Re: [PATCH] s390/vfio-ap: Clean up vfio_ap resources when KVM pointer invalidated

[Tony Krowiak]

On 12/4/20 11:57 AM, Cornelia Huck wrote:
> On Fri, 4 Dec 2020 11:48:24 -0500
> Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote:
>
> > On 12/3/20 12:55 PM, Halil Pasic wrote:
> > > On Wed,  2 Dec 2020 18:41:01 -0500
> > > Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote:
> > >   
> > > > The vfio_ap device driver registers a group notifier with VFIO when the
> > > > file descriptor for a VFIO mediated device for a KVM guest is opened to
> > > > receive notification that the KVM pointer is set (VFIO_GROUP_NOTIFY_SET_KVM
> > > > event). When the KVM pointer is set, the vfio_ap driver stashes the pointer
> > > > and calls the kvm_get_kvm() function to increment its reference counter.
> > > > When the notifier is called to make notification that the KVM pointer has
> > > > been set to NULL, the driver should clean up any resources associated with
> > > > the KVM pointer and decrement its reference counter. The current
> > > > implementation does not take care of this clean up.
> > > >
> > > > Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> > > Do we need a Fixes tag? Do we need this backported? In my opinion
> > > this is necessary since the interrupt patches.
> > I'll put in a fixes tag:
> > Fixes: 258287c994de (s390: vfio-ap: implement mediated device open callback)
> The canonical format would be
>
> Fixes: 258287c994de ("s390: vfio-ap: implement mediated device open callback")

Okay.

> > Yes, this should probably be backported.
> >
> > >   
> > > > ---
> > > >    drivers/s390/crypto/vfio_ap_ops.c | 21 +++++++++++++--------
> > > >    1 file changed, 13 insertions(+), 8 deletions(-)
> > > >
> > > > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> > > > index e0bde8518745..eeb9c9130756 100644
> > > > --- a/drivers/s390/crypto/vfio_ap_ops.c
> > > > +++ b/drivers/s390/crypto/vfio_ap_ops.c
> > > > @@ -1083,6 +1083,17 @@ static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb,
> > > >    	return NOTIFY_DONE;
> > > >    }
> > > >    
> > > > +static void vfio_ap_mdev_put_kvm(struct ap_matrix_mdev *matrix_mdev)
> > > I don't like the name. The function does more that put_kvm. Maybe
> > > something  like _disconnect_kvm()?
> > Since the vfio_ap_mdev_set_kvm() function is called by the
> > notifier when the KVM pointer is set, how about:
> >
> > vfio_ap_mdev_unset_kvm()
> >
> > for when the KVM pointer is nullified?
> Sounds good to me.