Re: [PATCH v2 6/7] s390: vfio-ap: handle bind and unbind of AP queue device

Pierre Morel
2019-05-06T10:55:49Z

On 03/05/2019 23:14, Tony Krowiak wrote:
> There is nothing preventing a root user from inadvertently unbinding an
> AP queue device that is in use by a guest from the vfio_ap device driver
> and binding it to a zcrypt driver. This can result in a queue being
> accessible from both the host and a guest.
>
> This patch introduces safeguards that prevent sharing of an AP queue
> between the host when a queue device is unbound from the vfio_ap device
> driver. In addition, this patch restores guest access to AP queue devices
> bound to the vfio_ap driver if the queue's APQN is assigned to an mdev
> device in use by a guest.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
> drivers/s390/crypto/vfio_ap_drv.c | 12 +++-
> drivers/s390/crypto/vfio_ap_ops.c | 100 +++++++++++++++++++++++++++++++++-
> drivers/s390/crypto/vfio_ap_private.h | 2 +
> 3 files changed, 111 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
> index e9824c35c34f..c215978daf39 100644
> --- a/drivers/s390/crypto/vfio_ap_drv.c
> +++ b/drivers/s390/crypto/vfio_ap_drv.c
> @@ -42,12 +42,22 @@ MODULE_DEVICE_TABLE(vfio_ap, ap_queue_ids);
>
> static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
> {
> + struct ap_queue *queue = to_ap_queue(&apdev->device);
> +
> + mutex_lock(&matrix_dev->lock);
> + vfio_ap_mdev_probe_queue(queue);
> + mutex_unlock(&matrix_dev->lock);
> +
> return 0;
> }
>
> static void vfio_ap_queue_dev_remove(struct ap_device *apdev)
> {
> - /* Nothing to do yet */
> + struct ap_queue *queue = to_ap_queue(&apdev->device);
> +
> + mutex_lock(&matrix_dev->lock);
> + vfio_ap_mdev_remove_queue(queue);
> + mutex_unlock(&matrix_dev->lock);
> }
>
> static void vfio_ap_matrix_dev_release(struct device *dev)
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index ede45184eb67..40324951bd37 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -226,8 +226,6 @@ static struct device *vfio_ap_get_queue_dev(unsigned long apid,
> &apqn, match_apqn);
> }
>
> -
> -
> static int vfio_ap_mdev_validate_masks(unsigned long *apm, unsigned long *aqm)
> {
> int ret;
> @@ -259,6 +257,27 @@ static bool vfio_ap_queues_on_drv(unsigned long *apm, unsigned long *aqm)
> return true;
> }
>
> +static bool vfio_ap_card_on_drv(struct ap_queue *queue, unsigned long *aqm)
> +{
> + unsigned long apid, apqi;
> + struct device *dev;
> +
> + apid = AP_QID_CARD(queue->qid);
> +
> + for_each_set_bit_inv(apqi, aqm, AP_DOMAINS) {
> + if (queue->qid == AP_MKQID(apid, apqi))
> + continue;
> +
> + dev = vfio_ap_get_queue_dev(apid, apqi);
> + if (!dev)
> + return false;
> +
> + put_device(dev);
> + }
> +
> + return true;
> +}
> +
> /**
> * assign_adapter_store
> *
> @@ -1017,3 +1036,80 @@ void vfio_ap_mdev_unregister(void)
> {
> mdev_unregister_device(&matrix_dev->device);
> }
> +
> +static struct ap_matrix_mdev *vfio_ap_mdev_find_matrix_mdev(unsigned long apid,
> + unsigned long apqi)
> +{
> + struct ap_matrix_mdev *matrix_mdev;
> +
> + list_for_each_entry(matrix_mdev, &matrix_dev->mdev_list, node) {
> + if (test_bit_inv(apid, matrix_mdev->matrix.apm) &&
> + test_bit_inv(apqi, matrix_mdev->matrix.aqm))
> + return matrix_mdev;
> + }
> +
> + return NULL;
> +}
> +
> +void vfio_ap_mdev_probe_queue(struct ap_queue *queue)
> +{
> + struct ap_matrix_mdev *matrix_mdev;
> + unsigned long *shadow_apm, *shadow_aqm;
> + unsigned long apid = AP_QID_CARD(queue->qid);
> + unsigned long apqi = AP_QID_QUEUE(queue->qid);
> +
> + /*
> + * Find the mdev device to which the APQN of the queue device being
> + * probed is assigned
> + */
> + matrix_mdev = vfio_ap_mdev_find_matrix_mdev(apid, apqi);
> +
> + /* Check whether we found an mdev device and it is in use by a guest */
> + if (matrix_mdev && matrix_mdev->kvm) {
> + shadow_apm = matrix_mdev->shadow_crycb->apm;
> + shadow_aqm = matrix_mdev->shadow_crycb->aqm;
> + /*
> + * If the guest already has access to the adapter card
> + * referenced by APID or does not have access to the queues
> + * referenced by APQI, there is nothing to do here.
> + */
> + if (test_bit_inv(apid, shadow_apm) ||
> + !test_bit_inv(apqi, shadow_aqm))
> + return;
> +
> + /*
> + * If each APQN with the APID of the queue being probed and an
> + * APQI in the shadow CRYCB references a queue device that is
> + * bound to the vfio_ap driver, then plug the adapter into the
> + * guest.
> + */
> + if (vfio_ap_card_on_drv(queue, shadow_aqm)) {
> + set_bit_inv(apid, shadow_apm);
> + vfio_ap_mdev_update_crycb(matrix_mdev);
> + }
> + }
> +}
> +
> +void vfio_ap_mdev_remove_queue(struct ap_queue *queue)
> +{
> + struct ap_matrix_mdev *matrix_mdev;
> + unsigned long apid = AP_QID_CARD(queue->qid);
> + unsigned long apqi = AP_QID_QUEUE(queue->qid);
> +
> + matrix_mdev = vfio_ap_mdev_find_matrix_mdev(apid, apqi);
> +
> + /*
> + * If the queue is assigned to the mdev device and the mdev device
> + * is in use by a guest, unplug the adapter referred to by the APID
> + * of the APQN of the queue being removed.
> + */
> + if (matrix_mdev && matrix_mdev->kvm) {
> + if (!test_bit_inv(apid, matrix_mdev->shadow_crycb->apm))
> + return;
> +
> + clear_bit_inv(apid, matrix_mdev->shadow_crycb->apm);
> + vfio_ap_mdev_update_crycb(matrix_mdev);
> + }
> +
> + vfio_ap_mdev_reset_queue(apid, apqi);
> +}
> diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
> index e8457aa61976..6b1f7df5b979 100644
> --- a/drivers/s390/crypto/vfio_ap_private.h
> +++ b/drivers/s390/crypto/vfio_ap_private.h
> @@ -87,5 +87,7 @@ struct ap_matrix_mdev {
>
> extern int vfio_ap_mdev_register(void);
> extern void vfio_ap_mdev_unregister(void);
> +void vfio_ap_mdev_remove_queue(struct ap_queue *queue);
> +void vfio_ap_mdev_probe_queue(struct ap_queue *queue);
>
> #endif /* _VFIO_AP_PRIVATE_H_ */
>

AFAIU the apmask/aqmask of the AP_BUS are replacing bind/unbind for the
admin. Don't they?
Then why not suppress bind/unbind for ap_queues?

Otherwise, it seems to me to handle correctly the disappearance of a
card, which is the only thing that can happen from out of the firmware
queue change requires configuration change and re-IPL.

Even still need testing, LGTM

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