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

[Pierre Morel]

On 26/02/2019 19:27, 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(-)
> >
> > diff --git a/drivers/s390/crypto/vfio_ap_drv.c 
> > b/drivers/s390/crypto/vfio_ap_drv.c
> > index eca0ffc..e5d91ff 100644
> > --- a/drivers/s390/crypto/vfio_ap_drv.c
> > +++ b/drivers/s390/crypto/vfio_ap_drv.c
> > @@ -5,6 +5,7 @@
> > ÂÂ * Copyright IBM Corp. 2018
> > ÂÂ *
> > ÂÂ * Author(s): Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> > + *ÂÂÂÂÂÂÂÂÂ Pierre Morel <pmorel@xxxxxxxxxxxxx>
> > ÂÂ */
> > Â #include <linux/module.h>
> > @@ -12,6 +13,8 @@
> > Â #include <linux/slab.h>
> > Â #include <linux/string.h>
> > Â #include <asm/facility.h>
> > +#include <linux/bitops.h>
> > +#include <linux/kvm_host.h>
> > Â #include "vfio_ap_private.h"
> > Â #define VFIO_AP_ROOT_NAME "vfio_ap"
> > @@ -61,6 +64,33 @@ static int vfio_ap_queue_dev_probe(struct ap_device 
> > *apdev)
> > Â }
> > Â /**
> > + * 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 device.
> > + */
> > +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;
> > +
> > +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);
> > +}
> > +
> > +/**
> > ÂÂ * vfio_ap_queue_dev_remove:
> > ÂÂ *
> > ÂÂ * Free the associated vfio_ap_queue structure
> > @@ -70,6 +100,11 @@ static void vfio_ap_queue_dev_remove(struct 
> > ap_device *apdev)
> > ÂÂÂÂÂ struct vfio_ap_queue *q;
> > ÂÂÂÂÂ q = dev_get_drvdata(&apdev->device);
> > +ÂÂÂ if (!q)
> > +ÂÂÂÂÂÂÂ return;
> > +
> > +ÂÂÂ vfio_ap_update_crycb(q);
> > +ÂÂÂ vfio_ap_mdev_reset_queue(q);
>
> The reset is unnecessary because once the card is removed from the
> CRYCB, the ZAPQ may fail with because the queue may not exist anymore.

The code here is run inside the host. So the queue is still available 
for ZAPQ.


> Besides, once the card is removed from the guest's CRYCB, the bus
> running in the guest will do a reset.

I already answered this:
- The AP bus reset the queue before calling the driver probe
- which means that the guest can still access the queue after the reset 
done by the bus.
- we need to first clear the CRYCB to remove the queue from the guest 
before we reset the queue.


Regards,
Pierre


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