Re: [PATCH v2 2/7] s390: vfio-ap: maintain a shadow of the guest's CRYCB

[Tony Krowiak <akrowiak@linux.ibm.com>]

On 5/7/19 4:22 AM, Pierre Morel wrote:
> On 06/05/2019 21:53, Tony Krowiak wrote:
>> On 5/6/19 2:49 AM, Pierre Morel wrote:
>>> On 03/05/2019 23:14, Tony Krowiak wrote:
>>>> This patch introduces a shadow of the CRYCB being used by a guest. This
>>>> will enable to more effectively manage dynamic changes to the AP
>>>> resources installed on the host that may be assigned to an mdev device
>>>> and being used by a guest. For example:
>>>>
>>>> * AP adapter cards can be dynamically added to and removed from the AP
>>>>    configuration via the SE or an SCLP command.
>>>>
>>>> * AP resources that disappear and reappear due to hardware 
>>>> malfunctions.
>>>>
>>>> * AP queues bound to and unbound from the vfio_ap device driver by a
>>>>    root user.
>>>>
>>>> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
>>>> ---
>>>>   drivers/s390/crypto/vfio_ap_ops.c     | 91 
>>>> ++++++++++++++++++++++++++++++++---
>>>>   drivers/s390/crypto/vfio_ap_private.h |  2 +
>>>>   2 files changed, 87 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c 
>>>> b/drivers/s390/crypto/vfio_ap_ops.c
>>>> index b88a2a2ba075..44a04b4aa9ae 100644
>>>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>>>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>>>> @@ -297,6 +297,45 @@ static void 
>>>> vfio_ap_mdev_wait_for_qempty(unsigned long apid, unsigned long apqi)
>>>>       } while (--retry);
>>>>   }
>>>> +/*
>>>> + * vfio_ap_mdev_update_crycb
>>>> + *
>>>> + * @matrix_mdev: the mediated matrix device
>>>> + *
>>>> + * Updates the AP matrix in the guest's CRYCB from it's shadow masks.
>>>> + *
>>>> + * Returns zero if the guest's CRYCB is successfully updated; 
>>>> otherwise,
>>>> + * returns -ENODEV if a guest is not running or does not have a CRYCB.
>>>> + */
>>>> +static int vfio_ap_mdev_update_crycb(struct ap_matrix_mdev 
>>>> *matrix_mdev)
>>>> +{
>>>> +    if (!matrix_mdev->kvm || !matrix_mdev->kvm->arch.crypto.crycbd)
>>>> +        return -ENODEV;
>>>> +
>>>> +    kvm_arch_crypto_set_masks(matrix_mdev->kvm,
>>>> +                  matrix_mdev->shadow_crycb->apm,
>>>> +                  matrix_mdev->shadow_crycb->aqm,
>>>> +                  matrix_mdev->shadow_crycb->adm);
>>>> +
>>>> +    return 0;
>>>> +}
>>>> +
>>>> +static int match_apqn(struct device *dev, void *data)
>>>> +{
>>>> +    struct ap_queue *apq = to_ap_queue(dev);
>>>> +
>>>> +    return (apq->qid == *(unsigned long *)(data)) ? 1 : 0;
>>>> +}
>>>> +
>>>> +static struct device *vfio_ap_get_queue_dev(unsigned long apid,
>>>> +                         unsigned long apqi)
>>>> +{
>>>> +    unsigned long apqn = AP_MKQID(apid, apqi);
>>>> +
>>>> +    return driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL,
>>>> +                  &apqn, match_apqn);
>>>> +}
>>>> +
>>>>   /**
>>>>    * assign_adapter_store
>>>>    *
>>>> @@ -805,14 +844,9 @@ 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)
>>>> +    if (vfio_ap_mdev_update_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);
>>>> -
>>>>       return NOTIFY_OK;
>>>>   }
>>>> @@ -867,12 +901,55 @@ static int vfio_ap_mdev_reset_queues(struct 
>>>> mdev_device *mdev)
>>>>       return rc;
>>>>   }
>>>> +static int vfio_ap_mdev_create_shadow_crycb(struct ap_matrix_mdev 
>>>> *matrix_mdev)
>>>> +{
>>>> +    unsigned long apid, apqi, domid;
>>>> +    struct device *dev;
>>>> +
>>>> +    matrix_mdev->shadow_crycb = 
>>>> kzalloc(sizeof(*matrix_mdev->shadow_crycb),
>>>> +                        GFP_KERNEL);
>>>> +    if (!matrix_mdev->shadow_crycb)
>>>> +        return -ENOMEM;
>>>> +
>>>> +    vfio_ap_matrix_init(&matrix_dev->info, matrix_mdev->shadow_crycb);
>>>> +
>>>> +    /*
>>>> +     * Examine each APQN assigned to the mdev device. Set the APID 
>>>> and APQI
>>>> +     * in the shadow CRYCB if and only if the queue device 
>>>> identified by
>>>> +     * the APQN is in the configuration.
>>>> +     */
>>>> +    for_each_set_bit_inv(apid, matrix_mdev->matrix.apm,
>>>> +                 matrix_mdev->matrix.apm_max + 1) {
>>>> +        for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm,
>>>> +                     matrix_mdev->matrix.aqm_max + 1) {
>>>> +            dev = vfio_ap_get_queue_dev(apid, apqi);
>>>> +            if (dev) {
>>>> +                set_bit_inv(apid,
>>>> +                        matrix_mdev->shadow_crycb->apm);
>>>> +                set_bit_inv(apqi,
>>>> +                        matrix_mdev->shadow_crycb->aqm);
>>>> +                put_device(dev);
>>>> +            }
>>>
>>> I think that if we do not find a device here we have a problem.
>>> Don't we?
>>
>> Other than the fact that the guest will not have any AP devices,
>> what would be the problem? What would you suggest?
>>
> 
> Suppose we have in matrix_mdev->matrix:
> 1-2
> 1-3
> 2-2
> 2-3
> 
> We set the shadow_crycb with:
> we find 1-2 we set 1 2
> we find 1-3 we se 1 3
> we find 2-2 we set 2 2
> we do not find 2-3
> 
> we have set apm(1,2) aqm(2,3)
> the guest can access 2-3 but we do not have the device.

Good point. I'll fix this for v4.

> 
> Pierre
>