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 65DB0ECE564 for ; Tue, 18 Sep 2018 21:57:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 103512146D for ; Tue, 18 Sep 2018 21:57:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 103512146D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.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 S1730414AbeISDcV (ORCPT ); Tue, 18 Sep 2018 23:32:21 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:41310 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729736AbeISDcU (ORCPT ); Tue, 18 Sep 2018 23:32:20 -0400 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w8ILrvR2118446 for ; Tue, 18 Sep 2018 17:57:43 -0400 Received: from e32.co.us.ibm.com (e32.co.us.ibm.com [32.97.110.150]) by mx0b-001b2d01.pphosted.com with ESMTP id 2mk9bc8r0m-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 18 Sep 2018 17:57:43 -0400 Received: from localhost by e32.co.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) Tue, 18 Sep 2018 15:57:38 -0600 Received: from b03ledav006.gho.boulder.ibm.com (b03ledav006.gho.boulder.ibm.com [9.17.130.237]) by b03cxnp07029.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w8ILvZHp52035634 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 18 Sep 2018 14:57:35 -0700 Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 84661C605D; Tue, 18 Sep 2018 15:57:35 -0600 (MDT) Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8D770C6055; Tue, 18 Sep 2018 15:57:32 -0600 (MDT) Received: from oc8043147753.ibm.com (unknown [9.60.75.213]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTP; Tue, 18 Sep 2018 15:57:32 -0600 (MDT) Subject: Re: [PATCH v10 11/26] s390: vfio-ap: implement mediated device open callback To: Halil Pasic , Tony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: freude@de.ibm.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, borntraeger@de.ibm.com, cohuck@redhat.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: <1536781396-13601-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1536781396-13601-12-git-send-email-akrowiak@linux.vnet.ibm.com> <0ba9647d-76d8-1a6c-bed0-fadd0af496cc@linux.ibm.com> From: Tony Krowiak Date: Tue, 18 Sep 2018 17:57:31 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <0ba9647d-76d8-1a6c-bed0-fadd0af496cc@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 18091821-0004-0000-0000-0000148C5153 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009730; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01090282; UDB=6.00563240; IPR=6.00870303; MB=3.00023372; MTD=3.00000008; XFM=3.00000015; UTC=2018-09-18 21:57:41 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18091821-0005-0000-0000-000088DB4F20 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-09-18_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 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=8.0.1-1807170000 definitions=main-1809180215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/18/2018 01:00 PM, Halil Pasic wrote: > > On 09/12/2018 09:43 PM, Tony Krowiak wrote: >> +/** >> + * vfio_ap_mdev_open_once >> + * >> + * @matrix_mdev: a mediated matrix device >> + * >> + * Return 0 if no other mediated matrix device has been opened for the >> + * KVM guest assigned to @matrix_mdev; otherwise, returns an error. >> + */ >> +static int vfio_ap_mdev_open_once(struct ap_matrix_mdev *matrix_mdev, >> + struct kvm *kvm) >> +{ >> + struct ap_matrix_mdev *m; >> + >> + mutex_lock(&matrix_dev->lock); >> + >> + list_for_each_entry(m, &matrix_dev->mdev_list, node) { >> + if ((m != matrix_mdev) && (m->kvm == kvm)) { >> + mutex_unlock(&matrix_dev->lock); >> + return -EPERM; >> + } >> + } >> + >> + mutex_unlock(&matrix_dev->lock); >> + >> + return 0; >> +} >> + >> +static int vfio_ap_mdev_group_notifier(struct notifier_block *nb, >> + unsigned long action, void *data) >> +{ >> + int ret; >> + struct ap_matrix_mdev *matrix_mdev; >> + >> + if (action != VFIO_GROUP_NOTIFY_SET_KVM) >> + return NOTIFY_OK; >> + >> + matrix_mdev = container_of(nb, struct ap_matrix_mdev, group_notifier); >> + >> + if (!data) { >> + matrix_mdev->kvm = NULL; >> + return NOTIFY_OK; >> + } >> + >> + ret = vfio_ap_mdev_open_once(matrix_mdev, data); > This could be racy. Two threads doing vfio_ap_mdev_group_notifier() > can first get 0 here in a sense that there is no such kvm in the list, > and then both set the very same kvm three lines below. Which would > result in what we are trying to prevent. > > Also vfio_ap_mdev_open_once() does not seem like an appropriate name > any more. If we were to do the matrix_mdev->kvm = kvm in there we could > call it something like vfio_ap_mdev_set_kvm(). I'm moving the matrix-mdev->kvm = kvm inside the mutex lock in vfio_ap_mdev_open_once() ... also renaming it to vfio_ap_mdev_set_kvm(). > >> + if (ret) >> + return NOTIFY_DONE; >> + >> + matrix_mdev->kvm = data; >> + >> + ret = kvm_ap_validate_crypto_setup(matrix_mdev->kvm); >> + if (ret) >> + return ret; >> + >> + vfio_ap_mdev_copy_masks(matrix_mdev); >> + >> + return NOTIFY_OK; >> +}