This v6 kept most of the high level design untouched, however there
are quite a few of changes that try to make the series more robust and
safe. My sincere thank to the reviewers (especially Stefan!) on all
review comments to previous one. Let's see how this version goes.
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 (27):
chardev: use backend chr context when watch for fe
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: create monitor dedicate iothread
monitor: allow to use IO thread for parsing
qmp: introduce QMPCapability
qmp: negotiate QMP capabilities
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: export qmp_dispatch_check_obj and allow "id"
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"
docs: update QMP documents for OOB commands
tests: qmp-test: verify command batching
tests: qmp-test: add oob test
chardev/char-fe.c | 2 +-
docs/devel/qapi-code-gen.txt | 70 ++++-
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 | 650 +++++++++++++++++++++++++++++++++++------
qapi-schema.json | 83 +++++-
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 +-
21 files changed, 960 insertions(+), 121 deletions(-)
--
2.14.3
