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=-2.1 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 3B24BC5DF60 for ; Fri, 8 Nov 2019 12:48:14 +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 0453321D6C for ; Fri, 8 Nov 2019 12:48:14 +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="emwCxC1d" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0453321D6C 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]:53288 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iT3gT-0006lM-1P for qemu-devel@archiver.kernel.org; Fri, 08 Nov 2019 07:48:13 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:46593) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iT3eY-0005KL-3v for qemu-devel@nongnu.org; Fri, 08 Nov 2019 07:46:15 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iT3eV-0003EF-UP for qemu-devel@nongnu.org; Fri, 08 Nov 2019 07:46:13 -0500 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:59539 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 1iT3eV-0003Dt-QF for qemu-devel@nongnu.org; Fri, 08 Nov 2019 07:46:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1573217170; 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=SUo1SvmRW1T9BAStRLEJxmsliYF+9UWqSz6o0sDmKsg=; b=emwCxC1dc8yZmKE04eJUjd6mZBE5jw/DrPMGVDSh/KGgMPh0FgQxzsICed9bYqQk8kQBwP X05TEEhbimtkyfX67AxnpJg+ETfhGtLzXCoGe7XTq6+TUH/WXsvz6Cjdgn/dqG/HqqNHKW uUbyEOQsSmMqoCGf/ZznFSacrSfZ3nI= 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-348-y3ixSvJYPX6lHnb20KvhaA-1; Fri, 08 Nov 2019 07:46:09 -0500 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id A14D58017DD; Fri, 8 Nov 2019 12:46:07 +0000 (UTC) Received: from [10.36.117.63] (ovpn-117-63.ams2.redhat.com [10.36.117.63]) by smtp.corp.redhat.com (Postfix) with ESMTP id 02AC060BE1; Fri, 8 Nov 2019 12:46:01 +0000 (UTC) Subject: Re: [PATCH v1 0/2] s390x/cpumodel: Introduce "best" model variants To: Peter Maydell References: <20191108110714.7475-1-david@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <5dd613c0-6d9e-b943-b64d-7ba1791cbefe@redhat.com> Date: Fri, 8 Nov 2019 13:46:01 +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 2.79 on 10.5.11.12 X-MC-Unique: y3ixSvJYPX6lHnb20KvhaA-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: 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: 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 , Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 08.11.19 12:10, Peter Maydell wrote: > On Fri, 8 Nov 2019 at 11:08, David Hildenbrand wrote: >> >> There was recently a discussion regarding CPU model versions. That conce= pt >> does not fit s390x where we have a lot of feature variability. I >> proposed an alternative approach in [1], which might work for x86 as wel= l >> (but I am not sure if x86 still can or wants to switch to that), and >> requires no real changes in upper layers. >> >> [1] and patch #2 contains more information on the motivation for this. >> >> E.g., specifying/expanding "z14-best" will result in the "best feature >> set possible on this accelerator, hw and, firmware". While a "z13" does >> not work under TCG and some z/VM versions, "z13-best" will work. >=20 > I think other architectures call this concept "max", not "best". > If we can manage some cross-architecture consistency that would > be helpful, but is s390x using 'max' already for something else? We have the "max" model just like other architectures s390 max Enables all features supported by the accelerator=20 in the current host It is basically the "host" model under KVM, and the "qemu" model under=20 TCG (with minor differences for the latter). This series introduces e.g., s390 z900-best IBM zSeries 900 GA1 with best features supported by=20 the accelerator in the current host s390 z14-best IBM z14 GA1 with best features supported by the=20 accelerator in the current host s390 z14ZR1-best IBM z14 Model ZR1 GA1 with best features supported=20 by the accelerator in the current host s390 gen15a-best IBM z15 GA1 with best features supported by the=20 accelerator in the current host s390 gen15b-best IBM 8562 GA1 with best features supported by the=20 accelerator in the current host There is a small but important difference between "max"/"host" and=20 "best". Max really means "all features", including deprecated ones.=20 "best", however, can disable experimental or deprecated features. Or any=20 other features we don't want to be enabled when somebody selects a model=20 manually. On s390x, the feature "csske" is deprecated. New HW still has it, but we=20 want new guests to run without this facility. Dropping it from "max"=20 would affect existing setups. We already changed the default model=20 (e.g., -cpu z13) to disable it with never QEMU machines. E.g., nested virtualization features on some architectures could be a=20 feature set you want to disable, although contained in the "max" model.=20 (e.g., no migration support yet). I am not completely against calling these "max" models instead of "best"=20 models, but I think this makes it clearer that there is indeed a difference= . Maybe, we even want a "-cpu best" that would not map to "-cpu=20 host"/"-cpu max", but to a cleaned up "-cpu host"/"-cpu max" (e.g.,=20 disable deprecated features). Long term, we might even want to change=20 the default when no "-cpu" is specified to "-cpu best" - which should=20 now be possible with the latest QEMU changes to query the default model=20 for a specific QEMU machine. --=20 Thanks, David / dhildenb