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 * '-mon' is obsolete, deprecated and replaced by '-object', but -monitor, -qmp and kept as high level syntax sugar * QMP gains a concept of "close-action" which makes it possible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. 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. [1] ~~~ we did all this not because it was easy, but because we thought it would be easy ~~~ Changed in v7: - Split Chardev -> const char *chardev_id change into separate patch from QOM property addition - Copy editting of qemu-options docs - Updating of commit messages with improved wording - Remove redundant ERRP_GUARD - Improve error message wording when rejecting delete requests - Don't hardcode "gdbchrdev0" ID, allow default logic Changed in v6: - Present "ID" from QemuOpts to use for the QOM object - Use 'compat_monitorNNN' as ID if QemuOpts lacks an ID, for compat with -monitor/-qmp arg naming - Mark the Monitor class abstract when first defined - Tweaks to formatting of QAPI docs - Expand CLI docs to describe relation between -monitor and -qmp and -object. - Present object ID in error messages for prepare_delete callback - Drop API which dupes object_get_canonical_path_component - Dropped R-B on patches 01, 05, 34 Changed in v5: - Address another race when looking up monitor by ID - Refer to "line editting" when talking about HMP readline feature - Misc typos - Fix mis-placed setting of 'delete_pending' - Add test case to validate reconnecting to QMP Changed in v4: - Hold reference into BH to avoid race with auto-delete Changed in v3: - Removed unused 'dead' struct field - Make use of 'setup_pending' struct field across BH - Add missing free of chardev_id - Add missnig ERRP_GUARD in monitor_new_qmp - Misc docs typos / rephrasing - Moved docs patch to the end - Fixed docs about the default QOM ID naming for legacy monitor syntax - Fixed random sleep time calculation in tests 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: pass chardev ID into monitor constructor instead of object 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 tests/functional: add a stress test for monitor hot unplug 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 qemu-options: document new monitor-hmp and monitor-qmp objects docs: mark '-mon' as deprecated in favour of -object MAINTAINERS | 1 + backends/cryptodev.c | 12 +- backends/hostmem.c | 7 +- backends/iommufd.c | 11 +- block/throttle-groups.c | 12 +- 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 | 2 +- include/monitor/monitor.h | 26 +- 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 | 73 ++-- monitor/monitor.c | 271 ++++++++------- monitor/qmp-cmds-control.c | 12 +- monitor/qmp-cmds.c | 14 +- monitor/qmp.c | 323 +++++++++++++++--- net/can/can_core.c | 6 +- python/qemu/machine/machine.py | 4 +- qapi/qom.json | 63 ++++ qemu-options.hx | 65 +++- 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 | 4 +- system/vl.c | 19 +- tests/functional/generic/meson.build | 1 + .../generic/test_monitor_hotplug.py | 305 +++++++++++++++++ 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 | 6 +- 44 files changed, 1395 insertions(+), 332 deletions(-) create mode 100755 tests/functional/generic/test_monitor_hotplug.py -- 2.55.0