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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 10A01C43603 for ; Fri, 20 Dec 2019 21:19:35 +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 D10E32053B for ; Fri, 20 Dec 2019 21:19:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Nc4GkIAn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D10E32053B 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]:33600 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iiPgL-00084c-PL for qemu-devel@archiver.kernel.org; Fri, 20 Dec 2019 16:19:33 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:36584) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iiPfU-00070l-E6 for qemu-devel@nongnu.org; Fri, 20 Dec 2019 16:18:41 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iiPfT-0000Gk-Bo for qemu-devel@nongnu.org; Fri, 20 Dec 2019 16:18:40 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:34623 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iiPfT-0000Ch-6u for qemu-devel@nongnu.org; Fri, 20 Dec 2019 16:18:39 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576876718; 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=l4azdl7XUxdhDKK745rFe5LKT/LLcVGMlTEqAMl93CQ=; b=Nc4GkIAnfdG9ttm9Eq+XmWgt+SCATaeC4ENqxC/i5Z7t1w8XPzcTkMYE0aVMn9I/C35OQr qL5RXsclueetQWMVq2LHAr9ZDSdAG/KyRe2jUQVfQln2Be+S0lCuZwb8jaCHR0s5iOj3Xd 7GLrzgmoj5auxxcjE7jeI0FmHIkXwuo= 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-52-GesS9bwtORyqx_ZfXwISsQ-1; Fri, 20 Dec 2019 16:18:35 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 30DED1883520; Fri, 20 Dec 2019 21:18:34 +0000 (UTC) Received: from [10.3.116.246] (ovpn-116-246.phx2.redhat.com [10.3.116.246]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BC7DC19C68; Fri, 20 Dec 2019 21:18:33 +0000 (UTC) Subject: Re: [PATCH 02/18] fuse: Allow exporting BDSs via FUSE To: Markus Armbruster , Kevin Wolf References: <20191219143818.1646168-1-mreitz@redhat.com> <20191219143818.1646168-3-mreitz@redhat.com> <20191220102656.GD4019@dhcp-200-226.str.redhat.com> <1812e968-1197-523e-7039-caf29e3bbc4b@redhat.com> <20191220112402.GE4019@dhcp-200-226.str.redhat.com> <87pngjgo2h.fsf@dusky.pond.sub.org> <20191220125839.GG4019@dhcp-200-226.str.redhat.com> <877e2rf7sh.fsf@dusky.pond.sub.org> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <931c2067-fe6d-d65d-cc60-d0b20385e84b@redhat.com> Date: Fri, 20 Dec 2019 15:18:33 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <877e2rf7sh.fsf@dusky.pond.sub.org> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: GesS9bwtORyqx_ZfXwISsQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 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: qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 12/20/19 7:25 AM, Markus Armbruster wrote: >> >> I suppose moving a field between a union base and all variants does >> still result in different introspection even though the accepted inputs >> are the same. > > Correct. A common member (whether it's local or from the base) is in > SchemaInfoObject.members[]. Moving it to all the variants moves it to > the variant types' .members[]. > >> Is this kind of movement still allowed unconditionally or >> should we be more careful with something like this? > > QMP's backward compatibility promise does not include "introspection > value won't change". Still, such changes can conceivably confuse > clients. Care is advisable. But it's not a hard "no". And libvirt already correctly handles movements like this (so there are existing clients aware of the potential confusion). -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org