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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 CBA27ECE562 for ; Mon, 17 Sep 2018 07:57:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6DCC0214C2 for ; Mon, 17 Sep 2018 07:57:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6DCC0214C2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727460AbeIQNX3 (ORCPT ); Mon, 17 Sep 2018 09:23:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58668 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726652AbeIQNX3 (ORCPT ); Mon, 17 Sep 2018 09:23:29 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 46F7086664; Mon, 17 Sep 2018 07:57:15 +0000 (UTC) Received: from [10.36.117.44] (ovpn-117-44.ams2.redhat.com [10.36.117.44]) by smtp.corp.redhat.com (Postfix) with ESMTP id 053A817A66; Mon, 17 Sep 2018 07:57:06 +0000 (UTC) Subject: Re: [PATCH v9 21/22] KVM: s390: CPU model support for AP virtualization To: Tony Krowiak , Cornelia Huck Cc: Tony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, freude@de.ibm.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, borntraeger@de.ibm.com, kwankhede@nvidia.com, bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com, alex.williamson@redhat.com, pmorel@linux.vnet.ibm.com, alifm@linux.vnet.ibm.com, mjrosato@linux.vnet.ibm.com, jjherne@linux.vnet.ibm.com, thuth@redhat.com, pasic@linux.vnet.ibm.com, berrange@redhat.com, fiuczy@linux.vnet.ibm.com, buendgen@de.ibm.com, frankja@linux.ibm.com References: <1534196899-16987-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1534196899-16987-22-git-send-email-akrowiak@linux.vnet.ibm.com> <2c2c4859-ed3e-a492-dd59-78529c7768b2@redhat.com> <8f3f3f41-a052-1975-69e2-49e1a662ecab@linux.ibm.com> <38b87fc4-9344-70d8-4602-bf8e114769ef@redhat.com> <20180823102447.05430368.cohuck@redhat.com> <1e0fc615-101c-7b9d-6dd1-de9a43fae734@linux.ibm.com> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <1e0fc615-101c-7b9d-6dd1-de9a43fae734@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Mon, 17 Sep 2018 07:57:15 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 12.09.18 um 19:42 schrieb Tony Krowiak: > On 08/23/2018 04:24 AM, Cornelia Huck wrote: >> On Thu, 23 Aug 2018 09:48:48 +0200 >> David Hildenbrand wrote: >> >>>> Migration of AP devices is not supported by this patch series, so this >>>> should >>>> not be an issue. >>> Might not be a problem now, but could be later. As I said in a different >>> reply, the CPU model in QEMU does not care about KVM. >>> >>> I want the QEMU CPU model and the KVM interfaces to be clean and future >>> proof. That's why my opinion is to handle PQAP(QCI) just like all the >>> other "feature blocks" we already have. >> +1 to that sentiment. >> >> It's better to try to get this correct now than having to hack around >> should we want to implement things in the future. > > Just so we're on the same page here as far as what to expect for v10 of > this patch series, let me summarize the the very long series of private > exchanges as well as this thread: > > * The APXA facility indicated by a bit returned in the response to the > PQAP(QCI) function indicates only whether the APXA facility is available > on one or more APs installed on the system. > * The only way to change the bit returned from PQAP(QCI) is to intercept the > instruction and emulate it, so it makes no sense for passthrough devices. > * The AP(s) with APXA installed may not necessarily even be in the > configuration. > * The only way to determine whether APXA is installed in a given AP is to > query it using the PQAP(TAPQ) instruction. > > It was decided that APXA is better modeled as device configuration. If > and when > emulation is implemented, APXA can be configured for any AP devices assigned > to a guest. Since AP instructions will be intercepted when emulating AP, > the PQAP(QCI) instruction can return the APXA bit according to whether any > AP is configured with APXA installed. That matches the real architecture > much > more closely. So, the bottom line is that we will not introduce a new > CPU model > feature for APXA in v10 of this series. Yes, that sounds sane to me. In addition, all other QCI indicated "features/facilitites" are handled on a per-device basis and not on a CPU-model basis. -- Thanks, David / dhildenb