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

[Pierre Morel <pmorel@linux.ibm.com>]

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