Re: [PATCH v9 02/15] s390/vfio-ap: use new AP bus interface to search for queue devices

[Pierre Morel]

On 2020-07-20 17:03, 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.

The patch does much more than modifying this line. ;)

> Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> ---
>   drivers/s390/crypto/vfio_ap_drv.c     | 27 ++-------
>   drivers/s390/crypto/vfio_ap_ops.c     | 86 +++++++++++++++------------
>   drivers/s390/crypto/vfio_ap_private.h |  8 ++-
>   3 files changed, 59 insertions(+), 62 deletions(-)
>
> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
> index f4ceb380dd61..24cdef60039a 100644
> --- a/drivers/s390/crypto/vfio_ap_drv.c
> +++ b/drivers/s390/crypto/vfio_ap_drv.c
> @@ -53,15 +53,9 @@ 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);
>   }

You should explain the reason why this function is modified.

>   
>   /**
> @@ -72,18 +66,9 @@ static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
>    */
>   static void vfio_ap_queue_dev_remove(struct ap_device *apdev)
>   {
> -	struct vfio_ap_queue *q;
> -	int apid, apqi;
> -
> -	mutex_lock(&matrix_dev->lock);
> -	q = dev_get_drvdata(&apdev->device);
> -	dev_set_drvdata(&apdev->device, NULL);
> -	apid = AP_QID_CARD(q->apqn);
> -	apqi = AP_QID_QUEUE(q->apqn);
> -	vfio_ap_mdev_reset_queue(apid, apqi, 1);
> -	vfio_ap_irq_disable(q);
> -	kfree(q);
> -	mutex_unlock(&matrix_dev->lock);
> +	struct ap_queue *queue = to_ap_queue(&apdev->device);
> +
> +	vfio_ap_mdev_remove_queue(queue);
>   }

... and this one?

>   
>   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 e0bde8518745..ad3925f04f61 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -26,43 +26,26 @@
>   
>   static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev);
>   
> -static int match_apqn(struct device *dev, const void *data)
> -{
> -	struct vfio_ap_queue *q = dev_get_drvdata(dev);
> -
> -	return (q->apqn == *(int *)(data)) ? 1 : 0;
> -}
> -
>   /**
> - * vfio_ap_get_queue: Retrieve a queue with a specific APQN from a list
> - * @matrix_mdev: the associated mediated matrix
> + * vfio_ap_get_queue: Retrieve a queue with a specific APQN.
>    * @apqn: The queue APQN
>    *
> - * Retrieve a queue with a specific APQN from the list of the
> - * devices of the vfio_ap_drv.
> - * Verify that the APID and the APQI are set in the matrix.
> + * Retrieve a queue with a specific APQN from the AP queue devices attached to
> + * the AP bus.
>    *
> - * Returns the pointer to the associated vfio_ap_queue
> + * Returns the pointer to the vfio_ap_queue with the specified APQN, or NULL.
>    */
> -static struct vfio_ap_queue *vfio_ap_get_queue(
> -					struct ap_matrix_mdev *matrix_mdev,
> -					int apqn)
> +static struct vfio_ap_queue *vfio_ap_get_queue(unsigned long apqn)
>   {
> +	struct ap_queue *queue;
>   	struct vfio_ap_queue *q;
> -	struct device *dev;
>   
> -	if (!test_bit_inv(AP_QID_CARD(apqn), matrix_mdev->matrix.apm))
> -		return NULL;
> -	if (!test_bit_inv(AP_QID_QUEUE(apqn), matrix_mdev->matrix.aqm))
> +	queue = ap_get_qdev(apqn);
> +	if (!queue)
>   		return NULL;
>   
> -	dev = driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL,
> -				 &apqn, match_apqn);
> -	if (!dev)
> -		return NULL;
> -	q = dev_get_drvdata(dev);
> -	q->matrix_mdev = matrix_mdev;
> -	put_device(dev);
> +	q = dev_get_drvdata(&queue->ap_dev.device);
> +	put_device(&queue->ap_dev.device);
>   
>   	return q;
>   }

this function changed a lot too, you should explain the goal in the 
patch comment.

...snip...

Regards,
Pierre

--
Pierre Morel
IBM Lab Boeblingen