Re: [PATCH v5 4/7] s390: ap: setup relation betwen KVM and mediated device

Halil Pasic
2019-03-15T18:15:57Z

On Wed, 13 Mar 2019 17:05:01 +0100
Pierre Morel <pmorel@linux.ibm.com> wrote:

> When the mediated device is open we setup the relation with KVM unset it
> when the mediated device is released.
>
> We ensure KVM is present on opening of the mediated device.
>
> We ensure that KVM survives the mediated device, and establish a direct

survives?

> link from KVM to the mediated device to simplify the relationship.
>
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
> drivers/s390/crypto/vfio_ap_ops.c | 80 ++++++++++++++++++++++-----------------
> 1 file changed, 46 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 0f8952c23..6b559ca 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -790,7 +790,6 @@ static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb,
> * 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.
> @@ -798,53 +797,39 @@ static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb,
> * 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)
> +static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev)
> {
> - struct ap_matrix_mdev *m;
> -
> mutex_lock(&matrix_dev->lock);
> + if (matrix_mdev->kvm->arch.crypto.pqap_hook)
> + goto err_unlock;
>
> - list_for_each_entry(m, &matrix_dev->mdev_list, node) {
> - if ((m != matrix_mdev) && (m->kvm == kvm)) {
> - mutex_unlock(&matrix_dev->lock);
> - return -EPERM;
> - }
> - }
> + if (!matrix_mdev->kvm->arch.crypto.crycbd)
> + goto err_unlock;
>
> - matrix_mdev->kvm = kvm;
> - mutex_unlock(&matrix_dev->lock);
> + 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);
> + mutex_unlock(&matrix_dev->lock);
> return 0;
> +
> +err_unlock:
> + mutex_unlock(&matrix_dev->lock);
> + return -EPERM;
> }
>
> 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;
> }
> @@ -888,6 +873,12 @@ static int vfio_ap_mdev_open(struct mdev_device *mdev)
> if (ret)
> goto err_group;
>
> + /* We do not support opening the mediated device without KVM */
> + if (!matrix_mdev->kvm) {
> + ret = -ENODEV;
> + goto err_group;
> + }
> +
> matrix_mdev->iommu_notifier.notifier_call = vfio_ap_mdev_iommu_notifier;
> events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
>
> @@ -896,8 +887,15 @@ static int vfio_ap_mdev_open(struct mdev_device *mdev)
> if (ret)
> goto err_iommu;
>
> + ret = vfio_ap_mdev_set_kvm(matrix_mdev);

At this point the matrix_mdev->kvm ain't guaranteed to be valid IMHO. Or
am I wrong? If I'm right kvm_get_kvm(matrix_mdev->kvm) could be too late.

> + if (ret)
> + goto err_kvm;
> +
> return 0;
>
> +err_kvm:
> + vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> + &matrix_mdev->iommu_notifier);
> err_iommu:
> vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
> &matrix_mdev->group_notifier);
> @@ -906,19 +904,33 @@ static int vfio_ap_mdev_open(struct mdev_device *mdev)
> return ret;
> }
>
> -static void vfio_ap_mdev_release(struct mdev_device *mdev)
> +static int vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev)
> {
> - struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> + struct kvm *kvm = matrix_mdev->kvm;
>
> if (matrix_mdev->kvm)
> kvm_arch_crypto_clear_masks(matrix_mdev->kvm);

This still conditional?

> -
> + vfio_ap_mdev_reset_queues(matrix_mdev->mdev);

I guess your intention was to move vfio_ap_mdev_reset_queues()
here from vfio_ap_mdev_release(), but you still have a
vfio_ap_mdev_reset_queues() call in vfio_ap_mdev_release().

> + matrix_mdev->kvm->arch.crypto.pqap_hook = NULL;
> matrix_mdev->kvm = NULL;
> +
> + kvm_put_kvm(kvm);
> + return 0;
> +}
> +
> +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);
> +
> vfio_ap_mdev_reset_queues(mdev);

Here.

Regards,
Halil

> + vfio_ap_mdev_unset_kvm(matrix_mdev);
> vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> &matrix_mdev->iommu_notifier);
> vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
> &matrix_mdev->group_notifier);
> + mutex_unlock(&matrix_dev->lock);
> module_put(THIS_MODULE);
> }
>