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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 923A2C33C9E for ; Tue, 7 Jan 2020 14:37:02 +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 60E572087F for ; Tue, 7 Jan 2020 14:37:02 +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="fMp8T/SF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 60E572087F 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]:50054 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iopye-0001ym-Nw for qemu-devel@archiver.kernel.org; Tue, 07 Jan 2020 09:37:01 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:40911) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iopx3-0008DC-Dz for qemu-devel@nongnu.org; Tue, 07 Jan 2020 09:35:22 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iopx2-0002E4-7q for qemu-devel@nongnu.org; Tue, 07 Jan 2020 09:35:21 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:53155 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 1iopx2-0002Da-4W for qemu-devel@nongnu.org; Tue, 07 Jan 2020 09:35:20 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1578407719; 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:openpgp:openpgp; bh=XufDugD6uYUlfBGd82PuKlgRYcjdnsQKOQ7nhUL8Mgc=; b=fMp8T/SFONMTS1Hwn4IQhEeL/mABrwdmSHM/CE9Auq9wj8fpXIfisZCeaY8EuMHdwXzWtS InMYHhtchooQtmG2Qv2uMJppFf8bUmZCHhI+tlj838wJLFmxLoSrrb7bThdpxD0z0aiAtF e1sxZXlbRAWbAs7tdZORq/4d4UGmuDE= 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-28-2JdSoVrhPn-gRS9nxHzlnw-1; Tue, 07 Jan 2020 09:35:16 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5102F802CA6; Tue, 7 Jan 2020 14:35:15 +0000 (UTC) Received: from thuth.remote.csb (ovpn-116-116.ams2.redhat.com [10.36.116.116]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6E13E7DB3E; Tue, 7 Jan 2020 14:35:08 +0000 (UTC) Subject: Re: Priority of -accel To: =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= 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> From: Thomas Huth Openpgp: preference=signencrypt Message-ID: Date: Tue, 7 Jan 2020 15:35:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200107142735.GC3368802@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: 2JdSoVrhPn-gRS9nxHzlnw-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 , qemu-block@nongnu.org, Markus Armbruster , Wainer dos Santos Moschetta , qemu-devel@nongnu.org, Paolo Bonzini , Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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 wro= te: >> 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 i= t's >>>>>> really rather common practice to prioritize the last option. So wh= ile >>>>>> 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. Aft= er >>>>> 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... Thus if no "-accel" has been specified, then use kvm/haxm/whpv if possible or TCG otherwise. And if "-accel" has been specified, then only use that accelerator and don't allow a second "-accel" to be specified. Thomas