Re: [PATCH v4 6/7] s390: ap: Cleanup on removing the AP device

[Pierre Morel]

On 12/03/2019 22:53, Tony Krowiak wrote:
> On 3/11/19 4:31 AM, Pierre Morel wrote:
> > On 08/03/2019 23:43, Tony Krowiak wrote:
> > > On 2/22/19 10:29 AM, Pierre Morel wrote:
> > > > When the device is remove, we must make sure to
> > > > clear the interruption and reset the AP device.
> > > >
> > > > We also need to clear the CRYCB of the guest.
> > > >
> > > > Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
> > > > ---
> > > > Â drivers/s390/crypto/vfio_ap_drv.cÂÂÂÂ | 35 
> > > > +++++++++++++++++++++++++++++++++++
> > > > Â drivers/s390/crypto/vfio_ap_ops.cÂÂÂÂ |Â 3 ++-
> > > > Â drivers/s390/crypto/vfio_ap_private.h |Â 3 +++
> > > > Â 3 files changed, 40 insertions(+), 1 deletion(-)

...snip...

> > > > + * vfio_ap_update_crycb
> > > > + * @q: A pointer to the queue being removed
> > > > + *
> > > > + * We clear the APID of the queue, making this queue unusable for 
> > > > the guest.
> > > > + * After this function we can reset the queue without to fear a 
> > > > race with
> > > > + * the guest to access the queue again.
> > > > + * We do not fear race with the host as we still get the devic
> > > > + */
> > > > +static void vfio_ap_update_crycb(struct vfio_ap_queue *q)
> > > > +{
> > > > +ÂÂÂ struct ap_matrix_mdev *matrix_mdev = q->matrix_mdev;
> > > > +
> > > > +ÂÂÂ if (!matrix_mdev)
> > > > +ÂÂÂÂÂÂÂ return;
> > > > +
>
> You should probably check whether the APID has been cleared before
> proceeding. Take the case where an AP with multiple queues is removed
> from the configuration via the SE or SCLP. The AP bus is going to invoke
> the vfio_ap_queue_dev_remove() function for each of the queues. The APID
> will get cleared on the first remove, so it is not only unnecessary to
> clear it on subsequent removes, it is kind of nasty to keep resetting
> the masks in the guest's CRYCB (below) each time the remove callback is
> invoked.

This can not happen.
The only way to clear the APM is when the matrix is not associated with KVM.

This case is tested and the masks are not changed.

> > > > +ÂÂÂ clear_bit_inv(AP_QID_CARD(q->apqn), matrix_mdev->matrix.apm);
> > > > +
> > > > +ÂÂÂ if (!matrix_mdev->kvm)
> > > > +ÂÂÂÂÂÂÂ return;
> > > > +
> > > > +ÂÂÂ kvm_arch_crypto_set_masks(matrix_mdev->kvm,
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ matrix_mdev->matrix.apm,
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ matrix_mdev->matrix.aqm,
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ matrix_mdev->matrix.adm);
> > > > +}




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