From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7C4E1CDB46F for ; Tue, 23 Jun 2026 09:58:31 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wbxtN-0000U5-7z; Tue, 23 Jun 2026 05:58:05 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wbxtL-0000LB-C8 for qemu-devel@nongnu.org; Tue, 23 Jun 2026 05:58:03 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wbxtJ-0003nj-4B for qemu-devel@nongnu.org; Tue, 23 Jun 2026 05:58:03 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1782208680; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Lgb4rSfAZLz/aNf+5eG6humki6zdAtFbfFov9RCL7k0=; b=XSGMFhTKaeeAOXvpVJMx6iqS7SU/nlfnwGV0ixoh0JAnJQ9lYTcIQ3LAVBgudLGDYfyw8N cRPHvtG5EYmUTdQyJFuHi0oNZOMI0FVcEVUSy4YWNrpqyzNRMi47QQGigG2+YVHwcIN9yl yV6kptasLmQRLC0ORnfOpHgHjQ4y7lQ= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-8-gOOyAjBqOy6ljQmtbioh8A-1; Tue, 23 Jun 2026 05:57:55 -0400 X-MC-Unique: gOOyAjBqOy6ljQmtbioh8A-1 X-Mimecast-MFC-AGG-ID: gOOyAjBqOy6ljQmtbioh8A_1782208672 Received: from mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.95]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A6C721801BE8; Tue, 23 Jun 2026 09:57:52 +0000 (UTC) Received: from berrange.com (unknown [10.44.34.133]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id B209DD6E; Tue, 23 Jun 2026 09:57:49 +0000 (UTC) From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: "Dr. David Alan Gilbert" , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Christian Brauner , devel@lists.libvirt.org, Markus Armbruster , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Paolo Bonzini , =?UTF-8?q?Alex=20Benn=C3=A9e?= , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Subject: [PATCH v4 32/35] monitor: add support for auto-deleting monitors upon close Date: Tue, 23 Jun 2026 10:55:48 +0100 Message-ID: <20260623095551.2106712-33-berrange@redhat.com> In-Reply-To: <20260623095551.2106712-1-berrange@redhat.com> References: <20260623095551.2106712-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org 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 --- monitor/monitor-internal.h | 3 + monitor/qmp.c | 68 +++++++++++++++++++ qapi/qom.json | 21 +++++- .../generic/test_monitor_hotplug.py | 55 +++++++++++++-- 4 files changed, 142 insertions(+), 5 deletions(-) diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h index 5522e05464..23829f32f9 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" @@ -178,7 +179,9 @@ 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 5301927f09..f6b7fe65bb 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 +570,38 @@ 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); + object_unref(mon); + 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; + /* Protect against race if a client drops & quickly + * reconnects - we'll have the delete BH scheduled + * so must not honour a new open request + */ + if (mon->delete_pending) { + return; + } + switch (event) { case CHR_EVENT_OPENED: WITH_QEMU_LOCK_GUARD(&mon->parent_obj.mon_lock) { @@ -566,6 +613,7 @@ static void monitor_qmp_event(void *opaque, QEMUChrEvent event) qobject_unref(data); break; case CHR_EVENT_CLOSED: + mon->delete_pending = true; /* * Note: this is only useful when the output of the chardev * backend is still open. For example, when the backend is @@ -577,6 +625,26 @@ 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: + /* + * 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 + * + * Hold an extra ref in case a separate monitor races + * with the BH by processing an expliciti 'object-del' + */ + object_ref(mon); + 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/tests/functional/generic/test_monitor_hotplug.py b/tests/functional/generic/test_monitor_hotplug.py index 55af8a238f..f70aed814f 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 +124,47 @@ 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() + + # Wait upto 10 seconds max for chardev to auto-delete, which + # is hopefully enough for reliability under high load + for i in range(int(10 / 0.2)): + cdevs = [c["label"] for c in self.vm.cmd('query-chardev')] + if 'hotplug-chr' not in cdevs: + break + # Wait a little more then try again + time.sleep(0.2) + + 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