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 X-Spam-Level: X-Spam-Status: No, score=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9E214C3A589 for ; Tue, 20 Aug 2019 21:08:58 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 7264D22DD6 for ; Tue, 20 Aug 2019 21:08:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7264D22DD6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:41682 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i0BNB-0001EP-I4 for qemu-devel@archiver.kernel.org; Tue, 20 Aug 2019 17:08:57 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:53561) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i0BLJ-0008LV-TJ for qemu-devel@nongnu.org; Tue, 20 Aug 2019 17:07:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i0BLI-00081u-03 for qemu-devel@nongnu.org; Tue, 20 Aug 2019 17:07:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53242) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i0BLG-00080V-44 for qemu-devel@nongnu.org; Tue, 20 Aug 2019 17:06:59 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 677608372EE; Tue, 20 Aug 2019 21:06:57 +0000 (UTC) Received: from localhost (ovpn-116-73.gru2.redhat.com [10.97.116.73]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8A48360BF3; Tue, 20 Aug 2019 21:06:54 +0000 (UTC) Date: Tue, 20 Aug 2019 18:06:52 -0300 From: Eduardo Habkost To: Yash Mankad Message-ID: <20190820210652.GL3908@habkost.net> References: <20190815183803.13346-1-ehabkost@redhat.com> <20190815183803.13346-4-ehabkost@redhat.com> <87pnl5sks3.fsf@dusky.pond.sub.org> <20190816074932.GK13569@beluga.usersys.redhat.com> <87h86hpae5.fsf@dusky.pond.sub.org> <20190816174241.GE3908@habkost.net> <75655410-9af9-e463-9471-675299929bde@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <75655410-9af9-e463-9471-675299929bde@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.68]); Tue, 20 Aug 2019 21:06:57 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 3/3] pc: Don't make CPU properties mandatory unless necessary X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Krempa , Like Xu , Erik Skultety , "Michael S. Tsirkin" , qemu-devel@nongnu.org, Markus Armbruster , Igor Mammedov , Paolo Bonzini , Miroslav Rezanina , "Danilo C. L. de Paula" , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Aug 16, 2019 at 05:07:10PM -0400, Yash Mankad wrote: > On 8/16/19 1:42 PM, Eduardo Habkost wrote: > > On Fri, Aug 16, 2019 at 02:22:58PM +0200, Markus Armbruster wrote: > >> Erik Skultety writes: > >> > >>> On Fri, Aug 16, 2019 at 08:10:20AM +0200, Markus Armbruster wrote: > >>>> Eduardo Habkost writes: > >>>> > >>>>> We have this issue reported when using libvirt to hotplug CPUs: > >>>>> https://bugzilla.redhat.com/show_bug.cgi?id=1741451 > >>>>> > >>>>> Basically, libvirt is not copying die-id from > >>>>> query-hotpluggable-cpus, but die-id is now mandatory. > >>>> Uh-oh, "is now mandatory": making an optional property mandatory is an > >>>> incompatible change. When did we do that? Commit hash, please. > >>>> > >>>> [...] > >>>> > >>> I don't even see it as being optional ever - the property wasn't even > >>> recognized before commit 176d2cda0de introduced it as mandatory. > >> Compatibility break. > >> > >> Commit 176d2cda0de is in v4.1.0. If I had learned about it a bit > >> earlier, I would've argued for a last minute fix or a revert. Now we > >> have a regression in the release. > >> > >> Eduardo, I think this fix should go into v4.1.1. Please add cc: > >> qemu-stable. > > I did it in v2. > > > >> How can we best avoid such compatibility breaks to slip in undetected? > >> > >> A static checker would be nice. For vmstate, we have > >> scripts/vmstate-static-checker.py. Not sure it's used. > > I don't think this specific bug would be detected with a static > > checker. "die-id is mandatory" is not something that can be > > extracted by looking at QOM data structures. The new rule was > > being enforced by the hotplug handler callbacks, and the hotplug > > handler call tree is a bit complex (too complex for my taste, but > > I digress). > > > > We could have detected this with a simple CPU hotplug automated > > test case, though. Or with a very simple -device test case like > > the one I have submitted with this patch. > > > > This was detected by libvirt automated test cases. It would be > > nice if this was run during the -rc stage and not only after the > > 4.1.0 release, though. > > > > I don't know details of the test job. Danilo, Mirek, Yash: do > > you know how this bug was detected, and what we could do to run > > the same test jobs in upstream QEMU release candidates? > > This bug was caught by our internal gating tests. > > The libvirt gating tests for the virt module include the > following Avocado-VT test case: > > libvirt_vcpu_plug_unplug.positive_test.vcpu_set.live.vm_operate.save > > This job failed with the error that you can see in the description > of the BZ#1741451 [0]. > > If you think that this would have been caught by a simple hotplug > case, I'd recommend adding a test for hotplug to avocado_qemu. > Otherwise, if you want, I can look into adding this particular > libvirt test case to our QEMU CI efforts. Having a hotplug test case using avocado_qemu would help catch some bugs, but it's not enough if we want to catch integration issues between QEMU and libvirt (like this one). I wouldn't focus just on that particular libvirt test case. I suggest we run a reasonably large set of libvirt test cases against QEMU release candidates as soon as they are tagged. > > Thanks, > Yash > > [0] https://bugzilla.redhat.com/show_bug.cgi?id=1741451#c0 > -- Eduardo