Re: [PATCH v3 6/9] vfio: ap: register IOMMU VFIO notifier

Halil Pasic
2019-02-19T09:59:58Z

On Fri, 15 Feb 2019 17:55:35 -0500
Tony Krowiak <akrowiak@linux.ibm.com> wrote:

> On 2/14/19 8:51 AM, Pierre Morel wrote:
> > To be able to use the VFIO interface to facilitate the
> > mediated device memory pining/unpining we need to register
> > a notifier for IOMMU.
> >
> > Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> > ---
> > drivers/s390/crypto/vfio_ap_ops.c | 64 +++++++++++++++++++++++++++++++----
> > drivers/s390/crypto/vfio_ap_private.h | 2 ++
> > 2 files changed, 60 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> > index 1851b24..6eddc2c 100644
> > --- a/drivers/s390/crypto/vfio_ap_ops.c
> > +++ b/drivers/s390/crypto/vfio_ap_ops.c

[..]
struct vfio_ap_queue *q;
> > @@ -967,12 +996,32 @@ static int vfio_ap_mdev_open(struct mdev_device *mdev)
> >
> > ret = vfio_register_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
> > &events, &matrix_mdev->group_notifier);
> > - if (ret) {
> > - module_put(THIS_MODULE);
> > - return ret;
> > - }
> > + if (ret)
> > + goto err_group;
> > +
> > + matrix_mdev->iommu_notifier.notifier_call = vfio_ap_mdev_iommu_notifier;
> > + events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
> > +
> > + ret = vfio_register_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> > + &events, &matrix_mdev->iommu_notifier);
> > + if (ret)
> > + goto err_iommu;
> > +
> > + ret = vfio_ap_associate_queues(matrix_mdev);
> > + if (ret)
> > + goto err_associate;
>
> I think the matrix_mdev should be associated with queues when an
> assignment of an adapter or domain is made to the mdev device via its
> sysfs interfaces. I say this because assigning an adapter or domain to
> an mdev device effectively grants ownership of any additional AP queues
> added to the mdev device's AP matrix as a result of the assignment. It
> only makes sense to assign ownership to the vfio_ap_queue objects
> representing the queues at that time. If an adapter or domain is
> dynamically assigned while a guest is using the affected queues, then
> the associations will have to be made at that time and this code will
> likely go bye bye.
>

Actually, we need the stuff in vfio_ap_queues only if the guest is
offered to decides to use AP adaper interrupts. I would prefer to have
it around only when needed: as long as we have the nib pinned for any
given queue. Is there a reason why not to do so?

Regards,
Halil

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