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=-0.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 22B98C004C9 for ; Tue, 7 May 2019 05:08:03 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E2A372087F for ; Tue, 7 May 2019 05:08:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E2A372087F 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 ([127.0.0.1]:39999 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hNsKg-0005Zf-3f for qemu-devel@archiver.kernel.org; Tue, 07 May 2019 01:08:02 -0400 Received: from eggs.gnu.org ([209.51.188.92]:53784) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hNsJq-0005Gz-AS for qemu-devel@nongnu.org; Tue, 07 May 2019 01:07:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hNsJo-0006AY-IT for qemu-devel@nongnu.org; Tue, 07 May 2019 01:07:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35166) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hNsJo-0006A2-Cz for qemu-devel@nongnu.org; Tue, 07 May 2019 01:07:08 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9FDF1C05243E for ; Tue, 7 May 2019 05:07:06 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-116-28.ams2.redhat.com [10.36.116.28]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6292F61496; Tue, 7 May 2019 05:07:06 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id D74331132B35; Tue, 7 May 2019 07:07:04 +0200 (CEST) From: Markus Armbruster To: Eduardo Habkost References: <20190423212246.3542-1-ehabkost@redhat.com> Date: Tue, 07 May 2019 07:07:04 +0200 In-Reply-To: <20190423212246.3542-1-ehabkost@redhat.com> (Eduardo Habkost's message of "Tue, 23 Apr 2019 18:22:43 -0300") Message-ID: <87imumj1jb.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Tue, 07 May 2019 05:07:06 +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 0/3] Export machine type deprecation info through QMP X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mprivozn@redhat.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Eduardo Habkost writes: > This series adds machine type deprecation information to the > output of the `query-machines` QMP command. With this, libvirt > and management software will be able to show this information to > users and/or suggest changes to VM configuration to avoid > deprecated machine types. This overlaps with something I want to try, namely using Kevin's proposed QAPI feature flags for deprecation markings. Let's compare the two. To mark something as deprecated with your patches, you add a @support-status member somewhere, where "somewhere" is related to "something" by "provides information on". Example: MachineInfo (returned by query-machines) provides information on possible values of -machine parameter type. If -machine was QAPIfied, it would provide information on possible values of a QAPI object type's member. The type might be anonymous. The member should be an enum (we currently use 'str' in MachineInfo). Example: say we want to deprecate block driver "vfat", i.e. BlockdevDriver member @vfat. Type BlockdevDriver is used in multiple places; let's ignore all but BlockdevOptions. We need to add @support-status to something that provides information on BlockdevDriver, or maybe on BlockdevOptions. There is no ad hoc query providing information on either of the two, because QAPI/QMP introspection has been sufficient. What now? Can we add deprecation information to (general) QAPI/QMP introspection instead of ad hoc queries? Kevin's proposed QAPI feature flags[*] extend the QAPI language so that struct types can optionally have a list of feature flags, which are strings. Struct types suffice for his immediate needs. I'd like to use feature flags to mark deprecation by tacking a "deprecated" feature onto whatever is deprecated. This obviously needs feature support for everything we want to be able to deprecate: commands, and events, as well as members of enum and object types. Example: to deprecate block driver "vfat", add feature "deprecated" to BlockdevDriver member @vfat. Unlike your patches, this does not require finding a "somewhere" that provides information on "something". You simply tack "deprecated" right onto "something". Your patches provide more information, however: human-readable messages. Food for thought :) [*] Hiding in Subject: [PATCH 0/4] file-posix: Add dynamic-auto-read-only QAPI feature Date: Mon, 8 Apr 2019 16:35:39 +0200 Message-Id: <20190408143543.3982-1-kwolf@redhat.com>