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

[Tony Krowiak <akrowiak@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
> > ---
> >   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?

> > +        }
> > +    }
> > +
> > +    /* Set all control domains assigned to the mdev in the shadow 
> > CRYCB */
> > +    for_each_set_bit_inv(domid, matrix_mdev->matrix.adm,
> > +                 matrix_mdev->matrix.adm_max + 1)
> > +        set_bit_inv(domid, matrix_mdev->shadow_crycb->adm);
> > +
> > +    return 0;
> > +}
> > +
> >   static int vfio_ap_mdev_open(struct mdev_device *mdev)
> >   {
> >       struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> >       unsigned long events;
> >       int ret;
> > +    ret = vfio_ap_mdev_create_shadow_crycb(matrix_mdev);
> > +    if (ret)
> > +        return ret;
> >       if (!try_module_get(THIS_MODULE))
> >           return -ENODEV;
> > @@ -902,6 +979,8 @@ static void vfio_ap_mdev_release(struct 
> > mdev_device *mdev)
> >                    &matrix_mdev->group_notifier);
> >       matrix_mdev->kvm = NULL;
> >       module_put(THIS_MODULE);
> > +    kfree(matrix_mdev->shadow_crycb);
> > +    matrix_mdev->shadow_crycb = NULL;
> >   }
> >   static int vfio_ap_mdev_get_device_info(unsigned long arg)
> > diff --git a/drivers/s390/crypto/vfio_ap_private.h 
> > b/drivers/s390/crypto/vfio_ap_private.h
> > index 76b7f98e47e9..e8457aa61976 100644
> > --- a/drivers/s390/crypto/vfio_ap_private.h
> > +++ b/drivers/s390/crypto/vfio_ap_private.h
> > @@ -72,6 +72,7 @@ struct ap_matrix {
> >    * @list:    allows the ap_matrix_mdev struct to be added to a list
> >    * @matrix:    the adapters, usage domains and control domains 
> > assigned to the
> >    *        mediated matrix device.
> > + * @shadow_crycb: a shadow copy of the crycb in use by a guest
> >    * @group_notifier: notifier block used for specifying callback 
> > function for
> >    *            handling the VFIO_GROUP_NOTIFY_SET_KVM event
> >    * @kvm:    the struct holding guest's state
> > @@ -79,6 +80,7 @@ struct ap_matrix {
> >   struct ap_matrix_mdev {
> >       struct list_head node;
> >       struct ap_matrix matrix;
> > +    struct ap_matrix *shadow_crycb;
> >       struct notifier_block group_notifier;
> >       struct kvm *kvm;
> >   };