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 5E02CC33CAD for ; Mon, 13 Jan 2020 14:39:57 +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 2976F20678 for ; Mon, 13 Jan 2020 14:39:57 +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="BfFOLNP4" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2976F20678 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]:51254 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ir0sm-0003oR-CG for qemu-devel@archiver.kernel.org; Mon, 13 Jan 2020 09:39:56 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:41592) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ir0s8-0003Jr-Fm for qemu-devel@nongnu.org; Mon, 13 Jan 2020 09:39:17 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ir0s6-0001Pj-MF for qemu-devel@nongnu.org; Mon, 13 Jan 2020 09:39:15 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:35330 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 1ir0s6-0001OT-J8 for qemu-devel@nongnu.org; Mon, 13 Jan 2020 09:39:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1578926354; 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=7OXKzFO2f/u4qusUYSwUTZfUyD3qRQFFfVRLHrTpJUc=; b=BfFOLNP42zCV97STbTfR+rJKM+jMaiQ+Ln/ou4yJ7FCgaib3z66uhF8Y+VSi4Bw056npfc 9cSXwJhbrVAoC8qX4bSBZxMiPo9I8U7gxOb2VHJ/sCxkuyYtlRkTQ3HQC8KeVnhaqa4Ttu wMSdywH/wYGmGgMMxx0VZKqDExGNtEA= 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-306-UohzXGCIOO6ZiviFfSFwmQ-1; Mon, 13 Jan 2020 09:39:11 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 16689805455; Mon, 13 Jan 2020 14:39:10 +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 8FC1E5DA7B; Mon, 13 Jan 2020 14:39:03 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 0C85C1138600; Mon, 13 Jan 2020 15:39:02 +0100 (CET) From: Markus Armbruster To: Thomas Huth Subject: Re: Priority of -accel References: <20200106130951.29873-1-philmd@redhat.com> <12334054-4ae7-e580-9727-2d322bfa2bda@redhat.com> <58eb34db-7d32-8b0e-d9ef-98648209486b@redhat.com> <656169fc-1abe-b521-20a3-e7041739b914@redhat.com> <20200107125451.GL3368802@redhat.com> <3241dff4-6223-404f-55d4-846991763046@redhat.com> <2ae2dee3-cd16-a247-971b-4b3482e596a5@redhat.com> <20200107142735.GC3368802@redhat.com> Date: Mon, 13 Jan 2020 15:39:02 +0100 In-Reply-To: (Thomas Huth's message of "Tue, 7 Jan 2020 15:35:06 +0100") Message-ID: <871rs3zaih.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 10.5.11.14 X-MC-Unique: UohzXGCIOO6ZiviFfSFwmQ-1 X-Mimecast-Spam-Score: 0 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 , "Daniel P. =?utf-8?Q?Berrang=C3=A9?=" , qemu-block@nongnu.org, qemu-devel@nongnu.org, Wainer dos Santos Moschetta , Max Reitz , Paolo Bonzini , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Thomas Huth writes: > On 07/01/2020 15.27, Daniel P. Berrang=C3=A9 wrote: >> On Tue, Jan 07, 2020 at 03:20:40PM +0100, Philippe Mathieu-Daud=C3=A9 wr= ote: >>> On 1/7/20 3:14 PM, Thomas Huth wrote: >>>> On 07/01/2020 13.54, Daniel P. Berrang=C3=A9 wrote: >>>>> On Tue, Jan 07, 2020 at 01:23:18PM +0100, Paolo Bonzini wrote: >>>>>> On 07/01/20 13:18, Thomas Huth wrote: >>>>>>> I don't think we need a separate priority parameter here. But IMHO = it's >>>>>>> really rather common practice to prioritize the last option. So w= hile >>>>>>> it might be more "self-explanatory" to a CLI newbie if the first >>>>>>> occurrence got the highest priority, it might be rather confusing >>>>>>> instead for a CLI veteran...? >>>>>> >>>>>> Prioritising the last certainly makes sense for a choose-one-only >>>>>> option, but I'm not sure it's the same for a choose-best option. Af= ter >>>>>> all it was -machine accel=3Dkvm:tcg, not -machine accel=3Dtcg:kvm... >>>>> >>>>> IIUC, the main use case for specifying multiple accelerators is >>>>> so that lazy invokations can ask for a hardware virt, but then get >>>>> fallback to TCG if not available. For things that should be platform >>>>> portabile, there's more than just kvm to consider though, as we have >>>>> many accelerators. Listing all possible accelerators is kind of >>>>> crazy though no matter what the syntax is. >>>>> >>>>> How about taking a completely different approach, inspired by the >>>>> -cpu arg and implement: >>>>> >>>>> -machine accel=3Dbest >>>> >>>> Something like that sounds like the best solution to me, but I'd maybe >>>> rather not call it "best", since the definition of "best" might depend >>>> on your use-case (e.g. do you want to use a CPU close to the host or >>>> something different which might be better emulated by TCG?). >>>> >>>> What about "-accel any" or "-accel fastest" or something similar? >>> >>> 'any' is a russian roulette, you don't want it to return 'qtest' ;) >>=20 >> We could make it return "qtest" only on April 1st ;-P > > ... or we finally dare to let QEMU chose the "best" accelerator by > default if no "-accel" option has been specified... Changing a default that has ceased to make sense a decade ago? Are you out of your mind? ;-P [...]