The default monitor is usually a long lived object that will exist for the entire lifetime of the VM. A monitor can only service a single client at a time though, and so it might be desirable to hotplug additional monitors at runtime for specific tasks. If doing that, however, there is a need to remove the monitor when it is no longer needed. Allowing a client to run "object-del" against its own monitor adds complex edge cases, as it would be desirable to send the QMP response despite the monitor sending it being deleted. Doing "object-del" alone will also result in orphaning a character device backend instance, as there is no opportunity to run the companion "chardev-del" command. A simpler way to ensure cleanup is to add the concept of auto-deleting monitor objects. Specifically when the "CHR_EVENT_CLOSED" event is emitted, the equivalent of "object-del" + "chardev-del" can be run internally. Since the transient client has already droppped its monitor connection, there is no synchronization to be concerned about. This is implemented via a new "close-action=none|delete" property on the 'monitor-qmp' object. This concept could be extended with further actions in future, for example: * close-action=shutdown - graceful guest shutdown * close-action=terminate - immediate guest poweroff * close-action=stop - pause guest CPUs while the monitor is not connected to any client This is left as an exercise for future interested contributors. Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> --- monitor/monitor-internal.h | 3 + monitor/qmp.c | 59 +++++++++++++++++++ qapi/qom.json | 21 ++++++- qemu-options.hx | 10 +++- .../generic/test_monitor_hotplug.py | 53 +++++++++++++++-- 5 files changed, 140 insertions(+), 6 deletions(-) diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h index 2e8e5ec721..165002f535 100644 --- a/monitor/monitor-internal.h +++ b/monitor/monitor-internal.h @@ -28,6 +28,7 @@ #include "chardev/char-fe.h" #include "monitor/monitor.h" #include "qapi/qapi-types-control.h" +#include "qapi/qapi-types-qom.h" #include "qapi/qmp-registry.h" #include "qobject/json-parser.h" #include "qemu/readline.h" @@ -179,7 +180,9 @@ struct MonitorQMP { Monitor parent_obj; JSONMessageParser parser; bool pretty; + MonitorQMPCloseAction close_action; bool setup_pending; /* iothread BH has not yet set up chardev handlers */ + bool delete_pending; /* close_action has started 'delete' process */ /* * When a client connects, we're in capabilities negotiation mode. * @commands is &qmp_cap_negotiation_commands then. When command diff --git a/monitor/qmp.c b/monitor/qmp.c index d471428488..905f924ea6 100644 --- a/monitor/qmp.c +++ b/monitor/qmp.c @@ -28,6 +28,7 @@ #include "monitor-internal.h" #include "qapi/error.h" #include "qapi/qapi-commands-control.h" +#include "qapi/qapi-commands-char.h" #include "qobject/qdict.h" #include "qobject/qjson.h" #include "qobject/qlist.h" @@ -103,6 +104,20 @@ static void monitor_qmp_set_pretty(Object *obj, bool val, Error **errp) mon->pretty = val; } +static int monitor_qmp_get_close_action(Object *obj, Error **errp) +{ + MonitorQMP *mon = MONITOR_QMP(obj); + + return mon->close_action; +} + +static void monitor_qmp_set_close_action(Object *obj, int val, Error **errp) +{ + MonitorQMP *mon = MONITOR_QMP(obj); + + mon->close_action = val; +} + static void monitor_qmp_emit_event(Monitor *mon, QAPIEvent event, QDict *qdict); static bool monitor_qmp_requires_iothread(const Monitor *mon); static void monitor_qmp_complete(UserCreatable *uc, Error **errp); @@ -117,6 +132,11 @@ static void monitor_qmp_class_init(ObjectClass *cls, const void *data) object_class_property_add_bool(cls, "pretty", monitor_qmp_get_pretty, monitor_qmp_set_pretty); + object_class_property_add_enum(cls, "close-action", + "MonitorQMPCloseAction", + &MonitorQMPCloseAction_lookup, + monitor_qmp_get_close_action, + monitor_qmp_set_close_action); moncls->emit_event = monitor_qmp_emit_event; moncls->requires_iothread = monitor_qmp_requires_iothread; @@ -550,11 +570,33 @@ static QDict *qmp_greeting(MonitorQMP *mon) ver, cap_list); } +static void monitor_qmp_self_delete_bh(void *opaque) +{ + MonitorQMP *mon = opaque; + g_autofree char *mon_id = object_property_get_child_name( + object_get_objects_root(), OBJECT(mon)); + g_autofree char *chardev_id = g_strdup(mon->parent_obj.chardev_id); + Error *local_error = NULL; + + g_assert(mon_id); + + user_creatable_del(mon_id, &local_error); + if (local_error != NULL) { + error_report_err(local_error); + } else { + qmp_chardev_remove(chardev_id, NULL); + } +} + static void monitor_qmp_event(void *opaque, QEMUChrEvent event) { QDict *data; MonitorQMP *mon = opaque; + if (mon->delete_pending) { + return; + } + switch (event) { case CHR_EVENT_OPENED: WITH_QEMU_LOCK_GUARD(&mon->parent_obj.mon_lock) { @@ -577,6 +619,23 @@ static void monitor_qmp_event(void *opaque, QEMUChrEvent event) json_message_parser_init(&mon->parser, handle_qmp_command, mon, NULL); monitor_fdsets_cleanup(); + switch (mon->close_action) { + case MONITOR_QMP_CLOSE_ACTION_NONE: + break; /* nada */ + case MONITOR_QMP_CLOSE_ACTION_DELETE: + mon->delete_pending = true; + /* + * Do NOT run in the AIO context associated with the + * monitor. We need to run in the default AIO context + * which is the same context in which 'qmp_object_del' + * will execute + */ + aio_bh_schedule_oneshot(qemu_get_aio_context(), + monitor_qmp_self_delete_bh, mon); + break; + default: + g_assert_not_reached(); + } break; case CHR_EVENT_BREAK: case CHR_EVENT_MUX_IN: diff --git a/qapi/qom.json b/qapi/qom.json index 6ed510858e..63335b8fd0 100644 --- a/qapi/qom.json +++ b/qapi/qom.json @@ -1213,18 +1213,37 @@ 'base': 'MonitorProperties', 'data': { '*readline': 'bool' } } + +## +# @MonitorQMPCloseAction: +# +# Action to take when the character device backend is +# closed. +# +# @none: take no action (the default) +# @delete: delete both the 'monitor-qmp' object and its associated +# character device backend object +# +# Since 11.1 +## +{ 'enum' : 'MonitorQMPCloseAction', + 'data': ['none', 'delete'] } + ## # @MonitorQMPProperties: # # Properties for the QMP monitor # # @pretty: whether to pretty print JSON responses (default: disabled) +# @close-action: action to take when the character device backend +# is closed (default: none) # # Since: 11.1 ## { 'struct': 'MonitorQMPProperties', 'base': 'MonitorProperties', - 'data': { '*pretty': 'bool' } } + 'data': { '*pretty': 'bool', + '*close-action': 'MonitorQMPCloseAction' } } ## # @ObjectType: diff --git a/qemu-options.hx b/qemu-options.hx index 031417b79d..848a53ea34 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -5730,7 +5730,7 @@ SRST controls whether the monitor provides interactive prompts - ``-object monitor-qmp,id=id,chardev=chardev_id,pretty=on|off`` + ``-object monitor-qmp,id=id,chardev=chardev_id,pretty=on|off,close-action=none|delete`` Set up a monitor running the QEMU Monitor Protocol, connected to the chardev ``chrid``. @@ -5747,6 +5747,14 @@ SRST constrained to a single line without extraneous whitespace. + The ``close-action`` parameter, which defaults to ``none``, + controls what happens when the connection to the monitor + is terminated by the user. If set to ``delete``, then the + ``monitor-qmp`` object and its associated character + device are both immediately deleted. This can be useful + if an extra monitor was hotplugged for a specific task + and should be unplugged when completed. + ``-object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align,offset=offset,readonly=on|off,rom=on|off|auto`` Creates a memory file backend object, which can be used to back the guest RAM with huge pages. diff --git a/tests/functional/generic/test_monitor_hotplug.py b/tests/functional/generic/test_monitor_hotplug.py index 03087faafc..f7d72a77c2 100755 --- a/tests/functional/generic/test_monitor_hotplug.py +++ b/tests/functional/generic/test_monitor_hotplug.py @@ -25,7 +25,7 @@ def setUp(self): sock_dir = self.socket_dir() self._sock_path = os.path.join(sock_dir.name, 'hotplug.sock') - def _add_monitor(self): + def _add_monitor(self, autodelete=False): """Create a chardev + monitor and return the socket path.""" sock = self._sock_path self.vm.cmd('chardev-add', id='hotplug-chr', backend={ @@ -39,9 +39,15 @@ def _add_monitor(self): 'wait': False, } }) - self.vm.cmd('object-add', id='hotplug-mon', - qom_type='monitor-qmp', - chardev='hotplug-chr') + if autodelete: + self.vm.cmd('object-add', id='hotplug-mon', + qom_type='monitor-qmp', + chardev='hotplug-chr', + close_action='delete') + else: + self.vm.cmd('object-add', id='hotplug-mon', + qom_type='monitor-qmp', + chardev='hotplug-chr') return sock def _remove_monitor(self): @@ -118,6 +124,45 @@ def test_self_removal(self): # Clean up the chardev self.vm.cmd('chardev-remove', id='hotplug-chr') + def test_auto_delete(self): + """ + A dynamically-added monitor is configured with 'close-action=delete' + should see itself deleted when the client is closed. + """ + self.set_machine('none') + self.vm.add_args('-nodefaults') + self.vm.launch() + + sock = self._add_monitor(autodelete=True) + + cdevs = [c["label"] for c in self.vm.cmd('query-chardev')] + objs = [o["name"] for o in self.vm.cmd('qom-list', path='/objects')] + assert ('hotplug-chr' in cdevs) + assert ('hotplug-mon' in objs) + + qmp = QEMUMonitorProtocol(sock) + greeting = qmp.connect(negotiate=True) + self.assertIn('QMP', greeting) + + cdevs = [c["label"] for c in self.vm.cmd('query-chardev')] + objs = [o["name"] for o in self.vm.cmd('qom-list', path='/objects')] + assert ('hotplug-chr' in cdevs) + assert ('hotplug-mon' in objs) + + qmp.close() + + for i in range(10): + cdevs = [c["label"] for c in self.vm.cmd('query-chardev')] + if 'hotplug-chr' not in cdevs: + break + # Sleep upto 1/2 second to vary the races + time.sleep(random.random() / 0.5) + + cdevs = [c["label"] for c in self.vm.cmd('query-chardev')] + objs = [o["name"] for o in self.vm.cmd('qom-list', path='/objects')] + assert ('hotplug-chr' not in cdevs) + assert ('hotplug-mon' not in objs) + def test_large_response(self): """ Send a command with a large response (query-qmp-schema) on a -- 2.54.0