Messages in this thread | | | Date | Fri, 27 May 2022 08:41:46 -0400 | Subject | Re: [PATCH v19 09/20] s390/vfio-ap: use proper locking order when setting/clearing KVM pointer | From | "Jason J. Herne" <> |
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On 4/4/22 18:10, Tony Krowiak wrote: > The group notifier that handles the VFIO_GROUP_NOTIFY_SET_KVM event must > use the required locks in proper locking order to dynamically update the > guest's APCB. The proper locking order is: > > 1. matrix_dev->guests_lock: required to use the KVM pointer to > update a KVM guest's APCB. > > 2. matrix_mdev->kvm->lock: required to update a KVM guest's APCB. > > 3. matrix_dev->mdevs_lock: required to store or access the data > stored in a struct ap_matrix_mdev instance. > > Two macros are introduced to acquire and release the locks in the proper > order. These macros are now used by the group notifier functions. > > Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> > --- > drivers/s390/crypto/vfio_ap_ops.c | 56 +++++++++++++++++++++++++------ > 1 file changed, 46 insertions(+), 10 deletions(-) > > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c > index 077b8c9c831b..757bbf449b04 100644 > --- a/drivers/s390/crypto/vfio_ap_ops.c > +++ b/drivers/s390/crypto/vfio_ap_ops.c > @@ -30,6 +30,47 @@ static int vfio_ap_mdev_reset_queues(struct ap_matrix_mdev *matrix_mdev); > static struct vfio_ap_queue *vfio_ap_find_queue(int apqn); > static const struct vfio_device_ops vfio_ap_matrix_dev_ops; > > +/** > + * get_update_locks_for_kvm: Acquire the locks required to dynamically update a > + * KVM guest's APCB in the proper order. > + * > + * @kvm: a pointer to a struct kvm object containing the KVM guest's APCB. > + * > + * The proper locking order is: > + * 1. matrix_dev->guests_lock: required to use the KVM pointer to update a KVM > + * guest's APCB. > + * 2. kvm->lock: required to update a guest's APCB > + * 3. matrix_dev->mdevs_lock: required to access data stored in a matrix_mdev > + * > + * Note: If @kvm is NULL, the KVM lock will not be taken. > + */ > +#define get_update_locks_for_kvm(kvm) ({ \ > + mutex_lock(&matrix_dev->guests_lock); \ > + if (kvm) \ > + mutex_lock(&kvm->lock); \ > + mutex_lock(&matrix_dev->mdevs_lock); \ > +}) > + > +/** > + * release_update_locks_for_kvm: Release the locks used to dynamically update a > + * KVM guest's APCB in the proper order. > + * > + * @kvm: a pointer to a struct kvm object containing the KVM guest's APCB. > + * > + * The proper unlocking order is: > + * 1. matrix_dev->mdevs_lock > + * 2. kvm->lock > + * 3. matrix_dev->guests_lock > + * > + * Note: If @kvm is NULL, the KVM lock will not be released. > + */ > +#define release_update_locks_for_kvm(kvm) ({ \ > + mutex_unlock(&matrix_dev->mdevs_lock); \ > + if (kvm) \ > + mutex_unlock(&kvm->lock); \ > + mutex_unlock(&matrix_dev->guests_lock); \ > +}) > + > /** > * vfio_ap_mdev_get_queue - retrieve a queue with a specific APQN from a > * hash table of queues assigned to a matrix mdev > @@ -1263,13 +1304,11 @@ static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev, > kvm->arch.crypto.pqap_hook = &matrix_mdev->pqap_hook; > up_write(&kvm->arch.crypto.pqap_hook_rwsem); > > - mutex_lock(&kvm->lock); > - mutex_lock(&matrix_dev->mdevs_lock); > + get_update_locks_for_kvm(kvm); > > list_for_each_entry(m, &matrix_dev->mdev_list, node) { > if (m != matrix_mdev && m->kvm == kvm) { > - mutex_unlock(&kvm->lock); > - mutex_unlock(&matrix_dev->mdevs_lock); > + release_update_locks_for_kvm(kvm); > return -EPERM; > } > } > @@ -1280,8 +1319,7 @@ static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev, > matrix_mdev->shadow_apcb.aqm, > matrix_mdev->shadow_apcb.adm); > > - mutex_unlock(&kvm->lock); > - mutex_unlock(&matrix_dev->mdevs_lock); > + release_update_locks_for_kvm(kvm); > } > > return 0; > @@ -1332,16 +1370,14 @@ static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev) > kvm->arch.crypto.pqap_hook = NULL; > up_write(&kvm->arch.crypto.pqap_hook_rwsem); > > - mutex_lock(&kvm->lock); > - mutex_lock(&matrix_dev->mdevs_lock); > + get_update_locks_for_kvm(kvm); > > kvm_arch_crypto_clear_masks(kvm); > vfio_ap_mdev_reset_queues(matrix_mdev); > kvm_put_kvm(kvm); > matrix_mdev->kvm = NULL; > > - mutex_unlock(&kvm->lock); > - mutex_unlock(&matrix_dev->mdevs_lock); > + release_update_locks_for_kvm(kvm); > } > } >
In isolation... Reviewed-by: Jason J. Herne <jjherne@linux.ibm.com>
-- -- Jason J. Herne (jjherne@linux.ibm.com)
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