From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751995AbeFEMUF (ORCPT ); Tue, 5 Jun 2018 08:20:05 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:40078 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751784AbeFEMUD (ORCPT ); Tue, 5 Jun 2018 08:20:03 -0400 Reply-To: pmorel@linux.ibm.com Subject: Re: [PATCH v5 11/13] KVM: s390: implement mediated device open callback To: 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: <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> From: Pierre Morel Date: Tue, 5 Jun 2018 14:19:53 +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: <0f37dc39-7355-19e5-40c9-a02a1ea58c2d@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 18060512-4275-0000-0000-0000028A5A28 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18060512-4276-0000-0000-000037915E43 Message-Id: <736a1346-f81a-7f71-7d13-38729ff78e4f@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-06-05_05:,, 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-1806050143 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany