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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 971B9C432C3 for ; Tue, 19 Nov 2019 10:00:06 +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 5B9CA2075E for ; Tue, 19 Nov 2019 10:00:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="B4iOCqh9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5B9CA2075E 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]:43402 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iX0In-0001dA-Fs for qemu-devel@archiver.kernel.org; Tue, 19 Nov 2019 05:00:05 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:35294) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iX0Hy-0001BL-VQ for qemu-devel@nongnu.org; Tue, 19 Nov 2019 04:59:16 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iX0Hw-0001RZ-Sm for qemu-devel@nongnu.org; Tue, 19 Nov 2019 04:59:14 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:26806 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iX0Hw-0001R2-Nn for qemu-devel@nongnu.org; Tue, 19 Nov 2019 04:59:12 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1574157552; 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=dP3vWiKP9TSPoer7coDxttsww5yKhJDxscwnpTkXDcQ=; b=B4iOCqh99S6hLpqxW6Y1Ztd06vxZzbFNVupY8u9v8O8WL8fSyGwYfpNKWzNB9k4mMQOzNz BpOURaQEYGcjwT5IHg97+1XfdyvwKQnRG8NG5uaLpiOdMMqXAv1ml+3XjSSWXubabt2cQs 0xx5l6GGsuRpqAsYreFry5wC/Lv0M/A= 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-223-Bi_ZxeQ6P6KYk7WNxyLsow-1; Tue, 19 Nov 2019 04:59:09 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 89A7F85B6FE; Tue, 19 Nov 2019 09:59:07 +0000 (UTC) Received: from [10.36.117.126] (ovpn-117-126.ams2.redhat.com [10.36.117.126]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5E27810375D5; Tue, 19 Nov 2019 09:59:00 +0000 (UTC) Subject: Re: [PATCH v1 0/2] s390x/cpumodel: Introduce "best" model variants To: Peter Maydell , Eduardo Habkost References: <5dd613c0-6d9e-b943-b64d-7ba1791cbefe@redhat.com> <20191108191057.GZ3812@habkost.net> <66c64c6d-b7c0-2cb1-2b29-4fdd9b369714@redhat.com> <3aa1d025-20a3-e813-2fe6-35518efedf2f@redhat.com> <20191118184906.GB3812@habkost.net> <20191118220417.GF3812@habkost.net> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Tue, 19 Nov 2019 10:58:59 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-MC-Unique: Bi_ZxeQ6P6KYk7WNxyLsow-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8; format=flowed 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: 207.211.31.120 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: Thomas Huth , =?UTF-8?Q?Daniel_P_=2e_Berrang=c3=a9?= , Janosch Frank , Cornelia Huck , Richard Henderson , QEMU Developers , Markus Armbruster , Halil Pasic , Christian Borntraeger , qemu-s390x , Michael Mueller , Jiri Denemark Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 19.11.19 10:22, Peter Maydell wrote: > On Mon, 18 Nov 2019 at 22:04, Eduardo Habkost wrote= : >> >> On Mon, Nov 18, 2019 at 09:19:55PM +0000, Peter Maydell wrote: >>> Why should it matter whether a feature is enabled >>> or disabled by default in the CPU type? It ought to be probeable >>> by QMP either way (ie there is a difference between >>> "this CPU has this feature switch and it is on by default", >>> "this CPU has this feature switch and it is off by default" >>> and "this CPU does not have this feature switch at all", >>> and presumably libvirt needs to distinguish them). >> >> Its use case is neither "this CPU has this feature switch" or for >> "it is on|off by default". We use it to probe for "this feature >> can be enabled in this host hardware+kernel+QEMU combination". >=20 > OK. Well, the answer to that depends on the name of the CPU, > in general. So you can't use a fake CPU name to try to answer > the question. >=20 >> In other words, in x86 and s390x "max" is just a reserved name >> for the query-cpu-model-expansion command arguments in s390x and >> x86. The fact that it is visible to users can be considered a >> bug, and we can fix that. >=20 > I think 'max' is useful to users, and we've provided it to users, > so removing it again would be a compatibility break. I'm not > entirely sure where we go from here... I agree, right now on s390x "-cpu max" behaves almost like "-cpu=20 qemu"/"-cpu host", but you don't have to care about the accelerator.=20 Removing it might we evil. Removing it is not really an option. >=20 >> If you still don't like how query-cpu-model-expansion works, we >> can also discuss that. But I'm not sure it would be a good use >> of our (and libvirt developers') time. >=20 > I don't hugely care about query-cpu-model-expansion. I > just don't want it to have bad effects on the semantics > of user-facing stuff like x- properties. IMHO, max should really include all features (yes, also the bad=20 x-features on arm :) ) and we should have a way to give users the=20 opportunity to specify "just give me the best model independent of the=20 accelerator" - something like a "best" model, but I don't care about the=20 name. E.g., we could introduce a new model for that purpose and start warning=20 if "-cpu max" is used (and recommend them to use the other model) to run=20 a VM and not simply to query model properties via the qmp interfaces.=20 The users are aware of the model restrictions and can switch. --=20 Thanks, David / dhildenb