From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:55834 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726689AbgLCR4I (ORCPT ); Thu, 3 Dec 2020 12:56:08 -0500 Date: Thu, 3 Dec 2020 18:55:14 +0100 From: Halil Pasic Subject: Re: [PATCH] s390/vfio-ap: Clean up vfio_ap resources when KVM pointer invalidated Message-ID: <20201203185514.54060568.pasic@linux.ibm.com> In-Reply-To: <20201202234101.32169-1-akrowiak@linux.ibm.com> References: <20201202234101.32169-1-akrowiak@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit List-ID: To: Tony Krowiak Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, borntraeger@de.ibm.com, cohuck@redhat.com, alex.williamson@redhat.com, kwankhede@nvidia.com, david@redhat.com On Wed, 2 Dec 2020 18:41:01 -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 stashes the pointer > and calls the kvm_get_kvm() function to increment its reference counter. > When the notifier is called to make notification that the KVM pointer has > been set to NULL, the driver should clean up any resources associated with > the KVM pointer and decrement its reference counter. The current > implementation does not take care of this clean up. > > Signed-off-by: Tony Krowiak Do we need a Fixes tag? Do we need this backported? In my opinion this is necessary since the interrupt patches. > --- > drivers/s390/crypto/vfio_ap_ops.c | 21 +++++++++++++-------- > 1 file changed, 13 insertions(+), 8 deletions(-) > > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c > index e0bde8518745..eeb9c9130756 100644 > --- a/drivers/s390/crypto/vfio_ap_ops.c > +++ b/drivers/s390/crypto/vfio_ap_ops.c > @@ -1083,6 +1083,17 @@ static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb, > return NOTIFY_DONE; > } > > +static void vfio_ap_mdev_put_kvm(struct ap_matrix_mdev *matrix_mdev) I don't like the name. The function does more that put_kvm. Maybe something like _disconnect_kvm()? > +{ > + if (matrix_mdev->kvm) { > + (matrix_mdev->kvm); > + matrix_mdev->kvm->arch.crypto.pqap_hook = NULL; Is a plain assignment to arch.crypto.pqap_hook apropriate, or do we need to take more care? For instance kvm_arch_crypto_set_masks() takes kvm->lock before poking kvm->arch.crypto.crycb. > + 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) > { > @@ -1095,7 +1106,7 @@ static int vfio_ap_mdev_group_notifier(struct notifier_block *nb, > matrix_mdev = container_of(nb, struct ap_matrix_mdev, group_notifier); > > if (!data) { > - matrix_mdev->kvm = NULL; > + vfio_ap_mdev_put_kvm(matrix_mdev); The lock question was already raised. What are the exact circumstances under which this branch can be taken? > return NOTIFY_OK; > } > > @@ -1222,13 +1233,7 @@ static void vfio_ap_mdev_release(struct mdev_device *mdev) > struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev); > > mutex_lock(&matrix_dev->lock); > - if (matrix_mdev->kvm) { > - kvm_arch_crypto_clear_masks(matrix_mdev->kvm); > - matrix_mdev->kvm->arch.crypto.pqap_hook = NULL; > - vfio_ap_mdev_reset_queues(mdev); > - kvm_put_kvm(matrix_mdev->kvm); > - matrix_mdev->kvm = NULL; > - } > + vfio_ap_mdev_put_kvm(matrix_mdev); > mutex_unlock(&matrix_dev->lock); > > vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,