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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 D65E4C33CB1 for ; Wed, 15 Jan 2020 14:03:55 +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 9EF59222C3 for ; Wed, 15 Jan 2020 14:03:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SAMyIiou" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9EF59222C3 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]:54624 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1irjH0-0004tb-Nu for qemu-devel@archiver.kernel.org; Wed, 15 Jan 2020 09:03:54 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:35469) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1irjGC-0004Nh-IL for qemu-devel@nongnu.org; Wed, 15 Jan 2020 09:03:05 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1irjG9-0006kg-Tc for qemu-devel@nongnu.org; Wed, 15 Jan 2020 09:03:02 -0500 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:23777 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1irjG9-0006jV-Ib for qemu-devel@nongnu.org; Wed, 15 Jan 2020 09:03:01 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579096980; 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=yAMf+J+8HdLsShmQyQXks3FV7ejOTYytdp9dloedXTo=; b=SAMyIiouiTkJptP771esYJt2MO9XQt73Y9uMfZqsHzqHIIsKl17jUgsIupSL0YRE/SNe0t 4lfZuNBqhG1KnjICruLS7G+803X4Q0rVJFgxGJcutux7/3VvuRM+ZRl/aXET5HEkqCQQy1 rLTQkKWJ1MYtjnnVy3qwp25O3VUhcaw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-48-gB0RZFZJOOmxOG9AxmjlGQ-1; Wed, 15 Jan 2020 09:02:58 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2557F800D48; Wed, 15 Jan 2020 14:02:57 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-116-131.ams2.redhat.com [10.36.116.131]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 816661CB; Wed, 15 Jan 2020 14:02:49 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 0E4691138600; Wed, 15 Jan 2020 15:02:48 +0100 (CET) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Subject: Re: Making QEMU easier for management tools and applications References: <1EFEF446-AFEA-429F-B6BA-3206A7C41836@redhat.com> <20200108104306.GC5057@dhcp-200-226.str.redhat.com> <97F153BD-FB8A-46C7-90D0-9E894B9E0292@redhat.com> <20200108133842.GE5057@dhcp-200-226.str.redhat.com> <87d0bmchq0.fsf@dusky.pond.sub.org> <1B253197-5592-472A-AA26-E0614A13C91A@redhat.com> <87o8v52hz9.fsf@dusky.pond.sub.org> <8CF8359B-1E52-4F7A-944E-C1C14FEC4F92@redhat.com> <87r200zzje.fsf@dusky.pond.sub.org> <20200115121953.GJ93923@redhat.com> Date: Wed, 15 Jan 2020 15:02:48 +0100 In-Reply-To: <20200115121953.GJ93923@redhat.com> ("Daniel P. =?utf-8?Q?Ber?= =?utf-8?Q?rang=C3=A9=22's?= message of "Wed, 15 Jan 2020 12:19:53 +0000") Message-ID: <874kwwvmuv.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: gB0RZFZJOOmxOG9AxmjlGQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.61 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: Kevin Wolf , Peter Maydell , "Denis V. Lunev" , Stefan Hajnoczi , qemu-devel , Paolo Bonzini , Christophe de Dinechin , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , John Snow , Dominik Csapak Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Daniel P. Berrang=C3=A9 writes: > On Wed, Jan 15, 2020 at 01:15:17PM +0100, Markus Armbruster wrote: >> Christophe de Dinechin writes: >>=20 >> > Thanks a bunch. This clarifies a number of my misconceptions about >> > how this is currently used. Most notably this one: >> > >> >> On 15 Jan 2020, at 10:20, Markus Armbruster wrote= : >> >>=20 >> >>> We don=E2=80=99t want the QAPI to let arbitrary fields of a QOM obje= ct >> >>> be modified, do we? >> >>=20 >> >> We already do: QMP command qom-set. If it breaks your guest, you get= to >> >> keep the pieces. >> > >> > Ouch. I certainly did not expect that. >> > >> > "It is not what you don=E2=80=99t know that kills you, it is what you = know that ain=E2=80=99t so". >>=20 >> Do we have a legitimate use for qom-set right now? Hmm, let's check >> libvirt... aha: >>=20 >> * qemuMonitorJSONSetMemoryStatsPeriod() uses it to control >> virtio-balloon's guest-stats-polling-interval property, in accordance >> with docs/virtio-balloon-stats.txt. >>=20 >> * qemuMonitorJSONSetIOThread() uses it to control iothread's properties >> poll-max-ns, poll-grow, poll-shrink. Their use with -object is >> documented (in qemu-options.hx), their use with qom-set is not. >>=20 >> Oh well. > > Libvirt is of course happy to switch to something else instead of > qom-set for these features if QEMU wants to provide a safer > alternative. Noted. libvirt's use of qom-set is okay. What's not okay is the near-complete lack of QOM documentation, its poor QMP interface, in part due to non-integration with QAPI, and last but not least the lack of QOM leadership leaving it adrift.