Re: [PATCH v6 3/7] s390: ap: setup relation betwen KVM and mediated device

[Pierre Morel <pmorel@xxxxxxxxxxxxx>]

On 28/03/2019 17:12, Tony Krowiak wrote:
> On 3/22/19 10:43 AM, Pierre Morel wrote:
> > When the mediated device is open we setup the relation with KVM unset it
> > when the mediated device is released.
>
> s/open we setup/open, we set up/
> s/with KVM unset/with KVM and unset/
>
> > We lock the matrix mediated device to avoid any change until the
> > open is done.
> > We make sure that KVM is present when opening the mediated device
> > otherwise we return an error.
>
> s/mediated device/mediated device,/
>
> > Increase kvm's refcount to ensure the KVM structures are still available
> > during the use of the mediated device by the guest.
> >
> > Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
> > ---
> >   drivers/s390/crypto/vfio_ap_ops.c | 143 
> > +++++++++++++++++++++-----------------
> >   1 file changed, 79 insertions(+), 64 deletions(-)
> >
> > diff --git a/drivers/s390/crypto/vfio_ap_ops.c 
> > b/drivers/s390/crypto/vfio_ap_ops.c
> > index 77f7bac..bdb36e0 100644
> > --- a/drivers/s390/crypto/vfio_ap_ops.c
> > +++ b/drivers/s390/crypto/vfio_ap_ops.c
> > @@ -787,74 +787,24 @@ static const struct attribute_group 
> > *vfio_ap_mdev_attr_groups[] = {
> >       NULL
> >   };
> > -/**
> > - * vfio_ap_mdev_set_kvm
> > - *
> > - * @matrix_mdev: a mediated matrix device
> > - * @kvm: reference to KVM instance
> > - *
> > - * Verifies no other mediated matrix device has @kvm and sets a 
> > reference to
> > - * it in @matrix_mdev->kvm.
> > - *
> > - * Return 0 if no other mediated matrix device has a reference to @kvm;
> > - * otherwise, returns an -EPERM.
> > - */
> > -static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev,
> > -                struct kvm *kvm)
> > -{
> > -    struct ap_matrix_mdev *m;
> > -
> > -    mutex_lock(&matrix_dev->lock);
> > -
> > -    list_for_each_entry(m, &matrix_dev->mdev_list, node) {
> > -        if ((m != matrix_mdev) && (m->kvm == kvm)) {
> > -            mutex_unlock(&matrix_dev->lock);
> > -            return -EPERM;
> > -        }
> > -    }
> > -
> > -    matrix_mdev->kvm = kvm;
> > -    mutex_unlock(&matrix_dev->lock);
> > -
> > -    return 0;
> > -}
> > -
> >   static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
> >                          unsigned long action, void *data)
> >   {
> > -    int ret;
> >       struct ap_matrix_mdev *matrix_mdev;
> >       if (action != VFIO_GROUP_NOTIFY_SET_KVM)
> >           return NOTIFY_OK;
> >       matrix_mdev = container_of(nb, struct ap_matrix_mdev, 
> > group_notifier);
> > -
> > -    if (!data) {
> > -        matrix_mdev->kvm = NULL;
> > -        return NOTIFY_OK;
> > -    }
> > -
> > -    ret = vfio_ap_mdev_set_kvm(matrix_mdev, data);
> > -    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);
> > +    matrix_mdev->kvm = data;
> >       return NOTIFY_OK;
> >   }
> > -static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
> > +static int vfio_ap_mdev_reset_queues(struct ap_matrix_mdev *matrix_mdev)
> >   {
> >       int ret;
> >       int rc = 0;
> > -    struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> >       struct vfio_ap_queue *q;
> >       list_for_each_entry(q, &matrix_mdev->qlist, list) {
> > @@ -871,41 +821,106 @@ static int vfio_ap_mdev_reset_queues(struct 
> > mdev_device *mdev)
> >       return rc;
> >   }
> > +/**
> > + * vfio_ap_mdev_set_kvm
> > + *
> > + * @matrix_mdev: a mediated matrix device
> > + *
> > + * - Verifies that the hook is free and install the PQAP hook
> > + * - Copy the matrix masks inside the CRYCB
> > + * - Increment the KVM rerference count
> > + *
> > + * Return 0 if no other mediated matrix device has a reference to @kvm;
> > + * otherwise, returns an -EPERM.
> > + */
> > +static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev)
> > +{
> > +    if (matrix_mdev->kvm->arch.crypto.pqap_hook)
> > +        return -EPERM;
>
> How would this happen; in other words, why are we checking this?

I check this to verify that no other AP mediated device is already in 
use by this VM.

Regards,
Pierre



--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany