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=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 E5F80C433E0 for ; Tue, 16 Jun 2020 10:53:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C042020739 for ; Tue, 16 Jun 2020 10:53:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728450AbgFPKxG (ORCPT ); Tue, 16 Jun 2020 06:53:06 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:51676 "EHLO mx0b-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725775AbgFPKxF (ORCPT ); Tue, 16 Jun 2020 06:53:05 -0400 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 05GAVD7s012471; Tue, 16 Jun 2020 06:52:57 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 31pjnayuk7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 16 Jun 2020 06:52:57 -0400 Received: from m0098421.ppops.net (m0098421.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 05GAVRfu013411; Tue, 16 Jun 2020 06:52:56 -0400 Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 31pjnayujb-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 16 Jun 2020 06:52:56 -0400 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 05GAk93I029967; Tue, 16 Jun 2020 10:52:55 GMT Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by ppma03ams.nl.ibm.com with ESMTP id 31mpe856fq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 16 Jun 2020 10:52:54 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 05GAqps163897766 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 16 Jun 2020 10:52:51 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AC36B4C040; Tue, 16 Jun 2020 10:52:51 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 022204C04A; Tue, 16 Jun 2020 10:52:51 +0000 (GMT) Received: from oc3016276355.ibm.com (unknown [9.145.26.88]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 16 Jun 2020 10:52:50 +0000 (GMT) Subject: Re: [PATCH v2 1/1] s390: virtio: let arch accept devices without IOMMU feature To: Halil Pasic Cc: linux-kernel@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, mst@redhat.com, jasowang@redhat.com, cohuck@redhat.com, kvm@vger.kernel.org, linux-s390@vger.kernel.org, virtualization@lists.linux-foundation.org, thomas.lendacky@amd.com, David Gibson , Ram Pai , Heiko Carstens , Vasily Gorbik References: <1592224764-1258-1-git-send-email-pmorel@linux.ibm.com> <1592224764-1258-2-git-send-email-pmorel@linux.ibm.com> <20200616115202.0285aa08.pasic@linux.ibm.com> From: Pierre Morel Message-ID: Date: Tue, 16 Jun 2020 12:52:50 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200616115202.0285aa08.pasic@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.687 definitions=2020-06-16_04:2020-06-15,2020-06-16 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 phishscore=0 priorityscore=1501 cotscore=-2147483648 malwarescore=0 clxscore=1011 suspectscore=0 lowpriorityscore=0 spamscore=0 mlxlogscore=999 mlxscore=0 impostorscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006160075 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-06-16 11:52, Halil Pasic wrote: > On Mon, 15 Jun 2020 14:39:24 +0200 > Pierre Morel wrote: > > I find the subject (commit short) sub optimal. The 'arch' is already > accepting devices 'without IOMMU feature'. What you are introducing is > the ability to reject. > >> An architecture protecting the guest memory against unauthorized host >> access may want to enforce VIRTIO I/O device protection through the >> use of VIRTIO_F_IOMMU_PLATFORM. >> >> Let's give a chance to the architecture to accept or not devices >> without VIRTIO_F_IOMMU_PLATFORM. >> > > I don't particularly like the commit message. In general, I believe > using access_platform instead of iommu_platform would really benefit us. IOMMU_PLATFORM is used overall in Linux, and I did not find any occurrence for ACCESS_PLATFORM. > >> Signed-off-by: Pierre Morel >> --- >> arch/s390/mm/init.c | 6 ++++++ >> drivers/virtio/virtio.c | 9 +++++++++ >> include/linux/virtio.h | 2 ++ >> 3 files changed, 17 insertions(+) >> >> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c >> index 87b2d024e75a..3f04ad09650f 100644 >> --- a/arch/s390/mm/init.c >> +++ b/arch/s390/mm/init.c >> @@ -46,6 +46,7 @@ >> #include >> #include >> #include >> +#include > > arch/s390/mm/init.c including virtio.h looks a bit strange to me, but > if Heiko and Vasily don't mind, neither do I. Do we have a better place to install the hook? I though that since it is related to memory management and that, since force_dma_unencrypted already is there, it would be a good place. However, kvm-s390 is another candidate. > >> >> pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir); >> >> @@ -162,6 +163,11 @@ bool force_dma_unencrypted(struct device *dev) >> return is_prot_virt_guest(); >> } >> >> +int arch_needs_iommu_platform(struct virtio_device *dev) > > Maybe prefixing the name with virtio_ would help provide the > proper context. The virtio_dev makes it obvious and from the virtio side it should be obvious that the arch is responsible for this. However if nobody has something against I change it. > >> +{ >> + return is_prot_virt_guest(); >> +} >> + >> /* protected virtualization */ >> static void pv_init(void) >> { >> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c >> index a977e32a88f2..30091089bee8 100644 >> --- a/drivers/virtio/virtio.c >> +++ b/drivers/virtio/virtio.c >> @@ -167,6 +167,11 @@ void virtio_add_status(struct virtio_device *dev, unsigned int status) >> } >> EXPORT_SYMBOL_GPL(virtio_add_status); >> >> +int __weak arch_needs_iommu_platform(struct virtio_device *dev) >> +{ >> + return 0; >> +} >> + > > Adding some people that could be interested in overriding this as well > to the cc list. Thanks, > >> int virtio_finalize_features(struct virtio_device *dev) >> { >> int ret = dev->config->finalize_features(dev); >> @@ -179,6 +184,10 @@ int virtio_finalize_features(struct virtio_device *dev) >> if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) >> return 0; >> >> + if (arch_needs_iommu_platform(dev) && >> + !virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) >> + return -EIO; >> + > > Why EIO? Because I/O can not occur correctly? I am open to suggestions. > > Overall, I think it is a good idea to have something that is going to > protect us from this scenario. > It would clearly be a good thing that trusted hypervizors like QEMU forbid this scenario however should we let the door open? Thanks, Pierre -- Pierre Morel IBM Lab Boeblingen