Re: [PATCH v2 3/8] s390: vfio-ap: allow assignment of unavailable AP resources to mdev device

Pierre Morel
2019-04-23T12:46:53Z

On 20/04/2019 23:49, Tony Krowiak wrote:
> The AP architecture does not preclude assignment of AP resources that are
> not yet in the AP configuration (i.e., not available or not online).
> Let's go ahead and implement this facet of the AP architecture for linux
> guests.
>
> Access to AP resources is controlled by bit masks in a guest's SIE
> state description (i.e., the control block containing the state of a
> guest). When an AP instruction is executed on the guest, the firmware
> combines the masks from the guest's SIE state description with the masks
> from the host by doing a logical bitwise AND of the masks to create what
> are defined as effective masks. The effective masks determine which AP
> resources can be accessed by the guest.
>
> Effective masking allows the assignment of AP resources to a guest even
> if the underlying device is not in the AP configuration. If the device
> subsequently becomes configured, the guest will automatically have access
> to the associated AP resources (e.g., AP queues).
>
> The current implementation does not allow assignment of AP resources to
> an mdev device if the AP queues identified by the assignment are not
> bound to the vfio_ap device driver. This patch allows assignment of AP
> resources to the mdev device even if the AP queues are not bound to the
> vfio_ap device driver, as long as the AP queues are not reserved by the
> AP BUS for use by the zcrypt device drivers. If the queues are subsequently
> bound to the vfio_ap device driver while a running guest is using the mdev
> device, the guest will automatically gain access to the queues. Effective
> masking prevents access to queues until such time as they become available.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
> drivers/s390/crypto/vfio_ap_ops.c | 160 +++++---------------------------------
> 1 file changed, 18 insertions(+), 142 deletions(-)
>
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index eae4ee24460a..221491a9ba95 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -113,122 +113,6 @@ static struct attribute_group *vfio_ap_mdev_type_groups[] = {
> NULL,
> };
>
> -struct vfio_ap_queue_reserved {
> - unsigned long *apid;
> - unsigned long *apqi;
> - bool reserved;
> -};
> -
> -/**
> - * vfio_ap_has_queue
> - *
> - * @dev: an AP queue device
> - * @data: a struct vfio_ap_queue_reserved reference
> - *
> - * Flags whether the AP queue device (@dev) has a queue ID containing the APQN,
> - * apid or apqi specified in @data:
> - *
> - * - If @data contains both an apid and apqi value, then @data will be flagged
> - * as reserved if the APID and APQI fields for the AP queue device matches
> - *
> - * - If @data contains only an apid value, @data will be flagged as
> - * reserved if the APID field in the AP queue device matches
> - *
> - * - If @data contains only an apqi value, @data will be flagged as
> - * reserved if the APQI field in the AP queue device matches
> - *
> - * Returns 0 to indicate the input to function succeeded. Returns -EINVAL if
> - * @data does not contain either an apid or apqi.
> - */
> -static int vfio_ap_has_queue(struct device *dev, void *data)
> -{
> - struct vfio_ap_queue_reserved *qres = data;
> - struct ap_queue *ap_queue = to_ap_queue(dev);
> - ap_qid_t qid;
> - unsigned long id;
> -
> - if (qres->apid && qres->apqi) {
> - qid = AP_MKQID(*qres->apid, *qres->apqi);
> - if (qid == ap_queue->qid)
> - qres->reserved = true;
> - } else if (qres->apid && !qres->apqi) {
> - id = AP_QID_CARD(ap_queue->qid);
> - if (id == *qres->apid)
> - qres->reserved = true;
> - } else if (!qres->apid && qres->apqi) {
> - id = AP_QID_QUEUE(ap_queue->qid);
> - if (id == *qres->apqi)
> - qres->reserved = true;
> - } else {
> - return -EINVAL;
> - }
> -
> - return 0;
> -}
> -
> -/**
> - * vfio_ap_verify_queue_reserved
> - *
> - * @matrix_dev: a mediated matrix device
> - * @apid: an AP adapter ID
> - * @apqi: an AP queue index
> - *
> - * Verifies that the AP queue with @apid/@apqi is reserved by the VFIO AP device
> - * driver according to the following rules:
> - *
> - * - If both @apid and @apqi are not NULL, then there must be an AP queue
> - * device bound to the vfio_ap driver with the APQN identified by @apid and
> - * @apqi
> - *
> - * - If only @apid is not NULL, then there must be an AP queue device bound
> - * to the vfio_ap driver with an APQN containing @apid
> - *
> - * - If only @apqi is not NULL, then there must be an AP queue device bound
> - * to the vfio_ap driver with an APQN containing @apqi
> - *
> - * Returns 0 if the AP queue is reserved; otherwise, returns -EADDRNOTAVAIL.
> - */
> -static int vfio_ap_verify_queue_reserved(unsigned long *apid,
> - unsigned long *apqi)
> -{
> - int ret;
> - struct vfio_ap_queue_reserved qres;
> -
> - qres.apid = apid;
> - qres.apqi = apqi;
> - qres.reserved = false;
> -
> - ret = driver_for_each_device(&matrix_dev->vfio_ap_drv->driver, NULL,
> - &qres, vfio_ap_has_queue);
> - if (ret)
> - return ret;
> -
> - if (qres.reserved)
> - return 0;
> -
> - return -EADDRNOTAVAIL;
> -}
> -
> -static int
> -vfio_ap_mdev_verify_queues_reserved_for_apid(struct ap_matrix_mdev *matrix_mdev,
> - unsigned long apid)

You suppress this function but it is still in use in assign_adapter_store...

> -{
> - int ret;
> - unsigned long apqi;
> - unsigned long nbits = matrix_mdev->matrix.aqm_max + 1;
> -
> - if (find_first_bit_inv(matrix_mdev->matrix.aqm, nbits) >= nbits)
> - return vfio_ap_verify_queue_reserved(&apid, NULL);
> -
> - for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm, nbits) {
> - ret = vfio_ap_verify_queue_reserved(&apid, &apqi);
> - if (ret)
> - return ret;
> - }
> -
> - return 0;
> -}
> -
> /**
> * vfio_ap_mdev_verify_no_sharing
> *
> @@ -359,9 +243,17 @@ static ssize_t assign_adapter_store(struct device *dev,
>
> set_bit_inv(apid, matrix_mdev->matrix.apm);
>
> + 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 */
> + ret = (ret == 1) ? -EADDRNOTAVAIL : ret;
> + if (ret)
> + goto error;
> +
> ret = vfio_ap_mdev_verify_no_sharing(matrix_mdev);
> if (ret)
> - goto share_err;
> + goto error;
>
> if (matrix_mdev->shadow_crycb)
> set_bit_inv(apid, matrix_mdev->shadow_crycb->apm);
> @@ -369,7 +261,7 @@ static ssize_t assign_adapter_store(struct device *dev,
> ret = count;
> goto done;
>
> -share_err:
> +error:
> clear_bit_inv(apid, matrix_mdev->matrix.apm);
> done:
> mutex_unlock(&matrix_dev->lock);
> @@ -426,26 +318,6 @@ static ssize_t unassign_adapter_store(struct device *dev,
> }
> static DEVICE_ATTR_WO(unassign_adapter);
>
> -static int
> -vfio_ap_mdev_verify_queues_reserved_for_apqi(struct ap_matrix_mdev *matrix_mdev,
> - unsigned long apqi)
> -{
> - int ret;
> - unsigned long apid;
> - unsigned long nbits = matrix_mdev->matrix.apm_max + 1;
> -
> - if (find_first_bit_inv(matrix_mdev->matrix.apm, nbits) >= nbits)
> - return vfio_ap_verify_queue_reserved(NULL, &apqi);
> -
> - for_each_set_bit_inv(apid, matrix_mdev->matrix.apm, nbits) {
> - ret = vfio_ap_verify_queue_reserved(&apid, &apqi);
> - if (ret)
> - return ret;
> - }
> -
> - return 0;
> -}
> -
> /**
> * assign_domain_store
> *
> @@ -500,12 +372,16 @@ static ssize_t assign_domain_store(struct device *dev,
>
> mutex_lock(&matrix_dev->lock);
>
> - ret = vfio_ap_mdev_verify_queues_reserved_for_apqi(matrix_mdev, apqi);
> - if (ret)
> - goto done;
> -
> set_bit_inv(apqi, matrix_mdev->matrix.aqm);
>
> + 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 */
> + ret = (ret == 1) ? -EADDRNOTAVAIL : ret;
> + if (ret)
> + goto error;

forget to add the error label ?

> +
> ret = vfio_ap_mdev_verify_no_sharing(matrix_mdev);
> if (ret)
> goto share_err;
>

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