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 66F33C43458 for ; Fri, 3 Jul 2026 13:43:12 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wfeAa-0007KA-9K; Fri, 03 Jul 2026 09:43:04 -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 1wfeAX-0007DZ-1p for qemu-devel@nongnu.org; Fri, 03 Jul 2026 09:43:01 -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 1wfeAT-0003ei-R0 for qemu-devel@nongnu.org; Fri, 03 Jul 2026 09:42:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1783086176; 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=IeQeo6xDXHh3f330cKQqjcWPpGcsCSyhbhx+9Bj9qgs=; b=HEJdadTCK+pNn9zg8XinAsJ5f3PfW7+2rzGuBsR+4o1wIRIjFjTKv/hTivPp6/FQ3t3cTL 7pMtDPyfgX8UaTP/51yZUX2uLjD51A4u98Loa5M8eV9eSY9841MbZCTTKcvfo7RTnUlD0R qseG9Zn3JJdpIVReSmBbx3KEGkUQyww= Received: from mx-prod-mc-01.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-391-YUxoEdIVNO-XfRYA6HF3GA-1; Fri, 03 Jul 2026 09:42:51 -0400 X-MC-Unique: YUxoEdIVNO-XfRYA6HF3GA-1 X-Mimecast-MFC-AGG-ID: YUxoEdIVNO-XfRYA6HF3GA_1783086170 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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E4521196F77B; Fri, 3 Jul 2026 13:42:49 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.44.22.4]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C451636F24; Fri, 3 Jul 2026 13:42:48 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 3F7FE21E6920; Fri, 03 Jul 2026 15:42:46 +0200 (CEST) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Cc: qemu-devel@nongnu.org, Paolo Bonzini , "Dr. David Alan Gilbert" , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Alex =?utf-8?Q?Benn=C3=A9e?= , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Christian Brauner , devel@lists.libvirt.org, Peter Krempa Subject: Re: [PATCH v6 31/34] monitor: add support for auto-deleting monitors upon close In-Reply-To: <20260702160337.1910921-32-berrange@redhat.com> ("Daniel P. =?utf-8?Q?Berrang=C3=A9=22's?= message of "Thu, 2 Jul 2026 17:03:34 +0100") References: <20260702160337.1910921-1-berrange@redhat.com> <20260702160337.1910921-32-berrange@redhat.com> Date: Fri, 03 Jul 2026 15:42:46 +0200 Message-ID: <87jyrcur3d.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 3.6 on 10.30.177.95 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: > 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. I challenged this in review of v5, and you replied with a convincing use case: management application hands a monitor to its client. Would be nice to have in the commit message. Up to you. > 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 > with sending QMP replies. There is still some internal synchronization > needed, however, between the character device event callback and the > bottom-half that runs the delete. There is a chance that an incoming > client connection may arise before the bottom-half runs, which has > to be checked. Once the monitor object is deleted, the event callback > is unregistered from the character device, eliminating any further > races before the character device is fully deleted. > > This is implemented via a new "close-action=3Dnone|delete" property on > the 'monitor-qmp' object. This concept could be extended with further > actions in future, for example: > > * close-action=3Dshutdown - graceful guest shutdown > * close-action=3Dterminate - immediate guest poweroff > * close-action=3Dstop - pause guest CPUs while the monitor is not > connected to any client > > This is left as an exercise for future interested contributors. > > Tested-by: Peter Krempa > Reviewed-by: Marc-Andr=C3=A9 Lureau > Signed-off-by: Daniel P. Berrang=C3=A9 QAPI schema Acked-by: Markus Armbruster