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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 821DAC43381 for ; Thu, 28 Feb 2019 13:23:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 47A4420C01 for ; Thu, 28 Feb 2019 13:23:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731224AbfB1NXn (ORCPT ); Thu, 28 Feb 2019 08:23:43 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:59174 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727721AbfB1NXm (ORCPT ); Thu, 28 Feb 2019 08:23:42 -0500 Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x1SDMLif064179 for ; Thu, 28 Feb 2019 08:23:41 -0500 Received: from e06smtp01.uk.ibm.com (e06smtp01.uk.ibm.com [195.75.94.97]) by mx0a-001b2d01.pphosted.com with ESMTP id 2qxfhnjv64-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 28 Feb 2019 08:23:41 -0500 Received: from localhost by e06smtp01.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) Thu, 28 Feb 2019 13:23:36 -0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x1SDNYcA54657112 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 28 Feb 2019 13:23:34 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7BB5FA4051; Thu, 28 Feb 2019 13:23:34 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B02A4A404D; Thu, 28 Feb 2019 13:23:33 +0000 (GMT) Received: from [9.152.224.140] (unknown [9.152.224.140]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 28 Feb 2019 13:23:33 +0000 (GMT) Reply-To: pmorel@linux.ibm.com Subject: Re: [PATCH v4 1/7] s390: ap: kvm: add PQAP interception for AQIC To: Christian Borntraeger , Tony Krowiak Cc: alex.williamson@redhat.com, cohuck@redhat.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, frankja@linux.ibm.com, pasic@linux.ibm.com, david@redhat.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, freude@linux.ibm.com, mimu@linux.ibm.com References: <1550849400-27152-1-git-send-email-pmorel@linux.ibm.com> <1550849400-27152-2-git-send-email-pmorel@linux.ibm.com> <9f1d9241-39b9-adbc-d0e9-cb702e609cbc@linux.ibm.com> <4dc59125-7f96-cba8-651b-382ed8f8bff8@linux.ibm.com> <8526f468-9a4d-68d2-3868-0dad5ce16f46@linux.ibm.com> <6058a017-6404-af3c-62ef-2452214ac97c@de.ibm.com> From: Pierre Morel Date: Thu, 28 Feb 2019 14:23:33 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <6058a017-6404-af3c-62ef-2452214ac97c@de.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: 19022813-4275-0000-0000-000003151985 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19022813-4276-0000-0000-00003823606A Message-Id: <2d52b709-05dd-fa60-658a-36b827cf3041@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-02-28_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=8.0.1-1810050000 definitions=main-1902280092 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/02/2019 10:42, Christian Borntraeger wrote: > > > On 27.02.2019 19:00, Tony Krowiak wrote: >> On 2/27/19 3:09 AM, Pierre Morel wrote: >>> On 26/02/2019 16:47, Tony Krowiak wrote: >>>> On 2/26/19 6:47 AM, Pierre Morel wrote: >>>>> On 25/02/2019 19:36, Tony Krowiak wrote: >>>>>> On 2/22/19 10:29 AM, Pierre Morel wrote: >>>>>>> We prepare the interception of the PQAP/AQIC instruction for >>>>>>> the case the AQIC facility is enabled in the guest. >>>>>>> >>>>>>> We add a callback inside the KVM arch structure for s390 for >>>>>>> a VFIO driver to handle a specific response to the PQAP >>>>>>> instruction with the AQIC command. >>>>>>> >>>>>>> We inject the correct exceptions from inside KVM for the case the >>>>>>> callback is not initialized, which happens when the vfio_ap driver >>>>>>> is not loaded. >>>>>>> >>>>>>> If the callback has been setup we call it. >>>>>>> If not we setup an answer considering that no queue is available >>>>>>> for the guest when no callback has been setup. >>>>>>> >>>>>>> We do consider the responsability of the driver to always initialize >>>>>>> the PQAP callback if it defines queues by initializing the CRYCB for >>>>>>> a guest. >>>>>>> >>>>>>> Signed-off-by: Pierre Morel >>>>> >>>>> ...snip... >>>>> >>>>>>> @@ -592,6 +593,55 @@ static int handle_io_inst(struct kvm_vcpu *vcpu) >>>>>>>       } >>>>>>>   } >>>>>>> +/* >>>>>>> + * handle_pqap: Handling pqap interception >>>>>>> + * @vcpu: the vcpu having issue the pqap instruction >>>>>>> + * >>>>>>> + * We now support PQAP/AQIC instructions and we need to correctly >>>>>>> + * answer the guest even if no dedicated driver's hook is available. >>>>>>> + * >>>>>>> + * The intercepting code calls a dedicated callback for this instruction >>>>>>> + * if a driver did register one in the CRYPTO satellite of the >>>>>>> + * SIE block. >>>>>>> + * >>>>>>> + * For PQAP/AQIC instructions only, verify privilege and specifications. >>>>>>> + * >>>>>>> + * If no callback available, the queues are not available, return this to >>>>>>> + * the caller. >>>>>>> + * Else return the value returned by the callback. >>>>>>> + */ >>>>>>> +static int handle_pqap(struct kvm_vcpu *vcpu) >>>>>>> +{ >>>>>>> +    uint8_t fc; >>>>>>> +    struct ap_queue_status status = {}; >>>>>>> + >>>>>>> +    /* Verify that the AP instruction are available */ >>>>>>> +    if (!ap_instructions_available()) >>>>>>> +        return -EOPNOTSUPP; >>>>>> >>>>>> How can the guest even execute an AP instruction if the AP instructions >>>>>> are not available? If the AP instructions are not available on the host, >>>>>> they will not be available on the guest (i.e., CPU model feature >>>>>> S390_FEAT_AP will not be set). I suppose it doesn't hurt to check this >>>>>> here given QEMU may not be the only client. >>>>>> >>>>>>> +    /* Verify that the guest is allowed to use AP instructions */ >>>>>>> +    if (!(vcpu->arch.sie_block->eca & ECA_APIE)) >>>>>>> +        return -EOPNOTSUPP; >>>>>>> +    /* Verify that the function code is AQIC */ >>>>>>> +    fc = vcpu->run->s.regs.gprs[0] >> 24; >>>>>>> +    if (fc != 0x03) >>>>>>> +        return -EOPNOTSUPP; >>>>>> >>>>>> You must have missed my suggestion to move this to the >>>>>> vcpu->kvm->arch.crypto.pqap_hook(vcpu) in the following responses: >>>>> >>>>> Please consider what happen if the vfio_ap module is not loaded. >>>> >>>> I have considered it and even verified my expectations empirically. If >>>> the vfio_ap module is not loaded, you will not be able to create an mdev device. >>> >>> OK, now please consider that another userland tool, not QEMU uses KVM. >> >> What does that have to do with loading the vfio_ap module? Without the >> vfio_ap module, there will be no AP devices for the guest. What are you >> suggesting here? >> >>> >>>> If you don't have an mdev device, you will not be able to >>>> start a guest with a vfio-ap device. If you start a guest without a >>>> vfio-ap device, but enable AP instructions for the guest, there will be >>>> no AP devices attached to the guest. Without any AP devices attached, >>>> the PQAP(AQIC) instructions will not ever get executed. >>> >>> This is not right. The instruction will be executed, eventually, after decoding. >> >> Please explain why the PQAP(AQIC) instruction will be executed on a >> guest without any devices? Point me to the code in the AP bus where >> PQAP(AQIC) is executed without a queue? > > The host must be prepared to handle malicous and broken guests. So if > a guest does PQAP, we must handle that gracefully (e.g. by injecting an > exception) > >> >>> >>>> Even if for some >>>> unknown reason the PQAP(AQIC) instruction is executed - for some unknown >>>> reason, it will fail with response code 0x01, AP-queue number not valid. >>> >>> No, before accessing the AP-queue the instruction will be decoded and depending on the installed micro-code it will fail with >>> - OPERATION EXCEPTION if the micro-code is not installed >>> - PRIVILEDGE OPERATION if the instruction is issued from userland (programm state) >>> - SPECIFICATION exception if the instruction do not respect the usage specification >>> >>> then it will be interpreted by the microcode and access the queue and only then it will fail with RC 0x01, AP queue not valid. >>> >>> In the case of KVM, we intercept the instruction because it is issued by the guest and we set the AQIC facility on to force interception. >>> >>> KVM do for us all the decode steps I mention here above, if there is or not a pqap hook to be call to simulate the QP queue access. >>> >>> That done, the AP queue virtualisation can be called, this is done by calling the hook. >> >> Okay, let's go back to the genesis of this discussion; namely, my >> suggestion about moving the fc == 0x03 check into the hook code. If >> the vfio_ap module is not loaded, there will be no hook code. In that >> case, the check for the hook will fail and ultimately response code >> 0x01 will be set in the status word (which may not be the right thing >> to do?). You have not stated a single good reason for keeping this >> check, but I'm done with this silly argument. It certainly doesn't >> hurt anything. > > The instruction handler must handle the basic checks for the > instruction itself as outlined above. > > Do we want to allow QEMU to fully emulate everything (the ECA_APIE case being off)? > The we should pass along everything to QEMU, but this is already done with the > ECA_APIE check, correct? > > Do we agree that when we are beyond the ECA_APIE check, that we do not emulate > in QEMU and we have enabled the AP instructions interpretion? > If yes then this has some implication: > > 1. ECA is on and we should only get PQAP interception for specific FC (namely 3). > 2. What we certainly should check is the facility bit of the guest (65) and reject fc==3 > right away with a specification exception. I do not want the hook to mess with > the kvm cpu model. @Pierre would be good to actually check test_kvm_facility(vcpu->kvm, 65)) Currently the check test_kvm_facility(vcpu->kvm, 65) is done in the instruction handler, what do you mean here? Regards, Pierre -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany