On Wed, 2 Dec 2020 18:41:01 -0500
Tony Krowiak <akrowiak@xxxxxxxxxxxxx> 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 <akrowiak@xxxxxxxxxxxxx>
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,
