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 54D25ECE560 for ; Mon, 24 Sep 2018 19:46:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EA7CA208D9 for ; Mon, 24 Sep 2018 19:46:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA7CA208D9 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 S1726470AbeIYBuG (ORCPT ); Mon, 24 Sep 2018 21:50:06 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:60400 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726001AbeIYBuF (ORCPT ); Mon, 24 Sep 2018 21:50:05 -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 w8OJi4NS058616 for ; Mon, 24 Sep 2018 15:46:16 -0400 Received: from e35.co.us.ibm.com (e35.co.us.ibm.com [32.97.110.153]) by mx0b-001b2d01.pphosted.com with ESMTP id 2mq48vd9ss-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 24 Sep 2018 15:46:16 -0400 Received: from localhost by e35.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) Mon, 24 Sep 2018 13:46:12 -0600 Received: from b03ledav005.gho.boulder.ibm.com (b03ledav005.gho.boulder.ibm.com [9.17.130.236]) by b03cxnp08028.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w8OJk90j21692564 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 24 Sep 2018 12:46:09 -0700 Received: from b03ledav005.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 762F4BE056; Mon, 24 Sep 2018 13:46:09 -0600 (MDT) Received: from b03ledav005.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B8D31BE058; Mon, 24 Sep 2018 13:46:06 -0600 (MDT) Received: from oc8043147753.ibm.com (unknown [9.85.130.123]) by b03ledav005.gho.boulder.ibm.com (Postfix) with ESMTP; Mon, 24 Sep 2018 13:46:06 -0600 (MDT) Subject: Re: [PATCH v10 11/26] s390: vfio-ap: implement mediated device open callback To: David Hildenbrand , 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> <09a6b9e5-e335-14cf-debd-de0f92dafd5e@redhat.com> <69b5e3d3-5d44-37c0-ca10-720345852134@redhat.com> From: Tony Krowiak Date: Mon, 24 Sep 2018 15:46:06 -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: <69b5e3d3-5d44-37c0-ca10-720345852134@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 18092419-0012-0000-0000-000016BAF85A X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009764; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000267; SDB=6.01093092; UDB=6.00564936; IPR=6.00873129; MB=3.00023486; MTD=3.00000008; XFM=3.00000015; UTC=2018-09-24 19:46:15 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18092419-0013-0000-0000-000054851066 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-09-24_12:,, 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-1809240189 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/24/2018 02:40 PM, David Hildenbrand wrote: > On 24/09/2018 18:07, Tony Krowiak wrote: >> On 09/24/2018 04:40 AM, David Hildenbrand wrote: >>> >>>> /** >>>> - * Verify that the AP instructions are available on the guest. This is >>>> indicated >>>> - * via the KVM_S390_VM_CPU_FEAT_AP CPU model feature. >>>> + * Verify that the AP instructions are being interpreted by firmware >>>> for the >>>> + * guest. This is indicated by the kvm->arch.crypto.apie flag. >>>> */ >>>> static int kvm_ap_validate_crypto_setup(struct kvm *kvm) >>>> { >>>> - if (test_bit_inv(KVM_S390_VM_CPU_FEAT_AP, kvm->arch.cpu_feat)) >>>> + if (kvm->arch.crypto.apie) >>>> return 0; >>> >>> I wonder if this check makes sense, because apie can be toggled during >>> runtime. I guess it would be sufficient to check if the ap control block >>> is available and apie is supported by the HW. >> >> I am not clear about what you are getting at here, but I'll attempt >> to respond. There is no need to check if the AP control block (CRYCB) >> is available as the address is set in the CRYCBD three instructions >> above, even if AP instructions are not available. Regarding whether apie >> is supported by the hardware, the value of vcpu->kvm->arch.crypto.apie >> can not be set unless it is supported by the HW. In the patch (24/26) >> that provides the VM attributes to toggle this value, it can only be >> turned on if the AP instructions are available. I might also note that >> the kvm_ap_validate_crypto_setup() function is called whenever one of >> the VM crypto attributes is changed, so it makes sense that decisions >> made in this function are based on a change to a VM crypto attribute. In >> my first pass at changing this function, I checked >> ap_instructions_available() here, but after considering all of the >> above, it made sense to me to check the apie flag. >> > > I prefer ap_instructions_available(). As I said, kvm->arch.crypto.apie > is a moving target. Looking at this again, I think I responded before my brain shifted from digesting comments about patch 24/26 (enable/disable APIE) to the context for your comment here; namely, the device open callback. My comment above makes no sense in this context. From the perspective of the vfio_ap device driver, there is one requirement that must be met in order to provide pass-through functionality: The AP instructions must be must be interpreted by the HW (i.e., ECA.28 == 1). Checking whether AP instructions are available does not tell us whether they are being interpreted by HW. Checking whether the AP control block (i.e., CRYCB) is available, even when combined with the instruction availability check, does not provide any more insight into the value of ECA.28 becuase the CRYCB will be provided if the MSAX3 facility is installed (STFLE.76) for the guest regardless of whether AP instructions are available or not. There is no doubt that if the AP instructions are not available, then the mdev open callback should fail, but it doesn't tell the whole story. I realize that our CPU model protects against configuring a vfio-ap device for the guest if ap=off, but this function knows nothing about userspace. I can make a similar argument that kvm->arch.crypto.apie will be switched on only if ap=on but again, that is userspace configuration. Having said all of the above, maybe it doesn't really matter whether AP instructions are being interpreted or not. If ECA.28 == 0, then the AP masks may very well be ignored since all AP instructions will be intercepted; so, maybe checking AP instruction availability is all that is needed. I will verify this and if I'm correct, I'll make the change you suggested. >