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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 F2D33C54FCB for ; Fri, 24 Apr 2020 13:03:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DC4AD20736 for ; Fri, 24 Apr 2020 13:03:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727017AbgDXNDE (ORCPT ); Fri, 24 Apr 2020 09:03:04 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:16362 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726489AbgDXNDC (ORCPT ); Fri, 24 Apr 2020 09:03:02 -0400 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 03OCqFF1142293 for ; Fri, 24 Apr 2020 09:03:00 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 30k7rn78xk-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 24 Apr 2020 09:03:00 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 24 Apr 2020 14:02:17 +0100 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 03OD2s6g63832566 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 24 Apr 2020 13:02:54 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 61307A4057; Fri, 24 Apr 2020 13:02:54 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 02D82A4040; Fri, 24 Apr 2020 13:02:54 +0000 (GMT) Received: from oc2783563651 (unknown [9.145.37.140]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 24 Apr 2020 13:02:53 +0000 (GMT) Date: Fri, 24 Apr 2020 15:02:40 +0200 From: Halil Pasic To: Cornelia Huck Cc: Jared Rossi , Eric Farman , linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] vfio-ccw: Enable transparent CCW IPL from DASD In-Reply-To: <20200420141317.4537498f.cohuck@redhat.com> References: <20200417182939.11460-1-jrossi@linux.ibm.com> <20200417182939.11460-2-jrossi@linux.ibm.com> <20200420141317.4537498f.cohuck@redhat.com> Organization: IBM X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 20042413-0008-0000-0000-000003768122 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20042413-0009-0000-0000-00004A9851E9 Message-Id: <20200424150240.6fdede81.pasic@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.676 definitions=2020-04-24_04:2020-04-23,2020-04-24 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 clxscore=1015 mlxscore=0 mlxlogscore=798 adultscore=0 bulkscore=0 impostorscore=0 malwarescore=0 suspectscore=0 spamscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004240097 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, 20 Apr 2020 14:13:17 +0200 Cornelia Huck wrote: > > Remove the explicit prefetch check when using vfio-ccw devices. > > This check is not needed as all Linux channel programs are intended > > to use prefetch and will be executed in the same way regardless. > > Hm... my understanding is that we have the reasonable expectation that > our guests will always issue channel programs that work fine with > prefetch even if the bit is not set in the orb (including CCW IPL, in > the way it is implemented in the s390-ccw QEMU bios), and therefore > this patch is just making things less complicated. AFAIR the problem is not s390-ccw QEMU bios. We could easily fix that. The practical problem is some channel programs generated by zipl that simply fail to set the bit (although they could). That is a perfectly legit thing to do, because the prefetch bit was originally about performance. Sorry I missed your mail, so complained about the same issues. Regards, Halil