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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 B8649C43381 for ; Fri, 29 Mar 2019 13:23:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F00620700 for ; Fri, 29 Mar 2019 13:23:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729641AbfC2NX2 (ORCPT ); Fri, 29 Mar 2019 09:23:28 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:46876 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729524AbfC2NX1 (ORCPT ); Fri, 29 Mar 2019 09:23:27 -0400 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x2TDMtfN040946 for ; Fri, 29 Mar 2019 09:23:26 -0400 Received: from e13.ny.us.ibm.com (e13.ny.us.ibm.com [129.33.205.203]) by mx0b-001b2d01.pphosted.com with ESMTP id 2rhk24v2sn-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 29 Mar 2019 09:23:03 -0400 Received: from localhost by e13.ny.us.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, 29 Mar 2019 13:14:52 -0000 Received: from b01ledav001.gho.pok.ibm.com (b01ledav001.gho.pok.ibm.com [9.57.199.106]) by b01cxnp23032.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x2TDEnOR11665484 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 29 Mar 2019 13:14:49 GMT Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 29F1E28059; Fri, 29 Mar 2019 13:14:49 +0000 (GMT) Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7BCA528058; Fri, 29 Mar 2019 13:14:48 +0000 (GMT) Received: from [9.80.196.185] (unknown [9.80.196.185]) by b01ledav001.gho.pok.ibm.com (Postfix) with ESMTP; Fri, 29 Mar 2019 13:14:48 +0000 (GMT) Subject: Re: [PATCH v6 4/7] vfio: ap: register IOMMU VFIO notifier To: pmorel@linux.ibm.com, borntraeger@de.ibm.com Cc: alex.williamson@redhat.com, cohuck@redhat.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, frankja@linux.ibm.com, pasic@linux.ibm.com, david@redhat.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, freude@linux.ibm.com, mimu@linux.ibm.com References: <1553265828-27823-1-git-send-email-pmorel@linux.ibm.com> <1553265828-27823-5-git-send-email-pmorel@linux.ibm.com> <1731fb82-7877-9018-d12e-fd0e2406ac19@linux.ibm.com> <7a4bf9f1-5046-5838-a50d-8402782c880f@linux.ibm.com> From: Tony Krowiak Date: Fri, 29 Mar 2019 09:14:48 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <7a4bf9f1-5046-5838-a50d-8402782c880f@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19032913-0064-0000-0000-000003C27663 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010834; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000283; SDB=6.01181366; UDB=6.00618317; IPR=6.00962086; MB=3.00026208; MTD=3.00000008; XFM=3.00000015; UTC=2019-03-29 13:14:55 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19032913-0065-0000-0000-00003CE06C02 Message-Id: <9af30e31-e4d8-160e-d7a1-8365185d2933@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-03-29_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903290097 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/29/19 5:31 AM, Pierre Morel wrote: > On 28/03/2019 21:46, Tony Krowiak wrote: >> On 3/22/19 10:43 AM, Pierre Morel wrote: >>> To be able to use the VFIO interface to facilitate the >>> mediated device memory pinning/unpinning we need to register >>> a notifier for IOMMU. >>> >>> While we will start to pin one guest page for the interrupt indicator >>> byte, this is still ok with ballooning as this page will never be >>> used by the guest virtio-balloon driver. >>> So the pinned page will never be freed. And even a broken guest does >>> so, that would not impact the host as the original page is still >>> in control by vfio. >> >> I apologize, but I do not understand what you are saying in the second >> sentence of the paragraph above. Why will the pinned page never be freed? > Because it is in use by the guest's kernel as a notification information > byte for the original PQAP AQIC. Your comment says the pinned page will never be free, doesn't it get freed when the guest is terminated? > >  I understand that the pinned page is under the control of vfio >> until it is freed, but have no idea what you mean by "and even a broken >> guest does so"? A broken guest does what? Can you please reword this so >> it makes more sense? > > A broken guest could free the page used for the NIB. What is obviously > wrong. Then why not simply say a pinned page is under the control of the vfio driver, so if a broken (malicious?) guest frees the page, it will not impact the host or something to that effect. > >> >>> >>> Signed-off-by: Pierre Morel >>> Reviewed-by: Cornelia Huck >>> --- >>>   drivers/s390/crypto/vfio_ap_ops.c     | 38 >>> +++++++++++++++++++++++++++++++++++ >>>   drivers/s390/crypto/vfio_ap_private.h |  2 ++ >>>   2 files changed, 40 insertions(+) >>> >>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c >>> b/drivers/s390/crypto/vfio_ap_ops.c >>> index bdb36e0..3478499 100644 >>> --- a/drivers/s390/crypto/vfio_ap_ops.c >>> +++ b/drivers/s390/crypto/vfio_ap_ops.c >>> @@ -787,6 +787,35 @@ static const struct attribute_group >>> *vfio_ap_mdev_attr_groups[] = { >>>       NULL >>>   }; >>> +/** >>> + * vfio_ap_mdev_iommu_notifier: IOMMU notifier callback >>> + * >>> + * @nb: The notifier block >>> + * @action: Action to be taken >>> + * @data: data associated with the request >>> + * >>> + * For an UNMAP request, unpin the guest IOVA (the NIB guest address we >>> + * pinned before). Other requests are ignored. >>> + * >>> + */ >>> +static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb, >>> +                       unsigned long action, void *data) >>> +{ >>> +    struct ap_matrix_mdev *matrix_mdev; >>> + >>> +    matrix_mdev = container_of(nb, struct ap_matrix_mdev, >>> iommu_notifier); >>> + >> >> I don't understand why we registered this notifier. I may be wrong, but >> AFAIU, this notifier will be invoked only when the VFIO_IOMMU_UNMAP_DMA >> ioctl is called from userspace. I did an experiment and inserted some >> printf's to see if this ever gets called and verified it does not. Maybe >> you have a good reason of which I'm not aware. Can you enlighten me >> here? > > The vfio_iommu_type1 pin page requires a notifier. > > Regards, > Pierre >