From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 97A2760764 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752348AbeFFO21 (ORCPT + 25 others); Wed, 6 Jun 2018 10:28:27 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:56530 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752177AbeFFO2Z (ORCPT ); Wed, 6 Jun 2018 10:28:25 -0400 Subject: Re: [PATCH v5 11/13] KVM: s390: implement mediated device open callback To: pmorel@linux.ibm.com, 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: <1525705912-12815-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1525705912-12815-12-git-send-email-akrowiak@linux.vnet.ibm.com> <98ea7ce2-2539-e2ff-4bb4-297e784d87bd@linux.ibm.com> <7bb480ac-5723-83ff-c797-53c1ab0458c1@linux.vnet.ibm.com> <93cd0f46-a410-51c8-00b9-810c1b3d3ae2@linux.ibm.com> <0f37dc39-7355-19e5-40c9-a02a1ea58c2d@linux.vnet.ibm.com> <736a1346-f81a-7f71-7d13-38729ff78e4f@linux.ibm.com> From: Tony Krowiak Date: Wed, 6 Jun 2018 10:28:17 -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: <736a1346-f81a-7f71-7d13-38729ff78e4f@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: 18060614-0068-0000-0000-000003044104 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009139; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000265; SDB=6.01043027; UDB=6.00534142; IPR=6.00822157; MB=3.00021491; MTD=3.00000008; XFM=3.00000015; UTC=2018-06-06 14:28:23 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18060614-0069-0000-0000-00004496FF2A Message-Id: <8f68183d-8385-8025-1898-23cad604ae94@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-06-06_06:,, 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=8.0.1-1805220000 definitions=main-1806060166 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/05/2018 08:19 AM, Pierre Morel wrote: > On 30/05/2018 16:33, Tony Krowiak wrote: >> On 05/24/2018 05:08 AM, Pierre Morel wrote: >>> On 23/05/2018 16:45, Tony Krowiak wrote: >>>> On 05/16/2018 04:03 AM, Pierre Morel wrote: >>>>> On 07/05/2018 17:11, Tony Krowiak wrote: >>>>>> Implements the open callback on the mediated matrix device. >>>>>> The function registers a group notifier to receive notification >>>>>> of the VFIO_GROUP_NOTIFY_SET_KVM event. When notified, >>>>>> the vfio_ap device driver will get access to the guest's >>>>>> kvm structure. With access to this structure the driver will: >>>>>> >>>>>> 1. Ensure that only one mediated device is opened for the guest >>> >>> You should explain why. >>> >>>>>> >>>>>> 2. Configure access to the AP devices for the guest. >>>>>> >>> ...snip... >>>>>> +void kvm_ap_refcount_inc(struct kvm *kvm) >>>>>> +{ >>>>>> + atomic_inc(&kvm->arch.crypto.aprefs); >>>>>> +} >>>>>> +EXPORT_SYMBOL(kvm_ap_refcount_inc); >>>>>> + >>>>>> +void kvm_ap_refcount_dec(struct kvm *kvm) >>>>>> +{ >>>>>> + atomic_dec(&kvm->arch.crypto.aprefs); >>>>>> +} >>>>>> +EXPORT_SYMBOL(kvm_ap_refcount_dec); >>>>> >>>>> Why are these functions inside kvm-ap ? >>>>> Will anyone use this outer of vfio-ap ? >>>> >>>> As I've stated before, I made the choice to contain all interfaces >>>> that >>>> access KVM in kvm-ap because I don't think it is appropriate for >>>> the device >>>> driver to have to have "knowledge" of the inner workings of KVM. >>>> Why does >>>> it matter whether any entity outside of the vfio_ap device driver >>>> calls >>>> these functions? I could ask a similar question if the interfaces were >>>> contained in vfio-ap; what if another device driver needs access to >>>> these >>>> interfaces? >>> >>> This is very driver specific and only used during initialization. >>> It is not a common property of the cryptographic interface. >>> >>> I really think you should handle this inside the driver. >> >> We are going to have to agree to disagree on this one. Is it not >> possible >> that future drivers - e.g., when full virtualization is implemented - >> will >> require access to KVM? > > I do not think that an access to KVM is required for full virtualization. You may be right, but at this point, there is no guarantee. I stand by my design on this one. > > >