Re: [PATCH v6 3/7] s390: ap: setup relation betwen KVM and mediated device

Tony Krowiak
2019-03-28T16:12:17Z

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:
>