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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 2666DC433F5 for ; Mon, 25 Apr 2022 22:06:27 +0000 (UTC) Received: from localhost ([::1]:42192 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nj6qg-0005CM-2K for qemu-devel@archiver.kernel.org; Mon, 25 Apr 2022 18:06:26 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:59670) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nj6or-0004EQ-H9 for qemu-devel@nongnu.org; Mon, 25 Apr 2022 18:04:33 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:36776) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nj6oo-00031U-Ix for qemu-devel@nongnu.org; Mon, 25 Apr 2022 18:04:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1650924270; 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=gsBaHGrNJ9kyiRZniutDwGHGIBab4hTeTCFxe/6fp5k=; b=be6EcsYn7rSC2BOHNWahs5HxP05VGBzb740RqCOFsG3QSqvFTGFeG8jBnOXpc1/eIP/9/D vIUYkkzdOjxJPmQe5U3IWr6g/dKrLcbjulYyevsdeM/6arE/ri58XteZkeB1+VFKP54A2q 8pwm46KjPO/VczWgA1DKiOLmKznJuYE= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-392-PxXEkmpxPLmTHd5EZlyqDw-1; Mon, 25 Apr 2022 18:04:26 -0400 X-MC-Unique: PxXEkmpxPLmTHd5EZlyqDw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 54CEE18E536D; Mon, 25 Apr 2022 22:04:26 +0000 (UTC) Received: from redhat.com (unknown [10.2.16.160]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E62552166B2F; Mon, 25 Apr 2022 22:04:16 +0000 (UTC) Date: Mon, 25 Apr 2022 17:04:14 -0500 From: Eric Blake To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Subject: Re: [PATCH v2] Only advertise aio=io_uring if support is actually available Message-ID: <20220425220414.seud4bu4kojxeajd@redhat.com> References: <20220421165048.12608-1-dmueller@suse.de> <20220421192755.eksb7rfapjsw7qmb@redhat.com> <20220422203046.dd6mc36buja3eusm@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: NeoMutt/20220415-26-c08bba X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Dirk =?utf-8?Q?M=C3=BCller?= , qemu-block@nongnu.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Apr 25, 2022 at 12:19:08PM +0100, Daniel P. Berrangé wrote: > On Fri, Apr 22, 2022 at 03:30:46PM -0500, Eric Blake wrote: > > On Thu, Apr 21, 2022 at 02:27:55PM -0500, Eric Blake wrote: > > > On Thu, Apr 21, 2022 at 06:50:48PM +0200, Dirk Müller wrote: > > > > Change --help output for aio option to only list the aio backend options that > > > > are actually available. io_uring is an optional, linux only backend > > > > option so hide it for cases where it isn't there. > > > > > > As pointed out by Dan, this commit message is not quite accurate. It > > > hides only one of the two conditional options, but 'native' is also a > > > Linux-only optional backend (CONFIG_LINUX_AIO). > > > > Stepping back a bit - we already said that making --help > > machine-parseable is a non-goal, and so the intent of this patch is > > for human readers. But adding an #ifdef ladder to show all 4 possible > > combinations gets hairy; adding another option turns it into 8 > > combinations. Is there a better way > > > > What if we just document ALL strings possible in at least one build > > (no #ifdef ladder in the help text), but add --aio=help as a way to do > > a runtime list of which aio modes are understood by THIS build? It > > would match how we have --device=help for qemu proper, and may even be > > able to reuse some of that framework code (for parsing out when help > > is requested). > > Did you literally mean '--aio=help' ? 'aio' is just an option > for disks, and I don't think we want new top levelk options. So > would have to be '-drive ....,aio=help', or '--blockdev ....aio=help' > the latter gets tricky with nested json syntax though, so not sure > it is nicer. For qemu-nbd, it literally is: --aio=MODE set AIO mode (native, io_uring or threads) so adding --aio=help is already a top-level option there. But for other utilities, you are right that it is a per-device option, and not a top-level thing (qemu-nbd is weird because it exposes exactly one device). -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org