From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751630AbeECQCE (ORCPT ); Thu, 3 May 2018 12:02:04 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:56810 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751141AbeECQCA (ORCPT ); Thu, 3 May 2018 12:02:00 -0400 Subject: Re: [PATCH v4 08/15] KVM: s390: interfaces to (de)configure guest's AP matrix 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, 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: <1523827345-11600-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1523827345-11600-9-git-send-email-akrowiak@linux.vnet.ibm.com> <99f4752a-1358-61e4-bf9e-5672b2d4036f@linux.vnet.ibm.com> <0f47c442-47b8-ee57-d014-5200c59125d7@linux.vnet.ibm.com> <54e4c3ef-0750-981b-7b0e-6b18d1a77c3c@linux.vnet.ibm.com> <7a733e41-3956-6828-9efa-899c9a954c20@linux.vnet.ibm.com> From: Pierre Morel Date: Thu, 3 May 2018 18:01:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <7a733e41-3956-6828-9efa-899c9a954c20@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: 18050316-0020-0000-0000-00000418A114 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18050316-0021-0000-0000-000042ADC3E5 Message-Id: <829b70c7-1648-f1c3-f656-3dca56bb3d8e@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-05-03_07:,, 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 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1805030140 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/05/2018 16:41, Tony Krowiak wrote: > On 05/02/2018 10:57 AM, Pierre Morel wrote: >> On 25/04/2018 18:21, Tony Krowiak wrote: >>> On 04/23/2018 09:46 AM, Pierre Morel wrote: >>>> On 15/04/2018 23:22, Tony Krowiak wrote: >>>>> Provides interfaces to assign AP adapters, usage domains >>>>> and control domains to a KVM guest. ... > The kvm_ap_configure_matrix(kvm, matrix) interface configures the APM, > AQM and ADM in the > guest's CRYCB which implies AP instructions are being interpreted. > There is nothing in SIE > precluding the sharing of AP queues between guests using SIE to > interpret AP instructions, > it is my opinion - along with several others - that this is not > advisable given the > results are not predictable, not to mention the security concerns. If > the protocol to access > queues changes, then we create a different interface. The other option > is to include a flag > on the kvm_ap_configure_matrix(kvm, matrix) interface to indicate > whether sharing is > allowed. I don't like this, because we have no way of knowing if the > caller has taken the > proper care to ensure the VM sharing the queue should be allowed > access. Besides, when > queue sharing is implemented, it is my opinion that we will intercept > the AP instructions > and the matrix will not be configured in the CRYCB. I stick by my > response above. I mean, validating the queue sharing is a mater of the VFIO driver. This code is not needed if the VFIO driver is not used. But it is not very important. > >> >>>>> +static int kvm_ap_matrix_apm_create(struct kvm_ap_matrix *ap_matrix, >>>>> +                    struct ap_config_info *config) >>>>> +{ >>>>> +    int apm_max = (config && config->apxa) ? config->Na + 1 : 16; >>>> >>>> At this moment you already know the format of the crycb. >>> >>> How? >> >> you calculated this in kvm_ap_build_crycbd() which is called from >> kvm_s390_crypto_init() >> itself called from kvm_arch_init_vm(). >> It is when starting the VM. > > This structure is used by the vfio_ap driver to store the mediated > matrix device's matrix > configuration as well as to configure the CRYCB. The mediated device's > matrix is > configured before the guest is started ... it is the means for > configuring the guest's > matrix after all. The bottom line is, this function will be called > long before the > kvm_ap_build_crycbd() function is called. you are right, I was thinking about open, should have take more attention. Sorry. Pierre -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany