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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 101C8C47257 for ; Thu, 7 May 2020 02:19:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EF3F320747 for ; Thu, 7 May 2020 02:19:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727783AbgEGCTX (ORCPT ); Wed, 6 May 2020 22:19:23 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:37906 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725809AbgEGCTX (ORCPT ); Wed, 6 May 2020 22:19:23 -0400 Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 04722XsG012543; Wed, 6 May 2020 22:19:22 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 30u8t7js3c-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 06 May 2020 22:19:22 -0400 Received: from m0098396.ppops.net (m0098396.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 04722ond014599; Wed, 6 May 2020 22:19:22 -0400 Received: from ppma04wdc.us.ibm.com (1a.90.2fa9.ip4.static.sl-reverse.com [169.47.144.26]) by mx0a-001b2d01.pphosted.com with ESMTP id 30u8t7js2y-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 06 May 2020 22:19:22 -0400 Received: from pps.filterd (ppma04wdc.us.ibm.com [127.0.0.1]) by ppma04wdc.us.ibm.com (8.16.0.27/8.16.0.27) with SMTP id 0472GDLZ029397; Thu, 7 May 2020 02:19:21 GMT Received: from b03cxnp07029.gho.boulder.ibm.com (b03cxnp07029.gho.boulder.ibm.com [9.17.130.16]) by ppma04wdc.us.ibm.com with ESMTP id 30s0g765tb-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 07 May 2020 02:19:21 +0000 Received: from b03ledav005.gho.boulder.ibm.com (b03ledav005.gho.boulder.ibm.com [9.17.130.236]) by b03cxnp07029.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 0472JJT650397670 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 7 May 2020 02:19:19 GMT Received: from b03ledav005.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C9CF8BE05A; Thu, 7 May 2020 02:19:19 +0000 (GMT) Received: from b03ledav005.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8D2DBBE04F; Thu, 7 May 2020 02:19:18 +0000 (GMT) Received: from [9.160.6.78] (unknown [9.160.6.78]) by b03ledav005.gho.boulder.ibm.com (Postfix) with ESMTP; Thu, 7 May 2020 02:19:18 +0000 (GMT) Subject: Re: [PATCH v4 1/1] vfio-ccw: Enable transparent CCW IPL from DASD To: Jared Rossi , Cornelia Huck , Halil Pasic Cc: linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200506212440.31323-1-jrossi@linux.ibm.com> <20200506212440.31323-2-jrossi@linux.ibm.com> From: Eric Farman Message-ID: Date: Wed, 6 May 2020 22:19:17 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200506212440.31323-2-jrossi@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.676 definitions=2020-05-06_09:2020-05-05,2020-05-06 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 adultscore=0 suspectscore=0 bulkscore=0 spamscore=0 mlxlogscore=999 malwarescore=0 priorityscore=1501 phishscore=0 clxscore=1015 impostorscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005070007 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 5/6/20 5:24 PM, Jared Rossi wrote: > Remove the explicit prefetch check when using vfio-ccw devices. > This check does not trigger in practice as all Linux channel programs > are intended to use prefetch. > > It is expected that all ORBs issued by Linux will request prefetch. > Although non-prefetching ORBs are not rejected, they will prefetch > nonetheless. A warning is issued up to once per 5 seconds when a > forced prefetch occurs. > > A non-prefetch ORB does not necessarily result in an error, however > frequent encounters with non-prefetch ORBs indicate that channel > programs are being executed in a way that is inconsistent with what > the guest is requesting. While there is currently no known case of an > error caused by forced prefetch, it is possible in theory that forced > prefetch could result in an error if applied to a channel program that > is dependent on non-prefetch. > > Signed-off-by: Jared Rossi Reviewed-by: Eric Farman > --- > Documentation/s390/vfio-ccw.rst | 6 ++++++ > drivers/s390/cio/vfio_ccw_cp.c | 19 ++++++++++++------- > 2 files changed, 18 insertions(+), 7 deletions(-) > > diff --git a/Documentation/s390/vfio-ccw.rst b/Documentation/s390/vfio-ccw.rst > index fca9c4f5bd9c..23e7d136f8b4 100644 > --- a/Documentation/s390/vfio-ccw.rst > +++ b/Documentation/s390/vfio-ccw.rst > @@ -335,6 +335,12 @@ device. > The current code allows the guest to start channel programs via > START SUBCHANNEL, and to issue HALT SUBCHANNEL and CLEAR SUBCHANNEL. > > +Currently all channel programs are prefetched, regardless of the > +p-bit setting in the ORB. As a result, self modifying channel > +programs are not supported. For this reason, IPL has to be handled as > +a special case by a userspace/guest program; this has been implemented > +in QEMU's s390-ccw bios as of QEMU 4.1. > + > vfio-ccw supports classic (command mode) channel I/O only. Transport > mode (HPF) is not supported. > > diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c > index 3645d1720c4b..f237480c3d43 100644 > --- a/drivers/s390/cio/vfio_ccw_cp.c > +++ b/drivers/s390/cio/vfio_ccw_cp.c > @@ -8,6 +8,7 @@ > * Xiao Feng Ren > */ > > +#include > #include > #include > #include > @@ -625,23 +626,27 @@ static int ccwchain_fetch_one(struct ccwchain *chain, > * the target channel program from @orb->cmd.iova to the new ccwchain(s). > * > * Limitations: > - * 1. Supports only prefetch enabled mode. > - * 2. Supports idal(c64) ccw chaining. > - * 3. Supports 4k idaw. > + * 1. Supports idal(c64) ccw chaining. > + * 2. Supports 4k idaw. > * > * Returns: > * %0 on success and a negative error value on failure. > */ > int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb) > { > + /* custom ratelimit used to avoid flood during guest IPL */ > + static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 1); > int ret; > > /* > - * XXX: > - * Only support prefetch enable mode now. > + * We only support prefetching the channel program. We assume all channel > + * programs executed by supported guests likewise support prefetching. > + * Executing a channel program that does not specify prefetching will > + * typically not cause an error, but a warning is issued to help identify > + * the problem if something does break. > */ > - if (!orb->cmd.pfch) > - return -EOPNOTSUPP; > + if (!orb->cmd.pfch && __ratelimit(&ratelimit_state)) > + dev_warn(mdev, "Prefetching channel program even though prefetch not specified in ORB"); > > INIT_LIST_HEAD(&cp->ccwchain_list); > memcpy(&cp->orb, orb, sizeof(*orb)); >