Re: [PATCH v8 02/16] s390/vfio-ap: use new AP bus interface to search for queue devices

Christian Borntraeger
2020-06-16T15:46:09Z

On 05.06.20 23:39, Tony Krowiak wrote:
> This patch refactor's the vfio_ap device driver to use the AP bus's
> ap_get_qdev() function to retrieve the vfio_ap_queue struct containing
> information about a queue that is bound to the vfio_ap device driver.
> The bus's ap_get_qdev() function retrieves the queue device from a
> hashtable keyed by APQN. This is much more efficient than looping over
> the list of devices attached to the AP bus by several orders of
> magnitude.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
> drivers/s390/crypto/vfio_ap_drv.c | 27 ++-------
> drivers/s390/crypto/vfio_ap_ops.c | 82 +++++++++++++++------------
> drivers/s390/crypto/vfio_ap_private.h | 8 ++-
> 3 files changed, 58 insertions(+), 59 deletions(-)
>
> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
> index be2520cc010b..59233cf7419d 100644
> --- a/drivers/s390/crypto/vfio_ap_drv.c
> +++ b/drivers/s390/crypto/vfio_ap_drv.c
> @@ -51,15 +51,9 @@ MODULE_DEVICE_TABLE(vfio_ap, ap_queue_ids);
> */
> static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
> {
> - struct vfio_ap_queue *q;
> -
> - q = kzalloc(sizeof(*q), GFP_KERNEL);
> - if (!q)
> - return -ENOMEM;
> - dev_set_drvdata(&apdev->device, q);
> - q->apqn = to_ap_queue(&apdev->device)->qid;
> - q->saved_isc = VFIO_AP_ISC_INVALID;
> - return 0;
> + struct ap_queue *queue = to_ap_queue(&apdev->device);
> +
> + return vfio_ap_mdev_probe_queue(queue);
> }

Here we did not hold a mutex in the old code
[...]

> +int vfio_ap_mdev_probe_queue(struct ap_queue *queue)
> +{
> + struct vfio_ap_queue *q;
> +
> + q = kzalloc(sizeof(*q), GFP_KERNEL);
> + if (!q)
> + return -ENOMEM;
> +
> + mutex_lock(&matrix_dev->lock);
> + dev_set_drvdata(&queue->ap_dev.device, q);
> + q->apqn = queue->qid;
> + q->saved_isc = VFIO_AP_ISC_INVALID;
> + mutex_unlock(&matrix_dev->lock);
> +

here we do. Why do we need the matrix_dev->lock here?