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 78D03ECDFB0 for ; Fri, 13 Jul 2018 10:49:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E5BC20835 for ; Fri, 13 Jul 2018 10:49:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3E5BC20835 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 S1729284AbeGMLDH (ORCPT ); Fri, 13 Jul 2018 07:03:07 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:34212 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727454AbeGMLDH (ORCPT ); Fri, 13 Jul 2018 07:03:07 -0400 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w6DAiL63052463 for ; Fri, 13 Jul 2018 06:48:59 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0b-001b2d01.pphosted.com with ESMTP id 2k6s29v9uw-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 13 Jul 2018 06:48:59 -0400 Received: from localhost by e06smtp03.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, 13 Jul 2018 11:48:52 +0100 Received: from d06av24.portsmouth.uk.ibm.com (d06av24.portsmouth.uk.ibm.com [9.149.105.60]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w6DAmo2429425728 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 13 Jul 2018 10:48:50 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DA97442041; Fri, 13 Jul 2018 13:49:11 +0100 (BST) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2BFA542047; Fri, 13 Jul 2018 13:49:11 +0100 (BST) Received: from oc0155643701.ibm.com (unknown [9.152.224.229]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 13 Jul 2018 13:49:11 +0100 (BST) Subject: Re: [PATCH v6 14/21] s390: vfio-ap: implement mediated device open callback To: Tony Krowiak , 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 References: <1530306683-7270-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1530306683-7270-15-git-send-email-akrowiak@linux.vnet.ibm.com> <9c7ef696-79e5-ef51-be1a-3402a9bb6749@linux.ibm.com> From: Halil Pasic Date: Fri, 13 Jul 2018 12:48:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <9c7ef696-79e5-ef51-be1a-3402a9bb6749@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: 18071310-0012-0000-0000-00000289CCFB X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18071310-0013-0000-0000-000020BB798B Message-Id: <3c9a3de0-4c03-606b-72f1-0afb462844a7@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-07-13_03:,, 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=8.0.1-1806210000 definitions=main-1807130085 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/12/2018 06:03 PM, Tony Krowiak wrote: >>> +static int vfio_ap_mdev_open(struct mdev_device *mdev) >>> +{ >>> +    struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev); >>> +    struct ap_matrix_dev *matrix_dev = >>> +        to_ap_matrix_dev(mdev_parent_dev(mdev)); >>> +    unsigned long events; >>> +    int ret; >>> + >>> +    if (!try_module_get(THIS_MODULE)) >>> +        return -ENODEV; >>> + >>> +    ret = vfio_ap_verify_queues_reserved(matrix_dev, matrix_mdev->name, >>> +                         &matrix_mdev->matrix); >>> +    if (ret) >>> +        goto out_err; >>> + >>> +    matrix_mdev->group_notifier.notifier_call = vfio_ap_mdev_group_notifier; >>> +    events = VFIO_GROUP_NOTIFY_SET_KVM; >>> + >>> +    ret = vfio_register_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY, >>> +                     &events, &matrix_mdev->group_notifier); >>> +    if (ret) >>> +        goto out_err; >>> + >>> +    ret = kvm_ap_validate_crypto_setup(matrix_mdev->kvm); >> >> At this point you assume that your vfio_ap_mdev_group_notifier callback >> was called with VFIO_GROUP_NOTIFY_SET_KVM and that you do have >> matrix_mdev->kvm set up properly. >> >> Based on how callbacks usually work this seems rather strange. It's >> probably cleaner to set up he cyrcb (including all the validation >> that needs to be done immediately before) in the callback >> (vfio_ap_mdev_group_notifier). >> >> If that is not viable I think we need a comment here explaining why is this >> OK (at least). > > This was originally in the callback and moved out, to the best of my recollection, > because the validation at that time was done on the CRYCB and if that validation > failed, there was no way to notify the client (QEMU) that configuration of the > guest's CRYCB failed from the notification callback. This works - at least as far > as I can tell from testing - because the registration of the notifier invokes the > notification callback if KVM has already been set and that appears to be the case. > You are correct, however; we probably shouldn't bank on that given that > I don't think we can guarantee that to be the case 100% of the time. Consequently, > I will move this back into the notification callback and since consistency checking > is now being done on the mdev devices instead of the CRYCB, we don't need KVM at open > time. Sounds good to me. Making the open fail was not a good way to communicate this error condition to userspace anyway. Regards, Halil