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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 4F4BDC004C9 for ; Tue, 7 May 2019 16:20:05 +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 243692054F for ; Tue, 7 May 2019 16:20:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 243692054F 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]:49597 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hO2p2-0004r0-7F for qemu-devel@archiver.kernel.org; Tue, 07 May 2019 12:20:04 -0400 Received: from eggs.gnu.org ([209.51.188.92]:44850) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hO2nq-0004Fu-8r for qemu-devel@nongnu.org; Tue, 07 May 2019 12:18:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hO2np-0002rC-6f for qemu-devel@nongnu.org; Tue, 07 May 2019 12:18:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57202) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hO2no-0002qf-RU for qemu-devel@nongnu.org; Tue, 07 May 2019 12:18:49 -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 0624D3E2B0 for ; Tue, 7 May 2019 16:18:48 +0000 (UTC) Received: from localhost (ovpn-116-9.gru2.redhat.com [10.97.116.9]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8D8AB61085; Tue, 7 May 2019 16:18:47 +0000 (UTC) Date: Tue, 7 May 2019 13:18:45 -0300 From: Eduardo Habkost To: Markus Armbruster Message-ID: <20190507161845.GL28722@habkost.net> References: <20190423212246.3542-1-ehabkost@redhat.com> <87imumj1jb.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87imumj1jb.fsf@dusky.pond.sub.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Tue, 07 May 2019 16:18:48 +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" On Tue, May 07, 2019 at 07:07:04AM +0200, Markus Armbruster wrote: > 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). QAPIfying -machine, -cpu, and -device would be wonderful. > > 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 Yes, we can. I think it's a good idea. But: > instead of ad hoc queries? I'm not sure about the "instead of" part. I don't want perfect to be the enemy of done, and I don't want QAPIfication of -machine to be a requirement to start reporting machine type deprecation information. > > 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. It also includes a machine-friendly suggested alternative (which I think is even more important that the human-readable message). We could extend QAPI introspection to return that if necessary, right? > > 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> -- Eduardo