Re: [PATCH v7 05/15] s390/vfio-ap: introduce shadow CRYCB

Tony Krowiak
2020-04-21T21:39:56Z

On 4/16/20 7:58 AM, Cornelia Huck wrote:
> On Tue, 7 Apr 2020 15:20:05 -0400
> Tony Krowiak<akrowiak@linux.ibm.com> wrote:
>
>> Let's introduce a shadow copy of the KVM guest's CRYCB and maintain it for
>> the lifespan of the guest. The shadow CRYCB will be used to provide the
>> AP configuration for a KVM guest.
> 'shadow CRYCB' seems to be a bit of a misnomer, as the real CRYCB has a
> different format (for starters, it also contains key wrapping stuff).
> It seems to be more of a 'shadow matrix'.

You make a valid point; however in reality, matrix - as it is used
throughout vfio ap - is a misnomer. The
matrix is actually comprised of the assigned APIDs and APQIs
(i.e., APQNs) and does not include the control domain assignments.
In reality, the APM, AQM and ADM are fields within the AP control
block (APCB) which is embedded within the CRYCB, so a more
accurate name might be 'shadow_apcb'. I think I'll go with that.

>> Signed-off-by: Tony Krowiak<akrowiak@linux.ibm.com>
>> ---
>> drivers/s390/crypto/vfio_ap_ops.c | 31 +++++++++++++++++++++------
>> drivers/s390/crypto/vfio_ap_private.h | 1 +
>> 2 files changed, 25 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
>> index 8ece0d52ff4c..b8b678032ab7 100644
>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>> @@ -280,14 +280,32 @@ static int handle_pqap(struct kvm_vcpu *vcpu)
>> return 0;
>> }
>>
>> +static void vfio_ap_matrix_clear(struct ap_matrix *matrix)
> vfio_ap_matrix_clear_masks()?

Sure, that works.

>
>> +{
>> + bitmap_clear(matrix->apm, 0, AP_DEVICES);
>> + bitmap_clear(matrix->aqm, 0, AP_DOMAINS);
>> + bitmap_clear(matrix->adm, 0, AP_DOMAINS);
>> +}
>> +
>> static void vfio_ap_matrix_init(struct ap_config_info *info,
>> struct ap_matrix *matrix)
>> {
>> + vfio_ap_matrix_clear(matrix);
>> matrix->apm_max = info->apxa ? info->Na : 63;
>> matrix->aqm_max = info->apxa ? info->Nd : 15;
>> matrix->adm_max = info->apxa ? info->Nd : 15;
>> }
>>
>> +static bool vfio_ap_mdev_commit_crycb(struct ap_matrix_mdev *matrix_mdev)
> vfio_ap_mdev_commit_masks()?

Since I am changing the name of shadow_crycb to shadow_apcb,
it probably makes more sense to rename this to
vfio_ap_mdev_commit_apcb().

>
> And it does not seem to return anything? (Maybe it should, to be
> consumed below?)

In patch 7, the check at the beginning of this function (for a CRYCB)
is moved into the vfio_ap_mdev_has_crycb() function, so there is
no need to return anything from this function. I will introduce the
vfio_ap_mdev_has_crycb() function in this patch instead for the
next submission.

>
>> +{
>> + if (matrix_mdev->kvm && matrix_mdev->kvm->arch.crypto.crycbd) {
>> + kvm_arch_crypto_set_masks(matrix_mdev->kvm,
>> + matrix_mdev->shadow_crycb.apm,
>> + matrix_mdev->shadow_crycb.aqm,
>> + matrix_mdev->shadow_crycb.adm);
>> + }
>> +}
>> +
>> static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
>> {
>> struct ap_matrix_mdev *matrix_mdev;
>> @@ -303,6 +321,7 @@ static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
>>
>> matrix_mdev->mdev = mdev;
>> vfio_ap_matrix_init(&matrix_dev->info, &matrix_mdev->matrix);
>> + vfio_ap_matrix_init(&matrix_dev->info, &matrix_mdev->shadow_crycb);
>> mdev_set_drvdata(mdev, matrix_mdev);
>> matrix_mdev->pqap_hook.hook = handle_pqap;
>> matrix_mdev->pqap_hook.owner = THIS_MODULE;
>> @@ -1126,13 +1145,9 @@ 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)
>> - 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_crycb, &matrix_mdev->matrix,
>> + sizeof(matrix_mdev->shadow_crycb));
>> + vfio_ap_mdev_commit_crycb(matrix_mdev);
> You are changing the return code for !crycb; maybe that's where a good
> return code for vfio_ap_mdev_commit_crycb() would come in handy :)

See my comments above regarding moving the introduction of the
vfio_ap_mdev_has_crycb() function from patch 7 to this patch.
In that case, that function will be called here before committing.

>
>>
>> return NOTIFY_OK;
>> }
>> @@ -1247,6 +1262,8 @@ static void vfio_ap_mdev_release(struct mdev_device *mdev)
>> kvm_put_kvm(matrix_mdev->kvm);
>> matrix_mdev->kvm = NULL;
>> }
>> +
>> + vfio_ap_matrix_clear(&matrix_mdev->shadow_crycb);
>> mutex_unlock(&matrix_dev->lock);
>>
>> vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
>> diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
>> index 4b6e144bab17..87cc270c3212 100644
>> --- a/drivers/s390/crypto/vfio_ap_private.h
>> +++ b/drivers/s390/crypto/vfio_ap_private.h
>> @@ -83,6 +83,7 @@ struct ap_matrix {
>> struct ap_matrix_mdev {
>> struct list_head node;
>> struct ap_matrix matrix;
>> + struct ap_matrix shadow_crycb;
> I think shadow_matrix would be a better name.

Changing to shadow_apcb as per comments above.

>
>> struct notifier_block group_notifier;
>> struct notifier_block iommu_notifier;
>> struct kvm *kvm;