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

[Tony Krowiak]

On 9/17/20 10:22 AM, Cornelia Huck wrote:
> On Fri, 21 Aug 2020 15:56:06 -0400
> Tony Krowiak <akrowiak@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> > ---
> >   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?

Yes

> >   
> >   	return NOTIFY_OK;
> >   }