linux-kernel - Re: [PATCH v10 02/16] s390/vfio-ap: use new AP bus interface to search for queue devices

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Date:   Tue, 25 Aug 2020 12:13:34 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ux.ibm.com, borntraeger@...ibm.com,
        mjrosato@...ux.ibm.com, pasic@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com,
        fiuczy@...ux.ibm.com, frankja@...ux.ibm.com, david@...hat.com,
        imbrenda@...ux.ibm.com, hca@...ux.ibm.com, gor@...ux.ibm.com,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v10 02/16] s390/vfio-ap: use new AP bus interface to
 search for queue devices

On Fri, 21 Aug 2020 15:56:02 -0400
Tony Krowiak <akrowiak@...ux.ibm.com> wrote:

> This patch refactor's the vfio_ap device driver to use the AP bus's

s/refactor's/refactors/

> 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@...ux.ibm.com>
> Reported-by: kernel test robot <lkp@...el.com>
> ---
>  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_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))

I think you should add some explanation to the patch description why
testing the matrix bitmasks is not needed anymore.

> +	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;
>  }

(...)