr=true monitors, that thread is the IO thread.
> 
> We do this isolation in similar pattern as what we have done to the
> request queue: we first create one response queue for each monitor, then
> instead of replying directly in the main thread, we queue the responses
> and kick the IO thread to do the rest of the job for us.
> 
> A funny thing after doing this is that, when the QMP clients send "quit"
> to QEMU, it's possible that we close the IOThread even earlier than
> replying to that "quit".  So another thing we need to do before cleaning
> up the monitors is that we need to flush the response queue (we don't
> need to do that for command queue; after all we are quitting) to make
> sure replies for handled commands are always flushed back to clients.
> 
> Reviewed-by: Fam Zheng <famz@redhat.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  monitor.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 95 insertions(+), 1 deletion(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [Qemu-devel] [PATCH v7 00/23] QMP: out-of-band (OOB) execution support

[Stefan Hajnoczi]

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On Wed, Jan 24, 2018 at 01:39:34PM +0800, Peter Xu wrote:
> This version should have addressed all comments in previous one, also
> fixed another race condition after I addressed all the comments (a new
> race condition introduced by addressing the comments...).  For some
> more details of the race condition, please see the last entry of
> change log, and please refer to patch 9 for the code change.
> 
> I removed RFC tag from this version.  Please review.  Thanks.

I have posted comments on a few patches.

Stefan

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Re: [Qemu-devel] [PATCH v7 09/23] monitor: allow using IO thread for parsing

[Peter Xu]

On Wed, Feb 21, 2018 at 04:00:07PM +0000, Stefan Hajnoczi wrote:
> On Wed, Jan 24, 2018 at 01:39:43PM +0800, Peter Xu wrote:
> > @@ -4034,12 +4044,29 @@ static void sortcmdlist(void)
> >      qsort((void *)info_cmds, array_num, elem_size, compare_mon_cmd);
> >  }
> >  
> > +static GMainContext *monitor_io_context_get(void)
> > +{
> > +    return iothread_get_g_main_context(mon_global.mon_iothread);
> > +}
> > +
> > +static AioContext *monitor_aio_context_get(void)
> > +{
> > +    return iothread_get_aio_context(mon_global.mon_iothread);
> > +}
> 
> Please follow the X_get_Y() naming convention instead of X_Y_get().  For
> example, see qemu_get_aio_context() and iothread_get_aio_context().

Sure.

> 
> > @@ -4082,11 +4109,41 @@ void error_vprintf_unless_qmp(const char *fmt, va_list ap)
> >      }
> >  }
> >  
> > +static void monitor_list_append(Monitor *mon)
> > +{
> > +    qemu_mutex_lock(&monitor_lock);
> > +    QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
> > +    qemu_mutex_unlock(&monitor_lock);
> > +}
> > +
> > +static void monitor_qmp_setup_handlers(void *data)
> 
> BH functions are usually declared like this:
> 
>   static void X_bh(void *opaque)
> 
> This way it's immediately clear that this function is invoked as a BH.
> 
> I suggest renaming the function to monitor_qmp_setup_handlers_bh().
> Using 'opaque' instead of 'data' is common, too.

Sure.

> 
> > @@ -4099,24 +4156,55 @@ void monitor_init(Chardev *chr, int flags)
> >      }
> >  
> >      if (monitor_is_qmp(mon)) {
> > -        qemu_chr_fe_set_handlers(&mon->chr, monitor_can_read, monitor_qmp_read,
> > -                                 monitor_qmp_event, NULL, mon, NULL, true);
> >          qemu_chr_fe_set_echo(&mon->chr, true);
> >          json_message_parser_init(&mon->qmp.parser, handle_qmp_command);
> > +        if (mon->use_io_thr) {
> > +            /*
> > +             * It's possible that we already have an IOWatchPoll
> > +             * registered for the Chardev during chardev_init_func().
> 
> When does this happen?
> 
> This seems like a hack that breaks when certain -chardev options are
> used.  For example, what happens if the chardev is a TCP connection with
> reconnect=5.  In that case the socket will be connecting asynchronously
> and we cannot just remove the fd watch.
> 
> How does this interact with TCP listen chardevs?  It looks like the
> listener socket uses the main loop (see tcp_chr_disconnect()).
> 
> I'm worried that the chardev layer isn't thread-safe and you haven't
> added anything to protect it or at least refuse to run in unsafe
> conditions.

Indeed, I did some more reading and noticed that the TCP typed chardev
is really special.

Firstly there can be the QIO thread that handles sync connecting when
"reconnect" is setup (I don't really understand why we only need the
threads when reconnect != 0, but anyway, I'll just assume we need the
threads).  It's done in qmp_chardev_open_socket().

Secondly, TCP can support TLS or TELNET (tcp_chr_new_client() handles
the main logic of it), so there can be actually more than one GSource
created for a single TCP chardev.  Meanwhile, the
chr_update_read_handler() calls never handles the re-setup of those
special GSources (TLS/TELNET), only the common GSource of TCP stream
read/write.

And the whole TCP channel is based on QIO stuff, which means I need to
add non-default context support to QIO stuff too...  That's mostly
about qio_channel_add_watch().  I may need to pass in context
information, and switch to GSource for that function instead of the
old tags, just like what I did to chardev in general.

I'll think about these.  I may possibly need some pre-requisite and
separated patches to fix existing problems before going on with OOB
again.

This is the worst thing I'd like to see - "surprises". :(

Thanks,

-- 
Peter Xu

Re: [Qemu-devel] [PATCH v7 10/23] qmp: introduce QMPCapability

[Peter Xu]

On Wed, Feb 21, 2018 at 04:17:18PM +0000, Stefan Hajnoczi wrote:
> On Wed, Jan 24, 2018 at 01:39:44PM +0800, Peter Xu wrote:
> > diff --git a/qapi-schema.json b/qapi-schema.json
> > index 5c06745c79..2490d5188e 100644
> > --- a/qapi-schema.json
> > +++ b/qapi-schema.json
> > @@ -102,21 +102,47 @@
> >  #
> >  # Enable QMP capabilities.
> >  #
> > -# Arguments: None.
> > +# Arguments:
> > +#
> > +# @enable:    List of QMPCapabilities to enable, which is optional.
> > +#             Client must not enable any capability that is not
> > +#             mentioned in QMP greeting message.
> 
> qapi-schema.json uses full sentences so I've added missing articles to
> the text.  I also changed s/QMPCapabilities/QMPCapability values/ to
> avoid confusion about the type name:
> 
>   An optional list of QMPCapability values to enable.  The client must
>   not enable any capability that is not mentioned in the QMP greeting
>   message.
> 
> >  #
> >  # Example:
> >  #
> > -# -> { "execute": "qmp_capabilities" }
> > +# -> { "execute": "qmp_capabilities",
> > +#      "arguments": { "enable": [ "oob" ] } }
> >  # <- { "return": {} }
> >  #
> >  # Notes: This command is valid exactly when first connecting: it must be
> >  # issued before any other command will be accepted, and will fail once the
> >  # monitor is accepting other commands. (see qemu docs/interop/qmp-spec.txt)
> >  #
> > +# QMP client needs to explicitly enable QMP capabilities, otherwise
> 
> s/QMP client/The QMP client/

Thanks;  Fixing them all.

-- 
Peter Xu

Re: [Qemu-devel] [PATCH v7 13/23] monitor: let suspend/resume work even with QMPs

[Peter Xu]

On Wed, Feb 21, 2018 at 04:50:58PM +0000, Stefan Hajnoczi wrote:
> On Wed, Jan 24, 2018 at 01:39:47PM +0800, Peter Xu wrote:
> > diff --git a/monitor.c b/monitor.c
> > index 60bcf67b3a..76137ba2a4 100644
> > --- a/monitor.c
> > +++ b/monitor.c
> > @@ -246,6 +246,21 @@ static inline bool monitor_is_qmp(const Monitor *mon)
> >      return (mon->flags & MONITOR_USE_CONTROL);
> >  }
> >  
> > +/**
> > + * Whether @mon is using readline?  Note: not all HMP monitors can are
> > + * using readline, e.g., gdbserver has non-interactive HMP monitor, so
> 
> s/can are using/use/
> 
> s/has non-interactive HMP monitor/has a non-interactive HMP monitor/
> 
> > @@ -3994,19 +4009,43 @@ static void monitor_command_cb(void *opaque, const char *cmdline,
> >  
> >  int monitor_suspend(Monitor *mon)
> >  {
> > -    if (!mon->rs)
> > +    if (monitor_is_hmp_non_interactive(mon)) {
> >          return -ENOTTY;
> > +    }
> > +
> > +    if (monitor_is_qmp(mon)) {
> > +        /*
> > +         * Kick iothread to make sure this takes effect.  It'll be
> > +         * evaluated again in prepare() of the watch object.
> > +         */
> > +        aio_notify(iothread_get_aio_context(mon_global.mon_iothread));
> 
> This must be done after incrementing suspend_cnt to avoid the race
> condition between the iothread and our thread.

Fixed both places.  Thanks,

-- 
Peter Xu

Re: [Qemu-devel] [PATCH v7 09/23] monitor: allow using IO thread for parsing

[Stefan Hajnoczi]

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On Thu, Feb 22, 2018 at 06:01:19PM +0800, Peter Xu wrote:
> On Wed, Feb 21, 2018 at 04:00:07PM +0000, Stefan Hajnoczi wrote:
> > On Wed, Jan 24, 2018 at 01:39:43PM +0800, Peter Xu wrote:
> > > @@ -4099,24 +4156,55 @@ void monitor_init(Chardev *chr, int flags)
> > >      }
> > >  
> > >      if (monitor_is_qmp(mon)) {
> > > -        qemu_chr_fe_set_handlers(&mon->chr, monitor_can_read, monitor_qmp_read,
> > > -                                 monitor_qmp_event, NULL, mon, NULL, true);
> > >          qemu_chr_fe_set_echo(&mon->chr, true);
> > >          json_message_parser_init(&mon->qmp.parser, handle_qmp_command);
> > > +        if (mon->use_io_thr) {
> > > +            /*
> > > +             * It's possible that we already have an IOWatchPoll
> > > +             * registered for the Chardev during chardev_init_func().
> > 
> > When does this happen?
> > 
> > This seems like a hack that breaks when certain -chardev options are
> > used.  For example, what happens if the chardev is a TCP connection with
> > reconnect=5.  In that case the socket will be connecting asynchronously
> > and we cannot just remove the fd watch.
> > 
> > How does this interact with TCP listen chardevs?  It looks like the
> > listener socket uses the main loop (see tcp_chr_disconnect()).
> > 
> > I'm worried that the chardev layer isn't thread-safe and you haven't
> > added anything to protect it or at least refuse to run in unsafe
> > conditions.
> 
> Indeed, I did some more reading and noticed that the TCP typed chardev
> is really special.
> 
> Firstly there can be the QIO thread that handles sync connecting when
> "reconnect" is setup (I don't really understand why we only need the
> threads when reconnect != 0, but anyway, I'll just assume we need the
> threads).  It's done in qmp_chardev_open_socket().
> 
> Secondly, TCP can support TLS or TELNET (tcp_chr_new_client() handles
> the main logic of it), so there can be actually more than one GSource
> created for a single TCP chardev.  Meanwhile, the
> chr_update_read_handler() calls never handles the re-setup of those
> special GSources (TLS/TELNET), only the common GSource of TCP stream
> read/write.
> 
> And the whole TCP channel is based on QIO stuff, which means I need to
> add non-default context support to QIO stuff too...  That's mostly
> about qio_channel_add_watch().  I may need to pass in context
> information, and switch to GSource for that function instead of the
> old tags, just like what I did to chardev in general.
> 
> I'll think about these.  I may possibly need some pre-requisite and
> separated patches to fix existing problems before going on with OOB
> again.
> 
> This is the worst thing I'd like to see - "surprises". :(

Yes, this feature is more involved than anyone thought at the beginning.

Stefan

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Re: [Qemu-devel] [PATCH v7 09/23] monitor: allow using IO thread for parsing

[Daniel P. Berrangé]

On Thu, Feb 22, 2018 at 06:01:19PM +0800, Peter Xu wrote:
> On Wed, Feb 21, 2018 at 04:00:07PM +0000, Stefan Hajnoczi wrote:
> > On Wed, Jan 24, 2018 at 01:39:43PM +0800, Peter Xu wrote:
> > > @@ -4034,12 +4044,29 @@ static void sortcmdlist(void)
> > >      qsort((void *)info_cmds, array_num, elem_size, compare_mon_cmd);
> > >  }
> > >  
> > > +static GMainContext *monitor_io_context_get(void)
> > > +{
> > > +    return iothread_get_g_main_context(mon_global.mon_iothread);
> > > +}
> > > +
> > > +static AioContext *monitor_aio_context_get(void)
> > > +{
> > > +    return iothread_get_aio_context(mon_global.mon_iothread);
> > > +}
> > 
> > Please follow the X_get_Y() naming convention instead of X_Y_get().  For
> > example, see qemu_get_aio_context() and iothread_get_aio_context().
> 
> Sure.
> 
> > 
> > > @@ -4082,11 +4109,41 @@ void error_vprintf_unless_qmp(const char *fmt, va_list ap)
> > >      }
> > >  }
> > >  
> > > +static void monitor_list_append(Monitor *mon)
> > > +{
> > > +    qemu_mutex_lock(&monitor_lock);
> > > +    QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
> > > +    qemu_mutex_unlock(&monitor_lock);
> > > +}
> > > +
> > > +static void monitor_qmp_setup_handlers(void *data)
> > 
> > BH functions are usually declared like this:
> > 
> >   static void X_bh(void *opaque)
> > 
> > This way it's immediately clear that this function is invoked as a BH.
> > 
> > I suggest renaming the function to monitor_qmp_setup_handlers_bh().
> > Using 'opaque' instead of 'data' is common, too.
> 
> Sure.
> 
> > 
> > > @@ -4099,24 +4156,55 @@ void monitor_init(Chardev *chr, int flags)
> > >      }
> > >  
> > >      if (monitor_is_qmp(mon)) {
> > > -        qemu_chr_fe_set_handlers(&mon->chr, monitor_can_read, monitor_qmp_read,
> > > -                                 monitor_qmp_event, NULL, mon, NULL, true);
> > >          qemu_chr_fe_set_echo(&mon->chr, true);
> > >          json_message_parser_init(&mon->qmp.parser, handle_qmp_command);
> > > +        if (mon->use_io_thr) {
> > > +            /*
> > > +             * It's possible that we already have an IOWatchPoll
> > > +             * registered for the Chardev during chardev_init_func().
> > 
> > When does this happen?
> > 
> > This seems like a hack that breaks when certain -chardev options are
> > used.  For example, what happens if the chardev is a TCP connection with
> > reconnect=5.  In that case the socket will be connecting asynchronously
> > and we cannot just remove the fd watch.
> > 
> > How does this interact with TCP listen chardevs?  It looks like the
> > listener socket uses the main loop (see tcp_chr_disconnect()).
> > 
> > I'm worried that the chardev layer isn't thread-safe and you haven't
> > added anything to protect it or at least refuse to run in unsafe
> > conditions.
> 
> Indeed, I did some more reading and noticed that the TCP typed chardev
> is really special.
> 
> Firstly there can be the QIO thread that handles sync connecting when
> "reconnect" is setup (I don't really understand why we only need the
> threads when reconnect != 0, but anyway, I'll just assume we need the
> threads).  It's done in qmp_chardev_open_socket().
> 
> Secondly, TCP can support TLS or TELNET (tcp_chr_new_client() handles
> the main logic of it), so there can be actually more than one GSource
> created for a single TCP chardev.  Meanwhile, the
> chr_update_read_handler() calls never handles the re-setup of those
> special GSources (TLS/TELNET), only the common GSource of TCP stream
> read/write.
> 
> And the whole TCP channel is based on QIO stuff, which means I need to
> add non-default context support to QIO stuff too...  That's mostly
> about qio_channel_add_watch().  I may need to pass in context
> information, and switch to GSource for that function instead of the
> old tags, just like what I did to chardev in general.

Rather than changing qio_channel_add_watch() which affects all callers,
just add a qio_channel_add_watch_full() variant which includes  GMainContext
as an extra arg

Regards,
Daniel
-- 
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Re: [Qemu-devel] [PATCH v7 09/23] monitor: allow using IO thread for parsing

[Peter Xu]

On Thu, Feb 22, 2018 at 03:50:47PM +0000, Daniel P. Berrangé wrote:
> On Thu, Feb 22, 2018 at 06:01:19PM +0800, Peter Xu wrote:
> > On Wed, Feb 21, 2018 at 04:00:07PM +0000, Stefan Hajnoczi wrote:
> > > On Wed, Jan 24, 2018 at 01:39:43PM +0800, Peter Xu wrote:
> > > > @@ -4034,12 +4044,29 @@ static void sortcmdlist(void)
> > > >      qsort((void *)info_cmds, array_num, elem_size, compare_mon_cmd);
> > > >  }
> > > >  
> > > > +static GMainContext *monitor_io_context_get(void)
> > > > +{
> > > > +    return iothread_get_g_main_context(mon_global.mon_iothread);
> > > > +}
> > > > +
> > > > +static AioContext *monitor_aio_context_get(void)
> > > > +{
> > > > +    return iothread_get_aio_context(mon_global.mon_iothread);
> > > > +}
> > > 
> > > Please follow the X_get_Y() naming convention instead of X_Y_get().  For
> > > example, see qemu_get_aio_context() and iothread_get_aio_context().
> > 
> > Sure.
> > 
> > > 
> > > > @@ -4082,11 +4109,41 @@ void error_vprintf_unless_qmp(const char *fmt, va_list ap)
> > > >      }
> > > >  }
> > > >  
> > > > +static void monitor_list_append(Monitor *mon)
> > > > +{
> > > > +    qemu_mutex_lock(&monitor_lock);
> > > > +    QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
> > > > +    qemu_mutex_unlock(&monitor_lock);
> > > > +}
> > > > +
> > > > +static void monitor_qmp_setup_handlers(void *data)
> > > 
> > > BH functions are usually declared like this:
> > > 
> > >   static void X_bh(void *opaque)
> > > 
> > > This way it's immediately clear that this function is invoked as a BH.
> > > 
> > > I suggest renaming the function to monitor_qmp_setup_handlers_bh().
> > > Using 'opaque' instead of 'data' is common, too.
> > 
> > Sure.
> > 
> > > 
> > > > @@ -4099,24 +4156,55 @@ void monitor_init(Chardev *chr, int flags)
> > > >      }
> > > >  
> > > >      if (monitor_is_qmp(mon)) {
> > > > -        qemu_chr_fe_set_handlers(&mon->chr, monitor_can_read, monitor_qmp_read,
> > > > -                                 monitor_qmp_event, NULL, mon, NULL, true);
> > > >          qemu_chr_fe_set_echo(&mon->chr, true);
> > > >          json_message_parser_init(&mon->qmp.parser, handle_qmp_command);
> > > > +        if (mon->use_io_thr) {
> > > > +            /*
> > > > +             * It's possible that we already have an IOWatchPoll
> > > > +             * registered for the Chardev during chardev_init_func().
> > > 
> > > When does this happen?
> > > 
> > > This seems like a hack that breaks when certain -chardev options are
> > > used.  For example, what happens if the chardev is a TCP connection with
> > > reconnect=5.  In that case the socket will be connecting asynchronously
> > > and we cannot just remove the fd watch.
> > > 
> > > How does this interact with TCP listen chardevs?  It looks like the
> > > listener socket uses the main loop (see tcp_chr_disconnect()).
> > > 
> > > I'm worried that the chardev layer isn't thread-safe and you haven't
> > > added anything to protect it or at least refuse to run in unsafe
> > > conditions.
> > 
> > Indeed, I did some more reading and noticed that the TCP typed chardev
> > is really special.
> > 
> > Firstly there can be the QIO thread that handles sync connecting when
> > "reconnect" is setup (I don't really understand why we only need the
> > threads when reconnect != 0, but anyway, I'll just assume we need the
> > threads).  It's done in qmp_chardev_open_socket().
> > 
> > Secondly, TCP can support TLS or TELNET (tcp_chr_new_client() handles
> > the main logic of it), so there can be actually more than one GSource
> > created for a single TCP chardev.  Meanwhile, the
> > chr_update_read_handler() calls never handles the re-setup of those
> > special GSources (TLS/TELNET), only the common GSource of TCP stream
> > read/write.
> > 
> > And the whole TCP channel is based on QIO stuff, which means I need to
> > add non-default context support to QIO stuff too...  That's mostly
> > about qio_channel_add_watch().  I may need to pass in context
> > information, and switch to GSource for that function instead of the
> > old tags, just like what I did to chardev in general.
> 
> Rather than changing qio_channel_add_watch() which affects all callers,
> just add a qio_channel_add_watch_full() variant which includes  GMainContext
> as an extra arg

Yeh, will do.  Thanks,

-- 
Peter Xu

Re: [Qemu-devel] [PATCH v7 17/23] qapi: introduce new cmd option "allow-oob"

[Igor Mammedov]

On Wed, 24 Jan 2018 13:39:51 +0800
Peter Xu <peterx@redhat.com> wrote:

> Here "oob" stands for "Out-Of-Band".  When "allow-oob" is set, it means
> the command allows out-of-band execution.
> 
> The "oob" idea is proposed by Markus Armbruster in following thread:
> 
>   https://lists.gnu.org/archive/html/qemu-devel/2017-09/msg02057.html
> 
> This new "allow-oob" boolean will be exposed by "query-qmp-schema" as
> well for command entries, so that QMP clients can know which command can
> be used as out-of-band calls. For example the command "migrate"
> originally looks like:
> 
>   {"name": "migrate", "ret-type": "17", "meta-type": "command",
>    "arg-type": "86"}
> 
> And it'll be changed into:
> 
>   {"name": "migrate", "ret-type": "17", "allow-oob": false,
>    "meta-type": "command", "arg-type": "86"}
> 
> This patch only provides the QMP interface level changes.  It does not
> contains the real out-of-band execution implementation yet.
> 
> Suggested-by: Markus Armbruster <armbru@redhat.com>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> Reviewed-by: Fam Zheng <famz@redhat.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  include/qapi/qmp/dispatch.h    |  1 +
>  qapi/introspect.json           |  6 +++++-
>  scripts/qapi-commands.py       | 19 ++++++++++++++-----
>  scripts/qapi-introspect.py     | 10 ++++++++--
>  scripts/qapi.py                | 15 ++++++++++-----
>  scripts/qapi2texi.py           |  2 +-
>  tests/qapi-schema/test-qapi.py |  2 +-
>  7 files changed, 40 insertions(+), 15 deletions(-)
> 
> diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
> index 20578dcd48..b76798800c 100644
> --- a/include/qapi/qmp/dispatch.h
> +++ b/include/qapi/qmp/dispatch.h
> @@ -23,6 +23,7 @@ typedef enum QmpCommandOptions
>  {
>      QCO_NO_OPTIONS = 0x0,
>      QCO_NO_SUCCESS_RESP = 0x1,
> +    QCO_ALLOW_OOB = 0x2,
Options are essentially bitmask,
so using shift for value would be more explicit way to express it.

  QCO_ALLOW_OOB = (1U << 1)

>  } QmpCommandOptions;
>  
>  typedef struct QmpCommand
[...]

Re: [Qemu-devel] [PATCH v7 17/23] qapi: introduce new cmd option "allow-oob"

[Peter Xu]

On Thu, Mar 08, 2018 at 11:04:13AM +0100, Igor Mammedov wrote:
> On Wed, 24 Jan 2018 13:39:51 +0800
> Peter Xu <peterx@redhat.com> wrote:
> 
> > Here "oob" stands for "Out-Of-Band".  When "allow-oob" is set, it means
> > the command allows out-of-band execution.
> > 
> > The "oob" idea is proposed by Markus Armbruster in following thread:
> > 
> >   https://lists.gnu.org/archive/html/qemu-devel/2017-09/msg02057.html
> > 
> > This new "allow-oob" boolean will be exposed by "query-qmp-schema" as
> > well for command entries, so that QMP clients can know which command can
> > be used as out-of-band calls. For example the command "migrate"
> > originally looks like:
> > 
> >   {"name": "migrate", "ret-type": "17", "meta-type": "command",
> >    "arg-type": "86"}
> > 
> > And it'll be changed into:
> > 
> >   {"name": "migrate", "ret-type": "17", "allow-oob": false,
> >    "meta-type": "command", "arg-type": "86"}
> > 
> > This patch only provides the QMP interface level changes.  It does not
> > contains the real out-of-band execution implementation yet.
> > 
> > Suggested-by: Markus Armbruster <armbru@redhat.com>
> > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> > Reviewed-by: Fam Zheng <famz@redhat.com>
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> >  include/qapi/qmp/dispatch.h    |  1 +
> >  qapi/introspect.json           |  6 +++++-
> >  scripts/qapi-commands.py       | 19 ++++++++++++++-----
> >  scripts/qapi-introspect.py     | 10 ++++++++--
> >  scripts/qapi.py                | 15 ++++++++++-----
> >  scripts/qapi2texi.py           |  2 +-
> >  tests/qapi-schema/test-qapi.py |  2 +-
> >  7 files changed, 40 insertions(+), 15 deletions(-)
> > 
> > diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
> > index 20578dcd48..b76798800c 100644
> > --- a/include/qapi/qmp/dispatch.h
> > +++ b/include/qapi/qmp/dispatch.h
> > @@ -23,6 +23,7 @@ typedef enum QmpCommandOptions
> >  {
> >      QCO_NO_OPTIONS = 0x0,
> >      QCO_NO_SUCCESS_RESP = 0x1,
> > +    QCO_ALLOW_OOB = 0x2,
> Options are essentially bitmask,
> so using shift for value would be more explicit way to express it.
> 
>   QCO_ALLOW_OOB = (1U << 1)

Yes, shifting would be more clear.  Thanks,

-- 
Peter Xu

Re: [Qemu-devel] [PATCH v7 17/23] qapi: introduce new cmd option "allow-oob"

[Peter Xu]

On Thu, Mar 08, 2018 at 11:04:13AM +0100, Igor Mammedov wrote:

[...]

> > diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
> > index 20578dcd48..b76798800c 100644
> > --- a/include/qapi/qmp/dispatch.h
> > +++ b/include/qapi/qmp/dispatch.h
> > @@ -23,6 +23,7 @@ typedef enum QmpCommandOptions
> >  {
> >      QCO_NO_OPTIONS = 0x0,
> >      QCO_NO_SUCCESS_RESP = 0x1,
> > +    QCO_ALLOW_OOB = 0x2,
> Options are essentially bitmask,
> so using shift for value would be more explicit way to express it.
> 
>   QCO_ALLOW_OOB = (1U << 1)

I'll squash the change into the patch:

diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h         
index b4cb25888f..26eb13ff41 100644                   
--- a/include/qapi/qmp/dispatch.h      
+++ b/include/qapi/qmp/dispatch.h      
@@ -20,9 +20,9 @@ typedef void (QmpCommandFunc)(QDict *, QObject **, Error **);
                                                                               
 typedef enum QmpCommandOptions        
 {                                                                             
-    QCO_NO_OPTIONS = 0x0,                                                     
-    QCO_NO_SUCCESS_RESP = 0x1,        
-    QCO_ALLOW_OOB = 0x2,                                                      
+    QCO_NO_OPTIONS            =  0x0,                                         
+    QCO_NO_SUCCESS_RESP       =  (1U << 0),                                   
+    QCO_ALLOW_OOB             =  (1U << 1),                                   
 } QmpCommandOptions;                                        
                                           
 typedef struct QmpCommand                                                     

Since the change is trivial, I'll keep r-bs for Stefan and Fam.
Anyone who thinks I shouldn't please shoot.  Thanks,

-- 
Peter Xu