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Tue, 15 Jun 2021 08:55:13 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.171.85.205]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id F0C2852052; Tue, 15 Jun 2021 08:55:12 +0000 (GMT) Subject: Re: [PATCH 3/3] s390/vfio-ap: r/w lock for PQAP interception handler function pointer To: Tony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Cc: cohuck@redhat.com, pasic@linux.vnet.ibm.com, jjherne@linux.ibm.com, jgg@nvidia.com, alex.williamson@redhat.com, kwankhede@nvidia.com, frankja@linux.ibm.com, david@redhat.com, imbrenda@linux.ibm.com, hca@linux.ibm.com References: <20210609224634.575156-1-akrowiak@linux.ibm.com> <20210609224634.575156-4-akrowiak@linux.ibm.com> From: Christian Borntraeger Message-ID: Date: Tue, 15 Jun 2021 10:55:12 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <20210609224634.575156-4-akrowiak@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: hCG9fKVZ65E2cOJfmS09OYnKEqLytMjA X-Proofpoint-GUID: SmhyFqlu7n1lJQoQF2QQUzkfKqQ8Nct_ X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-15_04:2021-06-14,2021-06-15 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 malwarescore=0 priorityscore=1501 impostorscore=0 mlxlogscore=999 adultscore=0 lowpriorityscore=0 clxscore=1015 spamscore=0 suspectscore=0 phishscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106150051 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10.06.21 00:46, Tony Krowiak wrote: > The function pointer to the interception handler for the PQAP instruction > can get changed during the interception process. Let's add a > semaphore to struct kvm_s390_crypto to control read/write access to the > function pointer contained therein. > > The semaphore must be locked for write access by the vfio_ap device driver > when notified that the KVM pointer has been set or cleared. It must be > locked for read access by the interception framework when the PQAP > instruction is intercepted. > > Signed-off-by: Tony Krowiak Given that patch 2 is still under discussion. Can this patch go without patch 2? > --- > arch/s390/include/asm/kvm_host.h | 6 +++--- > arch/s390/kvm/kvm-s390.c | 1 + > arch/s390/kvm/priv.c | 6 +++--- > drivers/s390/crypto/vfio_ap_ops.c | 14 ++++++++++---- > drivers/s390/crypto/vfio_ap_private.h | 2 +- > 5 files changed, 18 insertions(+), 11 deletions(-) > > diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h > index 8925f3969478..58edaa3f9602 100644 > --- a/arch/s390/include/asm/kvm_host.h > +++ b/arch/s390/include/asm/kvm_host.h > @@ -803,14 +803,14 @@ struct kvm_s390_cpu_model { > unsigned short ibc; > }; > > -struct kvm_s390_module_hook { > +struct kvm_s390_crypto_hook { > int (*hook)(struct kvm_vcpu *vcpu); > - struct module *owner; > }; > > struct kvm_s390_crypto { > struct kvm_s390_crypto_cb *crycb; > - struct kvm_s390_module_hook *pqap_hook; > + struct rw_semaphore pqap_hook_rwsem; > + struct kvm_s390_crypto_hook *pqap_hook; > __u32 crycbd; > __u8 aes_kw; > __u8 dea_kw; > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index 1296fc10f80c..418d910df569 100644 > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c > @@ -2606,6 +2606,7 @@ static void kvm_s390_crypto_init(struct kvm *kvm) > { > kvm->arch.crypto.crycb = &kvm->arch.sie_page2->crycb; > kvm_s390_set_crycb_format(kvm); > + init_rwsem(&kvm->arch.crypto.pqap_hook_rwsem); > > if (!test_kvm_facility(kvm, 76)) > return; > diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c > index 9928f785c677..bbbd84ffe239 100644 > --- a/arch/s390/kvm/priv.c > +++ b/arch/s390/kvm/priv.c > @@ -657,15 +657,15 @@ static int handle_pqap(struct kvm_vcpu *vcpu) > * Verify that the hook callback is registered, lock the owner > * and call the hook. > */ > + down_read(&vcpu->kvm->arch.crypto.pqap_hook_rwsem); > if (vcpu->kvm->arch.crypto.pqap_hook) { > - if (!try_module_get(vcpu->kvm->arch.crypto.pqap_hook->owner)) > - return -EOPNOTSUPP; > ret = vcpu->kvm->arch.crypto.pqap_hook->hook(vcpu); > - module_put(vcpu->kvm->arch.crypto.pqap_hook->owner); > if (!ret && vcpu->run->s.regs.gprs[1] & 0x00ff0000) > kvm_s390_set_psw_cc(vcpu, 3); > + up_read(&vcpu->kvm->arch.crypto.pqap_hook_rwsem); > return ret; > } > + up_read(&vcpu->kvm->arch.crypto.pqap_hook_rwsem); > /* > * A vfio_driver must register a hook. > * No hook means no driver to enable the SIE CRYCB and no queues. > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c > index d65a5728153b..2998c1b53ab9 100644 > --- a/drivers/s390/crypto/vfio_ap_ops.c > +++ b/drivers/s390/crypto/vfio_ap_ops.c > @@ -342,7 +342,6 @@ static int vfio_ap_mdev_create(struct mdev_device *mdev) > init_rwsem(&matrix_mdev->rwsem); > mdev_set_drvdata(mdev, matrix_mdev); > matrix_mdev->pqap_hook.hook = handle_pqap; > - matrix_mdev->pqap_hook.owner = THIS_MODULE; > > mutex_lock(&matrix_dev->lock); > list_add(&matrix_mdev->node, &matrix_dev->mdev_list); > @@ -1063,7 +1062,6 @@ static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev, > down_write(&matrix_mdev->rwsem); > matrix_mdev->kvm = kvm; > kvm_get_kvm(kvm); > - kvm->arch.crypto.pqap_hook = &matrix_mdev->pqap_hook; > up_write(&matrix_mdev->rwsem); > > /* > @@ -1071,6 +1069,10 @@ static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev, > * masks for the KVM guest > */ > if (kvm->arch.crypto.crycbd) { > + down_write(&matrix_mdev->kvm->arch.crypto.pqap_hook_rwsem); > + kvm->arch.crypto.pqap_hook = &matrix_mdev->pqap_hook; > + up_write(&matrix_mdev->kvm->arch.crypto.pqap_hook_rwsem); > + > down_read(&matrix_mdev->matrix.rwsem); > kvm_arch_crypto_set_masks(kvm, > matrix_mdev->matrix.apm, > @@ -1122,11 +1124,15 @@ static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb, > static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev) > { > if (matrix_mdev->kvm) { > - if (matrix_mdev->kvm->arch.crypto.crycbd) > + if (matrix_mdev->kvm->arch.crypto.crycbd) { > + down_write(&matrix_mdev->kvm->arch.crypto.pqap_hook_rwsem); > + matrix_mdev->kvm->arch.crypto.pqap_hook = NULL; > + up_write(&matrix_mdev->kvm->arch.crypto.pqap_hook_rwsem); > + > kvm_arch_crypto_clear_masks(matrix_mdev->kvm); > + } > > down_write(&matrix_mdev->rwsem); > - matrix_mdev->kvm->arch.crypto.pqap_hook = NULL; > vfio_ap_mdev_reset_queues(matrix_mdev->mdev); > kvm_put_kvm(matrix_mdev->kvm); > matrix_mdev->kvm = NULL; > diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h > index a163ac04ff8a..3d6afd0faaaf 100644 > --- a/drivers/s390/crypto/vfio_ap_private.h > +++ b/drivers/s390/crypto/vfio_ap_private.h > @@ -90,7 +90,7 @@ struct ap_matrix_mdev { > struct notifier_block iommu_notifier; > struct rw_semaphore rwsem; > struct kvm *kvm; > - struct kvm_s390_module_hook pqap_hook; > + struct kvm_s390_crypto_hook pqap_hook; > struct mdev_device *mdev; > }; > >