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 D86F6C61DA4 for ; Mon, 6 Feb 2023 14:51:34 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pP2pj-0003ef-DS; Mon, 06 Feb 2023 09:51:03 -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 1pP2pd-0003d2-Tl for qemu-devel@nongnu.org; Mon, 06 Feb 2023 09:51:01 -0500 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 1pP2pc-0004cH-7s for qemu-devel@nongnu.org; Mon, 06 Feb 2023 09:50:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1675695055; h=from:from:reply-to: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=N7fP2miinui2Jt6d6tQALquvb388gwt/ufvkswo0l0I=; b=b4u8ikx0h2tT6TXRTDqQGXal26GRZd9ctJ2k2KGyPjyeRagbdKKR3VfSmJyCQHUYK2uEeQ RUM3nAIQXH5zW7jP46cELrVqf016qov0eKeML0AzsRkCGDHFKCn/VeBsKEkvDZWLcz0wsl XBJ92w9htG78ytQEf9UAWtX5O65vjMM= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-306-24t3nkexP8aISjHQG-iYig-1; Mon, 06 Feb 2023 09:50:52 -0500 X-MC-Unique: 24t3nkexP8aISjHQG-iYig-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id AD362100F911; Mon, 6 Feb 2023 14:50:51 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.62]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 15C31492C3C; Mon, 6 Feb 2023 14:50:47 +0000 (UTC) Date: Mon, 6 Feb 2023 14:50:45 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Thomas Huth Cc: armbru@redhat.com, Michael Roth , Pierre Morel , qemu-s390x@nongnu.org, qemu-devel@nongnu.org, borntraeger@de.ibm.com, pasic@linux.ibm.com, richard.henderson@linaro.org, david@redhat.com, cohuck@redhat.com, mst@redhat.com, pbonzini@redhat.com, kvm@vger.kernel.org, ehabkost@redhat.com, marcel.apfelbaum@gmail.com, eblake@redhat.com, seiden@linux.ibm.com, nrb@linux.ibm.com, nsg@linux.ibm.com, frankja@linux.ibm.com, clg@kaod.org Subject: Re: [PATCH v15 09/11] machine: adding s390 topology to query-cpu-fast Message-ID: References: <20230201132051.126868-1-pmorel@linux.ibm.com> <20230201132051.126868-10-pmorel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 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: -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, SPF_HELO_NONE=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: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Feb 06, 2023 at 02:09:57PM +0100, Thomas Huth wrote: > On 06/02/2023 13.49, Daniel P. Berrangé wrote: > > On Mon, Feb 06, 2023 at 01:41:44PM +0100, Thomas Huth wrote: > > > On 01/02/2023 14.20, Pierre Morel wrote: > > > > S390x provides two more topology containers above the sockets, > > > > books and drawers. > > > > > > > > Let's add these CPU attributes to the QAPI command query-cpu-fast. > > > > > > > > Signed-off-by: Pierre Morel > > > > --- > > > > qapi/machine.json | 13 ++++++++++--- > > > > hw/core/machine-qmp-cmds.c | 2 ++ > > > > 2 files changed, 12 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/qapi/machine.json b/qapi/machine.json > > > > index 3036117059..e36c39e258 100644 > > > > --- a/qapi/machine.json > > > > +++ b/qapi/machine.json > > > > @@ -53,11 +53,18 @@ > > > > # > > > > # Additional information about a virtual S390 CPU > > > > # > > > > -# @cpu-state: the virtual CPU's state > > > > +# @cpu-state: the virtual CPU's state (since 2.12) > > > > +# @dedicated: the virtual CPU's dedication (since 8.0) > > > > +# @polarity: the virtual CPU's polarity (since 8.0) > > > > # > > > > # Since: 2.12 > > > > ## > > > > -{ 'struct': 'CpuInfoS390', 'data': { 'cpu-state': 'CpuS390State' } } > > > > +{ 'struct': 'CpuInfoS390', > > > > + 'data': { 'cpu-state': 'CpuS390State', > > > > + 'dedicated': 'bool', > > > > + 'polarity': 'int' > > > > > > I think it would also be better to mark the new fields as optional and only > > > return them if the guest has the topology enabled, to avoid confusing > > > clients that were written before this change. > > > > FWIW, I would say that the general expectation of QMP clients is that > > they must *always* expect new fields to appear in dicts that are > > returned in QMP replies. We add new fields at will on a frequent basis. > > Did we change our policy here? I slightly remember I've been told > differently in the past ... but I can't recall where this was, it's > certainly been a while. > > So a question to the QAPI maintainers: What's the preferred handling for new > fields nowadays in such situations? I think you're mixing it up with policy for adding new fields to *input* parameters. You can't add a new mandatory field to input params of a command because no existing client will be sending that. Only optional params are viable, without a deprecation cycle. For output parameters such as this case, there's no compatibilty problem. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|