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 45C0AC43381 for ; Thu, 28 Feb 2019 14:12:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 08754214D8 for ; Thu, 28 Feb 2019 14:12:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732562AbfB1OM2 (ORCPT ); Thu, 28 Feb 2019 09:12:28 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:41036 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731320AbfB1OM1 (ORCPT ); Thu, 28 Feb 2019 09:12:27 -0500 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x1SE48DG006555 for ; Thu, 28 Feb 2019 09:12:26 -0500 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0a-001b2d01.pphosted.com with ESMTP id 2qxgk8j6rx-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 28 Feb 2019 09:12:25 -0500 Received: from localhost by e06smtp05.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 14:12:18 -0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x1SECGd517825976 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 28 Feb 2019 14:12:17 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C8CCCA4051; Thu, 28 Feb 2019 14:12:16 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3528BA4053; Thu, 28 Feb 2019 14:12:16 +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 14:12:16 +0000 (GMT) Reply-To: pmorel@linux.ibm.com Subject: Re: [PATCH v4 1/7] s390: ap: kvm: add PQAP interception for AQIC To: Halil Pasic , Christian Borntraeger Cc: Tony Krowiak , 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, 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> <20190228133927.75de6849@oc2783563651> From: Pierre Morel Date: Thu, 28 Feb 2019 15:12:16 +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: <20190228133927.75de6849@oc2783563651> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19022814-0020-0000-0000-0000031C656A X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19022814-0021-0000-0000-0000216DD7E9 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-02-28_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 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902280098 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/02/2019 13:39, Halil Pasic wrote: > On Thu, 28 Feb 2019 10:42:23 +0100 > 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) >> > > Nod. > >>> >>>> >>>>> 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. > > Nod. > >> >> 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? > > Nod. > >> >> 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? > > At least the intention is to not emulate. ECA_APIE is an effective > control though... > >> If yes then this has some implication: >> >> 1. ECA is on and we should only get PQAP interception for specific FC (namely 3). > > Not necessarily true. TAPQ can be intercepted as well (APFT depends > IC.3). But for now we don't care about that. > >> 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)) > > As far as I can tell he already does test_kvm_facility(vcpu->kvm, 65). I > agree we need a spec exception if guest does not have facility 65, but > does have ap instructions. > >> 3. What shall we do when fc == 0x3? We can certainly do the check here OR in the >> hook. As long as we have only fc==3 this does not matter. >> > > I guess Tony's point is that we may have fc == 0 that is TAPQ in the > APFT flavor. IMHO we don't need to care about that at the moment. > >> Correct? > > IMHO mostly. > > I also doing the facility checks in kvm is easier, and I think this is > something we can change later if needed without any major trouble. > > There are a couple of things I would do differently than Pierre does: > 1) Do the PGM_PRIVILEGED_OP before the fc == 3 check. Idea was not to modify existing behavior for fc != 3 Also Christian already proposed to handle all FC codes. So in this idea, this must be done as you say. > > 2) Do the test_kvm_facility(vcpu->kvm, 65) check in the context of fc == > 3. I.e. decide if this hook is about pqap or just about pqap aqic and > make the code convey that decision to its reader. > > 3) I would most probably test if the queue is available by looking at the > masks in CRYCB here. If not AP_RESPONSE_Q_NOT_AVAIL is what we need. This I do not agree with, it is typically the responsibility of the part in charge of the virtualization to do this, also the vfio_driver. > > 4) If we have APIE and queues authorized by the CRYCB (i.e. we have a > vfio_ap module loaded an an mdev associated with the kvm) the callback > not set (!(vcpu->kvm->arch.crypto.pqap_hook)) is a BUG! I do not agree with this either, the maintainers ;) will not allow this. > In that case > lying that the queue is not available does not seem right. BTW this is > something Pierre changed since the last version quietly (I can't recall > a mention in the change log or somebody asking for this). If we want to > be very pedantic about this bug scenario our best bet is probably > response code 6. RC 06 means "Invalid address of AP-queue notification byte" So you must have think about another code or I do not understand at all what you mean. Regards, Pierre -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany