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 lists.gnu.org (lists.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 0C1AED3CCAF for ; Thu, 15 Jan 2026 05:58:11 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vgGM7-0006LU-Q6; Thu, 15 Jan 2026 00:57:15 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vgGLu-0006Hq-CB for qemu-devel@nongnu.org; Thu, 15 Jan 2026 00:57:06 -0500 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 1vgGLr-0007pU-TH for qemu-devel@nongnu.org; Thu, 15 Jan 2026 00:57:01 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1768456618; 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=AujIqaltR9/2qrP5D+eeiW4Zw7bpYrGVdmREnV6eSdk=; b=GEflrs/iSQ8XvlLZXsdQfPgSMez0OW7dWcKZb7tPyi6t+Tq6GU33s6bzgI3qDnQYEYvqJo yz95aDOTYrXvo+72SRLh5eWitnZESsmCwRlV6PiFcEEpFWc2WYPvI3DO1GDSbo5ZGwWFG/ f9NAZWdHoLN0+7AJnpYWz0U6stbHzv8= Received: from mx-prod-mc-06.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-693-8Anty3mxOPGA6cZxKgHdOQ-1; Thu, 15 Jan 2026 00:56:54 -0500 X-MC-Unique: 8Anty3mxOPGA6cZxKgHdOQ-1 X-Mimecast-MFC-AGG-ID: 8Anty3mxOPGA6cZxKgHdOQ_1768456613 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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id AEFC0180057E; Thu, 15 Jan 2026 05:56:52 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.32]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A24E730002D8; Thu, 15 Jan 2026 05:56:51 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 3063421E692D; Thu, 15 Jan 2026 06:56:49 +0100 (CET) From: Markus Armbruster To: Peter Xu Cc: qemu-devel@nongnu.org, Juraj Marcin , Fabiano Rosas , Daniel P . =?utf-8?Q?Berrang=C3=A9?= , =?utf-8?B?THVrw6HFoQ==?= Doktor , Juan Quintela , "Dr. David Alan Gilbert" , Zhang Chen , zhanghailiang@xfusion.com, Li Zhijian , Jason Wang Subject: Re: [PATCH 1/3] migration/colo: Deprecate COLO migration framework In-Reply-To: <20260114195659.2543649-2-peterx@redhat.com> (Peter Xu's message of "Wed, 14 Jan 2026 14:56:57 -0500") References: <20260114195659.2543649-1-peterx@redhat.com> <20260114195659.2543649-2-peterx@redhat.com> Date: Thu, 15 Jan 2026 06:56:49 +0100 Message-ID: <875x93zae6.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: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=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 Peter Xu writes: > COLO was broken for QEMU release 10.0/10.1 without anyone noticed. We could arguably drop this right away. I'm not demanding we do, just pointing out. First, COLO is marked 'unstable' in the QAPI schema: * MigrationCapability member x-colo: # @unstable: Members @x-colo and @x-ignore-shared are experimental. * MigrationParameter and MigrationParameters member x-checkpoint-delay: # @unstable: Members @x-checkpoint-delay and # @x-vcpu-dirty-limit-period are experimental. * Command x-colo-lost-heartbeat: # @unstable: This command is experimental. There's more COLO stuff we neglected to mark, e.g. MigrationStatus member @colo, event COLO_EXIT, commands xen-colo-do-checkpoint, query-colo-status. We should clean that up. More on that below. Second, it's been broken for two releases, our deprecation grace period. In my opinion, "broken" is even stronger notice than "deprecated". > One > reason might be that we don't have an unit test for COLO (which we > explicitly require now for any new migration feature). The other reason > should be that there are just no more active COLO users, at least based on > the latest development of QEMU. > > I don't remember seeing anything really active in the past few years in > COLO development. > > Meanwhile, COLO migration framework maintainer (Hailiang Zhang)'s last > email to qemu-devel is in Dec 2021 where the patch proposed an email > change (<20211214075424.6920-1-zhanghailiang@xfusion.com>). > > We've discussed this for a while, see latest discussions here (our though= ts > of deprecating COLO framework might be earlier than that, but still): > > https://lore.kernel.org/r/aQu6bDAA7hnIPg-y@x1.local/ > https://lore.kernel.org/r/20251230-colo_unit_test_multifd-v1-0-f9734bc74c= 71@web.de > > Let's make it partly official and put COLO into deprecation list. If > anyone cares about COLO and is deploying it, please send an email to > qemu-devel to discuss. > > Otherwise, let's try to save some energy for either maintainers or > developers who is looking after QEMU. Let's save the work if we don't even > know what the work is for. > > Cc: Luk=C3=A1=C5=A1 Doktor > Cc: Juan Quintela > Cc: Dr. David Alan Gilbert > Cc: Zhang Chen > Cc: zhanghailiang@xfusion.com > Cc: Li Zhijian > Cc: Jason Wang > Signed-off-by: Peter Xu > --- > docs/about/deprecated.rst | 6 ++++++ > qapi/migration.json | 5 ++--- > migration/options.c | 4 ++++ > 3 files changed, 12 insertions(+), 3 deletions(-) > > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst > index 7abb3dab59..b499b2acb0 100644 > --- a/docs/about/deprecated.rst > +++ b/docs/about/deprecated.rst > @@ -580,3 +580,9 @@ command documentation for details on the ``fdset`` us= age. >=20=20 > The ``zero-blocks`` capability was part of the block migration which > doesn't exist anymore since it was removed in QEMU v9.1. > + > +COLO migration framework (since 11.0) > +''''''''''''''''''''''''''''''''''''' > + > +To be removed with no replacement, as the COLO migration framework doesn= 't > +seem to have any active user for a while. > diff --git a/qapi/migration.json b/qapi/migration.json > index 201dedd982..3c868efe38 100644 > --- a/qapi/migration.json > +++ b/qapi/migration.json > @@ -531,8 +531,7 @@ > # > # @unstable: Members @x-colo and @x-ignore-shared are experimental. > # > -# @deprecated: Member @zero-blocks is deprecated as being part of > -# block migration which was already removed. > +# @deprecated: Member @zero-blocks and @x-colo are deprecated. > # > # Since: 1.2 > ## > @@ -540,7 +539,7 @@ > 'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', > { 'name': 'zero-blocks', 'features': [ 'deprecated' ] }, > 'events', 'postcopy-ram', > - { 'name': 'x-colo', 'features': [ 'unstable' ] }, > + { 'name': 'x-colo', 'features': [ 'unstable', 'deprecated' ] = }, > 'release-ram', > 'return-path', 'pause-before-switchover', 'multifd', > 'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate', Issues / doubts: 1. We delete the text why @zero-blocks is deprecated. Harmless; the next patch drops @zero-blocks entirely. Better: swap the patches. 2. The text for @x-colo is lacking. Suggest something like "Member @x-colo" is deprecated without replacement." 3. Does it make sense to keep x-colo @unstable? 4. Shouldn't we mark *all* the COLO interfaces the same way? > diff --git a/migration/options.c b/migration/options.c > index 9a5a39c886..318850ba94 100644 > --- a/migration/options.c > +++ b/migration/options.c > @@ -580,6 +580,10 @@ bool migrate_caps_check(bool *old_caps, bool *new_ca= ps, Error **errp) > warn_report("zero-blocks capability is deprecated"); > } >=20=20 > + if (new_caps[MIGRATION_CAPABILITY_X_COLO]) { > + warn_report("COLO migration framework is deprecated"); > + } > + > #ifndef CONFIG_REPLICATION > if (new_caps[MIGRATION_CAPABILITY_X_COLO]) { > error_setg(errp, "QEMU compiled without replication module"