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Tue, 15 Dec 2020 10:57:48 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3270311C052; Tue, 15 Dec 2020 10:57:48 +0000 (GMT) Received: from oc2783563651 (unknown [9.171.86.205]) by d06av25.portsmouth.uk.ibm.com (Postfix) with SMTP; Tue, 15 Dec 2020 10:57:48 +0000 (GMT) Date: Tue, 15 Dec 2020 11:57:46 +0100 From: Halil Pasic To: Tony Krowiak Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, stable@vger.kernel.org, gregkh@linuxfoundation.org, sashal@kernel.org, borntraeger@de.ibm.com, cohuck@redhat.com, kwankhede@nvidia.com, pbonzini@redhat.com, alex.williamson@redhat.com, pasic@linux.vnet.ibm.com Subject: Re: [PATCH v3] s390/vfio-ap: clean up vfio_ap resources when KVM pointer invalidated Message-ID: <20201215115746.3552e873.pasic@linux.ibm.com> In-Reply-To: <20201214165617.28685-1-akrowiak@linux.ibm.com> References: <20201214165617.28685-1-akrowiak@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343,18.0.737 definitions=2020-12-15_08:2020-12-14,2020-12-15 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 mlxlogscore=999 bulkscore=0 phishscore=0 malwarescore=0 priorityscore=1501 suspectscore=0 mlxscore=0 spamscore=0 impostorscore=0 clxscore=1011 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012150070 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 14 Dec 2020 11:56:17 -0500 Tony Krowiak wrote: > The vfio_ap device driver registers a group notifier with VFIO when the > file descriptor for a VFIO mediated device for a KVM guest is opened to > receive notification that the KVM pointer is set (VFIO_GROUP_NOTIFY_SET_KVM > event). When the KVM pointer is set, the vfio_ap driver takes the > following actions: > 1. Stashes the KVM pointer in the vfio_ap_mdev struct that holds the state > of the mediated device. > 2. Calls the kvm_get_kvm() function to increment its reference counter. > 3. Sets the function pointer to the function that handles interception of > the instruction that enables/disables interrupt processing. > 4. Sets the masks in the KVM guest's CRYCB to pass AP resources through to > the guest. > > In order to avoid memory leaks, when the notifier is called to receive > notification that the KVM pointer has been set to NULL, the vfio_ap device > driver should reverse the actions taken when the KVM pointer was set. > > Fixes: 258287c994de ("s390: vfio-ap: implement mediated device open callback") > Signed-off-by: Tony Krowiak > --- > drivers/s390/crypto/vfio_ap_ops.c | 29 ++++++++++++++++++++--------- > 1 file changed, 20 insertions(+), 9 deletions(-) > > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c > index e0bde8518745..cd22e85588e1 100644 > --- a/drivers/s390/crypto/vfio_ap_ops.c > +++ b/drivers/s390/crypto/vfio_ap_ops.c > @@ -1037,8 +1037,6 @@ static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev, > { > struct ap_matrix_mdev *m; > > - mutex_lock(&matrix_dev->lock); > - > list_for_each_entry(m, &matrix_dev->mdev_list, node) { > if ((m != matrix_mdev) && (m->kvm == kvm)) { > mutex_unlock(&matrix_dev->lock); > @@ -1049,7 +1047,6 @@ static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev, > matrix_mdev->kvm = kvm; > kvm_get_kvm(kvm); > kvm->arch.crypto.pqap_hook = &matrix_mdev->pqap_hook; > - mutex_unlock(&matrix_dev->lock); > > return 0; > } > @@ -1083,35 +1080,49 @@ static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb, > return NOTIFY_DONE; > } > > +static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev) > +{ > + kvm_arch_crypto_clear_masks(matrix_mdev->kvm); > + matrix_mdev->kvm->arch.crypto.pqap_hook = NULL; This patch LGTM. The only concern I have with it is whether a different cpu is guaranteed to observe the above assignment as an atomic operation. I think we didn't finish this discussion at v1, or did we? Regards, Halil > + vfio_ap_mdev_reset_queues(matrix_mdev->mdev); > + kvm_put_kvm(matrix_mdev->kvm); > + matrix_mdev->kvm = NULL; > +} > + > static int vfio_ap_mdev_group_notifier(struct notifier_block *nb, > unsigned long action, void *data) > { > - int ret; > + int ret, notify_rc = NOTIFY_DONE; > struct ap_matrix_mdev *matrix_mdev; > > if (action != VFIO_GROUP_NOTIFY_SET_KVM) > return NOTIFY_OK; > > matrix_mdev = container_of(nb, struct ap_matrix_mdev, group_notifier); > + mutex_lock(&matrix_dev->lock); > > if (!data) { > - matrix_mdev->kvm = NULL; > - return NOTIFY_OK; > + if (matrix_mdev->kvm) > + vfio_ap_mdev_unset_kvm(matrix_mdev); > + notify_rc = NOTIFY_OK; > + goto notify_done; > } > > ret = vfio_ap_mdev_set_kvm(matrix_mdev, data); > if (ret) > - return NOTIFY_DONE; > + goto notify_done; > > /* If there is no CRYCB pointer, then we can't copy the masks */ > if (!matrix_mdev->kvm->arch.crypto.crycbd) > - return NOTIFY_DONE; > + goto notify_done; > > kvm_arch_crypto_set_masks(matrix_mdev->kvm, matrix_mdev->matrix.apm, > matrix_mdev->matrix.aqm, > matrix_mdev->matrix.adm); > > - return NOTIFY_OK; > +notify_done: > + mutex_unlock(&matrix_dev->lock); > + return notify_rc; > } > > static void vfio_ap_irq_disable_apqn(int apqn)