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 36BFEC43458 for ; Wed, 1 Jul 2026 07:53:32 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wepke-0000p7-5E; Wed, 01 Jul 2026 03:52:56 -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 1wepkc-0000ov-GP for qemu-devel@nongnu.org; Wed, 01 Jul 2026 03:52:54 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wepka-0007pl-Nj for qemu-devel@nongnu.org; Wed, 01 Jul 2026 03:52:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1782892371; 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=j3hnywmiQL0Bty2fnaG4E5AjlbzFV8f8u4nYjX0ANFM=; b=JcK9pmSp4TU/epjmXAlVDOoDODCxvcvOVzrhR6O15HNM54u7z4+xGUk3Fkfnw8WyWFsdBL GrkEBIEOhQnx3onv/j8vFVihnxMUy78ORMLw+n5wCZTxS9qbNfr1tiJAUGaWepAqc8shar FZm3ukoLBOSC58LkVkpbLX1sHWi96sY= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-499-JVIw_oj9N2qEWY9Ag29QZQ-1; Wed, 01 Jul 2026 03:52:50 -0400 X-MC-Unique: JVIw_oj9N2qEWY9Ag29QZQ-1 X-Mimecast-MFC-AGG-ID: JVIw_oj9N2qEWY9Ag29QZQ_1782892369 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 84A6B1954B3F; Wed, 1 Jul 2026 07:52:48 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.44.22.4]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7DE413000C23; Wed, 1 Jul 2026 07:52:47 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id F3B0721E6920; Wed, 01 Jul 2026 09:52:44 +0200 (CEST) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Cc: qemu-devel@nongnu.org, devel@lists.libvirt.org, =?utf-8?Q?Marc-Andr?= =?utf-8?Q?=C3=A9?= Lureau , Paolo Bonzini , "Dr. David Alan Gilbert" , Alex =?utf-8?Q?Benn=C3=A9e?= , Christian Brauner , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH v5 00/35] monitor: turn QMP and HMP into QOM objects In-Reply-To: <20260624173752.2928717-1-berrange@redhat.com> ("Daniel P. =?utf-8?Q?Berrang=C3=A9=22's?= message of "Wed, 24 Jun 2026 18:37:16 +0100") References: <20260624173752.2928717-1-berrange@redhat.com> Date: Wed, 01 Jul 2026 09:52:44 +0200 Message-ID: <87fr236t9v.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 8 X-Spam_score: 0.8 X-Spam_bar: / X-Spam_report: (0.8 / 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no 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 Daniel P. Berrang=C3=A9 writes: > 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 Possible additional work: change monitor_parse() to build a MonitorOptions instead of a QemuOpts, so it call monitor_new() directly instead of via monitor_new_opts(). Observation, not a demand. > > * QMP gains a concept of "close-action" which makes it > possible to mark a monitor for auto-delete. I'm not quite convinced this is warranted. I'd like to hear more about use cases. Is libvirt going to make use of it? > 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 ~~~ Heh! Fully addressing all review comments before the soft freeze may or may not be possible. Perhaps punting sufficiently harmless changes to a post-freeze fixup series could help. Use your judgement. We could also leave the close-action feature for the next development cycle.