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    SubjectRe: [PATCH v6 3/7] s390: ap: setup relation betwen KVM and mediated device
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    On 3/22/19 10:43 AM, Pierre Morel wrote:
    > When the mediated device is open we setup the relation with KVM unset it
    > when the mediated device is released.

    s/open we setup/open, we set up/
    s/with KVM unset/with KVM and unset/

    >
    > We lock the matrix mediated device to avoid any change until the
    > open is done.
    > We make sure that KVM is present when opening the mediated device
    > otherwise we return an error.

    s/mediated device/mediated device,/

    >
    > Increase kvm's refcount to ensure the KVM structures are still available
    > during the use of the mediated device by the guest.
    >
    > Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
    > ---
    > drivers/s390/crypto/vfio_ap_ops.c | 143 +++++++++++++++++++++-----------------
    > 1 file changed, 79 insertions(+), 64 deletions(-)
    >
    > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
    > index 77f7bac..bdb36e0 100644
    > --- a/drivers/s390/crypto/vfio_ap_ops.c
    > +++ b/drivers/s390/crypto/vfio_ap_ops.c
    > @@ -787,74 +787,24 @@ static const struct attribute_group *vfio_ap_mdev_attr_groups[] = {
    > NULL
    > };
    >
    > -/**
    > - * vfio_ap_mdev_set_kvm
    > - *
    > - * @matrix_mdev: a mediated matrix device
    > - * @kvm: reference to KVM instance
    > - *
    > - * Verifies no other mediated matrix device has @kvm and sets a reference to
    > - * it in @matrix_mdev->kvm.
    > - *
    > - * Return 0 if no other mediated matrix device has a reference to @kvm;
    > - * otherwise, returns an -EPERM.
    > - */
    > -static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev,
    > - struct kvm *kvm)
    > -{
    > - 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);
    > - return -EPERM;
    > - }
    > - }
    > -
    > - matrix_mdev->kvm = kvm;
    > - mutex_unlock(&matrix_dev->lock);
    > -
    > - return 0;
    > -}
    > -
    > static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
    > unsigned long action, void *data)
    > {
    > - int ret;
    > 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);
    > -
    > - if (!data) {
    > - matrix_mdev->kvm = NULL;
    > - return NOTIFY_OK;
    > - }
    > -
    > - ret = vfio_ap_mdev_set_kvm(matrix_mdev, data);
    > - if (ret)
    > - return 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;
    > -
    > - kvm_arch_crypto_set_masks(matrix_mdev->kvm, matrix_mdev->matrix.apm,
    > - matrix_mdev->matrix.aqm,
    > - matrix_mdev->matrix.adm);
    > + matrix_mdev->kvm = data;
    >
    > return NOTIFY_OK;
    > }
    >
    > -static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
    > +static int vfio_ap_mdev_reset_queues(struct ap_matrix_mdev *matrix_mdev)
    > {
    > int ret;
    > int rc = 0;
    > - struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
    > struct vfio_ap_queue *q;
    >
    > list_for_each_entry(q, &matrix_mdev->qlist, list) {
    > @@ -871,41 +821,106 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
    > return rc;
    > }
    >
    > +/**
    > + * vfio_ap_mdev_set_kvm
    > + *
    > + * @matrix_mdev: a mediated matrix device
    > + *
    > + * - Verifies that the hook is free and install the PQAP hook
    > + * - Copy the matrix masks inside the CRYCB
    > + * - Increment the KVM rerference count
    > + *
    > + * Return 0 if no other mediated matrix device has a reference to @kvm;
    > + * otherwise, returns an -EPERM.
    > + */
    > +static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev)
    > +{
    > + if (matrix_mdev->kvm->arch.crypto.pqap_hook)
    > + return -EPERM;

    How would this happen; in other words, why are we checking this?

    > + matrix_mdev->kvm->arch.crypto.pqap_hook = &matrix_mdev->pqap_hook;
    > +
    > + kvm_arch_crypto_set_masks(matrix_mdev->kvm, matrix_mdev->matrix.apm,
    > + matrix_mdev->matrix.aqm,
    > + matrix_mdev->matrix.adm);
    > +
    > + kvm_get_kvm(matrix_mdev->kvm);
    > + return 0;
    > +}
    > +
    > +/**
    > + * vfio_ap_mdev_unset_kvm
    > + *
    > + * @matrix_mdev: a mediated matrix device
    > + *
    > + * - Clears the matrix masks inside the CRYCB
    > + * - Reset the queues before to clear the hook in case IRQ happen during
    > + * reset.
    > + * - Clears the hook
    > + * - Decrement the KVM rerference count
    > + */
    > +static int vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev)
    > +{
    > + struct kvm *kvm = matrix_mdev->kvm;
    > +
    > + kvm_arch_crypto_clear_masks(matrix_mdev->kvm);
    > + vfio_ap_mdev_reset_queues(matrix_mdev);
    > + matrix_mdev->kvm->arch.crypto.pqap_hook = NULL;
    > + matrix_mdev->kvm = NULL;
    > + kvm_put_kvm(kvm);
    > + return 0;
    > +}
    > +
    > static int vfio_ap_mdev_open(struct mdev_device *mdev)
    > {
    > struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
    > unsigned long events;
    > int ret;
    >
    > + mutex_lock(&matrix_dev->lock);
    >
    > - if (!try_module_get(THIS_MODULE))
    > - return -ENODEV;
    > + if (!try_module_get(THIS_MODULE)) {
    > + ret = -ENODEV;
    > + goto unlock;
    > + }
    >
    > matrix_mdev->group_notifier.notifier_call = vfio_ap_mdev_group_notifier;
    > events = VFIO_GROUP_NOTIFY_SET_KVM;
    >
    > ret = vfio_register_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
    > &events, &matrix_mdev->group_notifier);
    > - if (ret) {
    > - module_put(THIS_MODULE);
    > - return ret;
    > + if (ret)
    > + goto put_unlock;
    > +
    > + /* We do not support opening the mediated device without KVM */
    > + if (!matrix_mdev->kvm) {
    > + ret = -ENOENT;
    > + goto free_notifier;
    > }
    >
    > - return 0;
    > + ret = vfio_ap_mdev_set_kvm(matrix_mdev);
    > + if (!ret)
    > + goto unlock;
    > +
    > +free_notifier:
    > + vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
    > + &matrix_mdev->group_notifier);
    > +put_unlock:
    > + module_put(THIS_MODULE);
    > +unlock:
    > + mutex_unlock(&matrix_dev->lock);
    > + return ret;
    > }
    >
    > static void vfio_ap_mdev_release(struct mdev_device *mdev)
    > {
    > struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
    >
    > - if (matrix_mdev->kvm)
    > - kvm_arch_crypto_clear_masks(matrix_mdev->kvm);
    > -
    > - matrix_mdev->kvm = NULL;
    > - vfio_ap_mdev_reset_queues(mdev);
    > + mutex_lock(&matrix_dev->lock);
    > + vfio_ap_mdev_unset_kvm(matrix_mdev);
    > vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
    > &matrix_mdev->group_notifier);
    > module_put(THIS_MODULE);
    > + mutex_unlock(&matrix_dev->lock);
    > }
    >
    > static int vfio_ap_mdev_get_device_info(unsigned long arg)
    > @@ -939,7 +954,7 @@ static ssize_t vfio_ap_mdev_ioctl(struct mdev_device *mdev,
    > break;
    > case VFIO_DEVICE_RESET:
    > mutex_lock(&matrix_dev->lock);
    > - ret = vfio_ap_mdev_reset_queues(mdev);
    > + ret = vfio_ap_mdev_reset_queues(mdev_get_drvdata(mdev));
    > mutex_unlock(&matrix_dev->lock);
    > break;
    > default:
    >

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