Conceptually -object and object_add/object_del should be sufficient
for essentially all QEMU configuration....if only we ported all our
internal custom backends/devices/etc to QOM. That is of course a big
job which is why it hasn't happened.
This series started with the premise that the monitor is one of the
easier areas to convert since we have no more than three classes,
a common base, and QMP and HMP subclasses[1]. So why not give it a
go and thus unlock the ability to dynamically create/delete monitors
in QMP/HMP.
This series does the conversion in a great many small steps to better
understand the implications at each stage.
The high level outcome of this series is
* HMP and QMP monitors are QOM objects, 'monitor-hmp' and
'monitor-qmp' respectively
* Both can be cold plugged and hot plugged. QMP only, can
also be hot unplugged.
* '-mon' is obsolete, deprecated and replaced by '-object',
but -monitor, -qmp and kept as high level syntax sugar
* QMP gains a concept of "close-action" which makes it
possible to mark a monitor for auto-delete.
The monitor hot-unplug code and the qtest and functional testing
code is heavily derived from a series sent by Christian Brauner
which proposed new monitor_add/monitor_del commands:
https://lists.nongnu.org/archive/html/qemu-devel/2026-04/msg01349.html
I left Christian's authorship & SoB on the patches which were
derived from his code, though the code has been refactored quite
a bit in places, so bugs are quite possibly my own. Christian,
if you prefer any changes in attribution here let me know.
Note that Christian's series allowed the use of "monitor_del"
commands against the current monitor session. ie a client could
delete the very monitor it was using. This is an awkward concept
as it needs special casing to delay the deletion to happen in
the background, such that that the QMP response to 'monitor_del'
could still be sent back. This also left the chardev was orphaned
as there's no way to run 'chardev_dev' in that usage pattern.
To provide an alternative mechanism to address the same use case,
this series introduces the 'close-action' concept mentioned above,
that allows hotplugging a monitor to service a specific task,
with the monitor being purged when the script closes its connection.
This avoids the special casing that an explicit "self deletion"
paradigm required.
While supporting hotplug of HMP was trivial, I didn't do any work
to think about hotunplug of HMP, since IMHO it is of limited value
given HMP's typical use cases.
While -mon is deprecated in favour of -object, given '-mon' is
such a significant CLI option, it is likely wise to not remove
it as quickly as our deprecation policy would otherwise allow
given the disruption that's liable to cause. It isn't a big
burden to keep it around for a long time.
[1] ~~~ we did all this not because it was easy,
but because we thought it would be easy ~~~
Christian Brauner (6):
monitor: convert from oneshot BH to persistent BH
monitor: reject attempts to delete the current monitor
monitor: protect qemu_chr_fe_accept_input with monitor lock
monitor: implement support for deleting QMP objects
tests/qtest: add tests for dynamic monitor add/remove
tests/functional: add e2e test for dynamic QMP monitor hotplug
Daniel P. Berrangé (29):
qom: replace 'can_be_deleted' with 'prepare_delete'
monitor: replace 'common' with 'parent_obj' in MonitorHMP
monitor: replace 'common' with 'parent_obj' in MonitorQMP
monitor: rename monitor_init* to monitor_new*
monitor: minimal conversion of monitors to QOM
monitor: add 'chardev' property to Monitor base class
monitor: add 'readline' property to HMP Monitor class
monitor: add 'pretty' property to QMP Monitor class
monitor: remove 'skip_flush' field
monitor: move monitor_data_(init|destroy) into QOM init/finalize
monitor: use class methods for monitor_vprintf
monitor: use class methods for monitor_qapi_event_emit
monitor: use class methods for monitor_accept_input
monitor: use class method for I/O thread request
monitor: use dynamic cast in monitor_qmp_requests_pop_any_with_lock
util: use dynamic cast in error vreport
monitor: drop unused monitor_cur_is_qmp
monitor: use dynamic cast in QMP commands
monitor: use dynamic cast in monitor_is_hmp_non_interactive
monitor: drop unused monitor_is_qmp method
monitor: eliminate monitor_is_hmp_non_interactive method
monitor: implement "user creatable" interface for adding monitors
qemu-options: document new monitor-hmp and monitor-qmp objects
tests/functional: add a stress test for monitor hot unplug
qom: add method for getting the "id" of a QOM object
qom: add trace events for user creatable create/delete APIs
monitor: add support for auto-deleting monitors upon close
tests: switch from -mon to -object monitor-qmp
docs: mark '-mon' as deprecated in favour of -object
MAINTAINERS | 1 +
backends/cryptodev.c | 10 +-
backends/hostmem.c | 5 +-
backends/iommufd.c | 10 +-
block/throttle-groups.c | 10 +-
chardev/char.c | 3 +-
docs/about/deprecated.rst | 10 +
docs/devel/writing-monitor-commands.rst | 4 +-
docs/system/arm/xenpvh.rst | 4 +-
docs/system/i386/xen.rst | 3 +-
docs/system/i386/xenpvh.rst | 4 +-
event-loop-base.c | 8 +-
gdbstub/system.c | 4 +-
include/monitor/monitor.h | 23 +-
include/qom/object.h | 10 +
include/qom/object_interfaces.h | 26 +-
include/system/event-loop-base.h | 2 +-
migration/migration-hmp-cmds.c | 5 +-
monitor/hmp-cmds.c | 7 +-
monitor/hmp.c | 181 +++++++++--
monitor/monitor-internal.h | 74 +++--
monitor/monitor.c | 261 +++++++--------
monitor/qmp-cmds-control.c | 12 +-
monitor/qmp-cmds.c | 14 +-
monitor/qmp.c | 301 +++++++++++++++---
net/can/can_core.c | 5 +-
python/qemu/machine/machine.py | 4 +-
qapi/qom.json | 62 ++++
qemu-options.hx | 53 ++-
qom/object.c | 17 +
qom/object_interfaces.c | 20 +-
qom/trace-events | 5 +
storage-daemon/qemu-storage-daemon.c | 2 +-
stubs/monitor-core.c | 5 -
stubs/monitor-internal.c | 3 +-
system/vl.c | 12 +-
tests/functional/generic/meson.build | 1 +
.../generic/test_monitor_hotplug.py | 275 ++++++++++++++++
tests/qemu-iotests/245 | 4 +-
tests/qtest/libqtest.c | 2 +-
tests/qtest/qmp-test.c | 174 ++++++++++
tests/unit/test-util-sockets.c | 1 -
tools/qemu-vnc/stubs.c | 5 -
ui/ui-hmp-cmds.c | 2 +-
util/error-report.c | 13 +-
util/main-loop.c | 5 +-
46 files changed, 1335 insertions(+), 327 deletions(-)
create mode 100755 tests/functional/generic/test_monitor_hotplug.py
--
2.54.0