From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932688AbeCOQA0 (ORCPT ); Thu, 15 Mar 2018 12:00:26 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:57398 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932486AbeCOQAY (ORCPT ); Thu, 15 Mar 2018 12:00:24 -0400 Subject: Re: [PATCH v3 04/14] KVM: s390: device attribute to set AP interpretive execution To: Tony Krowiak , Halil Pasic , 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, berrange@redhat.com, fiuczy@linux.vnet.ibm.com, buendgen@de.ibm.com References: <1521051954-25715-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1521051954-25715-5-git-send-email-akrowiak@linux.vnet.ibm.com> <3afd28d7-57c6-cda6-a436-18da32ef0df3@linux.vnet.ibm.com> From: Pierre Morel Date: Thu, 15 Mar 2018 17:00:03 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <3afd28d7-57c6-cda6-a436-18da32ef0df3@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: 18031516-0008-0000-0000-000004DE4F9C X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18031516-0009-0000-0000-00001E715A69 Message-Id: <1e8a4cfc-1425-b30e-2875-2a5c5d9bcb7c@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-03-15_08:,, 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-1803150176 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15/03/2018 16:23, Tony Krowiak wrote: > On 03/14/2018 05:57 PM, Halil Pasic wrote: >> >> On 03/14/2018 07:25 PM, Tony Krowiak wrote: >>> The VFIO AP device model exploits interpretive execution of AP >>> instructions (APIE) to provide guests passthrough access to AP >>> devices. This patch introduces a new device attribute in the >>> KVM_S390_VM_CRYPTO device attribute group to set APIE from >>> the VFIO AP device defined on the guest. >>> >>> Signed-off-by: Tony Krowiak >>> --- >> [..] >> >>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >>> index a60c45b..bc46b67 100644 >>> --- a/arch/s390/kvm/kvm-s390.c >>> +++ b/arch/s390/kvm/kvm-s390.c >>> @@ -815,6 +815,19 @@ static int kvm_s390_vm_set_crypto(struct kvm >>> *kvm, struct kvm_device_attr *attr) >>> sizeof(kvm->arch.crypto.crycb->dea_wrapping_key_mask)); >>>           VM_EVENT(kvm, 3, "%s", "DISABLE: DEA keywrapping support"); >>>           break; >>> +    case KVM_S390_VM_CRYPTO_INTERPRET_AP: >>> +        if (attr->addr) { >>> +            if (!test_kvm_cpu_feat(kvm, KVM_S390_VM_CPU_FEAT_AP)) >> Unlock mutex before returning? > The mutex is unlocked prior to return at the end of the function. >> >> Maybe flip conditions (don't allow manipulating apie if feature not >> there). >> Clearing the anyways clear apie if feature not there ain't too bad, but >> rejecting the operation appears nicer to me. > I think what you're saying is something like this: > >     if (!test_kvm_cpu_feat(kvm, KVM_S390_VM_CPU_FEAT_AP)) >         return -EOPNOTSUPP; > >     kvm->arch.crypto.apie = (attr->addr) ? 1 : 0; > > I can make arguments for doing this either way, but since the attribute > is will most likely only be set by an AP device in userspace, I suppose > it makes sense to allow setting of the attribute if the AP feature is > installed. It certainly makes sense for the dedicated implementation. >> >>> +                return -EOPNOTSUPP; Obviously Halil is speaking on this return statement. Which returns without unlocking the mutex. -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany