Re: [PATCH v2 7/8] s390: vfio-ap: handle bind and unbind of AP queue device

Pierre Morel
2019-04-23T13:08:36Z

On 20/04/2019 23:49, Tony Krowiak wrote:
> There is an implied guarantee that when an AP queue device is bound to a
> device driver, that driver will have exclusive control over the device.
> When an AP queue device is unbound from the vfio_ap driver while the
> queue is in use by a guest and subsquently bound to a zcrypt driver, the
> guarantee that the zcrypt driver has exclusive control of the queue
> device will be violated. Likewise, when an AP queue device is bound to
> the vfio_ap device driver and its APQN is assigned to an mdev device in
> use by a guest, the expectation is that the guest will have access to
> the queue.
>
> The purpose of this patch is to ensure three things:
>
> 1. When an AP queue device in use by a guest is unbound, the guest shall
> no longer access the queue. Due to the limitations of the
> architecture, access to a single queue can not be denied to a guest,
> so access to the AP card to which the queue is connected will be
> denied to the guest.
>
> 2. When an AP queue device with an APQN assigned to an mdev device is
> bound to the vfio_ap driver while the mdev device is in use by a guest,
> the guest shall be granted access to the queue.
>
> 3. When a guest is started, each APQN assigned to the guest's mdev device
> must be owned by the vfio_ap driver.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
> drivers/s390/crypto/vfio_ap_drv.c | 16 ++++++-
> drivers/s390/crypto/vfio_ap_ops.c | 82 ++++++++++++++++++++++++++++++++++-
> drivers/s390/crypto/vfio_ap_private.h | 2 +
> 3 files changed, 97 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
> index e9824c35c34f..0f5dafddf5b1 100644
> --- a/drivers/s390/crypto/vfio_ap_drv.c
> +++ b/drivers/s390/crypto/vfio_ap_drv.c
> @@ -42,12 +42,26 @@ MODULE_DEVICE_TABLE(vfio_ap, ap_queue_ids);
>
> static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
> {
> + struct ap_queue *apq = to_ap_queue(&apdev->device);
> + unsigned long apid = AP_QID_CARD(apq->qid);
> + unsigned long apqi = AP_QID_QUEUE(apq->qid);
> +
> + mutex_lock(&matrix_dev->lock);
> + vfio_ap_mdev_probe_queue(apid, apqi);
> + 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 *apq = to_ap_queue(&apdev->device);
> + unsigned long apid = AP_QID_CARD(apq->qid);
> + unsigned long apqi = AP_QID_QUEUE(apq->qid);
> +
> + mutex_lock(&matrix_dev->lock);
> + vfio_ap_mdev_remove_queue(apid, apqi);
> + 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 31ce30ee784d..3f9506516545 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -763,8 +763,8 @@ static void vfio_ap_mdev_wait_for_qempty(unsigned long apid, unsigned long apqi)
> msleep(20);
> break;
> default:
> - pr_warn("%s: tapq err %02x: 0x%04x may not be empty\n",
> - __func__, status.response_code, q->apqn);
> + pr_warn("%s: tapq err %02x: %02lx%04lx may not be empty\n",
> + __func__, status.response_code, apid, apqi);
> return;
> }
> } while (--retry);
> @@ -823,6 +823,14 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
>
> static int vfio_ap_mdev_create_shadow_crycb(struct ap_matrix_mdev *matrix_mdev)
> {
> + /*
> + * If an AP resource is not owned by the vfio_ap driver - e.g., it was
> + * unbound from the driver while still assigned to the mdev device
> + */
> + if (ap_apqn_in_matrix_owned_by_def_drv(matrix_mdev->matrix.apm,
> + matrix_mdev->matrix.aqm))
> + return -EADDRNOTAVAIL;
> +
> matrix_mdev->shadow_crycb = kzalloc(sizeof(*matrix_mdev->shadow_crycb),
> GFP_KERNEL);
> if (!matrix_mdev->shadow_crycb)
> @@ -847,6 +855,18 @@ static int vfio_ap_mdev_open(struct mdev_device *mdev)
> if (!try_module_get(THIS_MODULE))
> return -ENODEV;
>
> + ret = ap_apqn_in_matrix_owned_by_def_drv(matrix_mdev->matrix.apm,
> + matrix_mdev->matrix.aqm);
> +
> + /*
> + * If any APQN is owned by a default driver, it can not be used by the
> + * guest. This can happen if a queue is unbound from the vfio_ap
> + * driver but not unassigned from the mdev device.
> + */
> + ret = (ret == 1) ? -EADDRNOTAVAIL : ret;
> + if (ret)
> + return ret;
> +
> matrix_mdev->group_notifier.notifier_call = vfio_ap_mdev_group_notifier;
> events = VFIO_GROUP_NOTIFY_SET_KVM;
>
> @@ -938,3 +958,61 @@ 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_remove_queue(unsigned long apid, unsigned long apqi)
> +{
> + struct ap_matrix_mdev *matrix_mdev;
> +
> + 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
> + */
> + if (matrix_mdev && matrix_mdev->kvm) {
> + /*
> + * Unplug the adapter from the guest but don't unassign it
> + * from the mdev device
> + */
> + clear_bit_inv(apid, matrix_mdev->shadow_crycb->apm);
> + vfio_ap_mdev_update_crycb(matrix_mdev);
> + }
> +
> + vfio_ap_mdev_reset_queue(apid, apqi);
> +}
> +
> +void vfio_ap_mdev_probe_queue(unsigned long apid, unsigned long apqi)
> +{
> + struct ap_matrix_mdev *matrix_mdev;
> +
> + 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
> + */
> + if (matrix_mdev && matrix_mdev->kvm) {
> + /* Plug the adapter into the guest */
> + set_bit_inv(apid, matrix_mdev->shadow_crycb->apm);
> +
> + /* Make sure the queue is also plugged in to the guest */
> + if (!test_bit_inv(apqi, matrix_mdev->shadow_crycb->aqm))
> + set_bit_inv(apqi, matrix_mdev->shadow_crycb->aqm);

Why are you testing the domain before setting it and not the adapter?

Eventually you do not need to test at all or if, then both.

NIT

> +
> + vfio_ap_mdev_update_crycb(matrix_mdev);
> + }
> +}
> diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
> index e8457aa61976..00eaae3b853f 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(unsigned long apid, unsigned long apqi);
> +void vfio_ap_mdev_probe_queue(unsigned long apid, unsigned long apqi);
>
> #endif /* _VFIO_AP_PRIVATE_H_ */
>

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