Re: [PATCH v10 06/16] s390/vfio-ap: introduce shadow APCB

Cornelia Huck
2020-09-17T14:23:03Z

On Fri, 21 Aug 2020 15:56:06 -0400
Tony Krowiak <akrowiak@linux.ibm.com> wrote:

> The APCB is a field within the CRYCB that provides the AP configuration
> to a KVM guest. Let's introduce a shadow copy of the KVM guest's APCB and
> maintain it for the lifespan of the guest.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
> drivers/s390/crypto/vfio_ap_ops.c | 32 ++++++++++++++++++++++-----
> drivers/s390/crypto/vfio_ap_private.h | 2 ++
> 2 files changed, 29 insertions(+), 5 deletions(-)

(...)

> @@ -1202,13 +1223,12 @@ static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
> 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)
> + if (!vfio_ap_mdev_has_crycb(matrix_mdev))
> return NOTIFY_DONE;
>
> - kvm_arch_crypto_set_masks(matrix_mdev->kvm, matrix_mdev->matrix.apm,
> - matrix_mdev->matrix.aqm,
> - matrix_mdev->matrix.adm);
> + memcpy(&matrix_mdev->shadow_apcb, &matrix_mdev->matrix,
> + sizeof(matrix_mdev->shadow_apcb));
> + vfio_ap_mdev_commit_crycb(matrix_mdev);

We are sure that the shadow APCB always matches up as we are the only
ones manipulating the APCB in the CRYCB, right?

>
> return NOTIFY_OK;
> }