Re: [PATCH 3/7] s390/vfio_ap: use TAPQ to verify reset in progress completes

From: Harald Freudenberger <freude@linux.ibm.com>
To: Tony Krowiak <akrowiak@linux.ibm.com>
Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, jjherne@linux.ibm.com,
	borntraeger@de.ibm.com, cohuck@redhat.com,
	mjrosato@linux.ibm.com, pasic@linux.ibm.com,
	alex.williamson@redhat.com, kwankhede@nvidia.com,
	fiuczy@linux.ibm.com
Subject: Re: [PATCH 3/7] s390/vfio_ap: use TAPQ to verify reset in progress completes
Date: Thu, 15 Dec 2022 11:51:41 +0100	[thread overview]
Message-ID: <2541e0d3d4fb38af995e8bd91a34986d@linux.ibm.com> (raw)
In-Reply-To: <20221213154437.15480-4-akrowiak@linux.ibm.com>

On 2022-12-13 16:44, Tony Krowiak wrote:
> To eliminate the repeated calls to the PQAP(ZAPQ) function to verify 
> that
> a reset in progress completed successfully and ensure that error 
> response
> codes get appropriately logged, let's call the apq_reset_check() 
> function
> when the ZAPQ response code indicates that a reset that is already in
> progress.
> 
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
>  drivers/s390/crypto/vfio_ap_ops.c | 24 +++++++++++++-----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c
> b/drivers/s390/crypto/vfio_ap_ops.c
> index a5530a46cf31..5bf2d93ae8af 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -33,7 +33,7 @@
>  static int vfio_ap_mdev_reset_queues(struct ap_queue_table *qtable);
>  static struct vfio_ap_queue *vfio_ap_find_queue(int apqn);
>  static const struct vfio_device_ops vfio_ap_matrix_dev_ops;
> -static int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q, unsigned
> int retry);
> +static int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q);
> 
>  /**
>   * get_update_locks_for_kvm: Acquire the locks required to dynamically 
> update a
> @@ -1632,8 +1632,7 @@ static int apq_reset_check(struct vfio_ap_queue 
> *q)
>  	return ret;
>  }
> 
> -static int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q,
> -				    unsigned int retry)
> +static int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q)
>  {
>  	struct ap_queue_status status;
>  	int ret;
> @@ -1648,12 +1647,15 @@ static int vfio_ap_mdev_reset_queue(struct
> vfio_ap_queue *q,
>  		ret = 0;
>  		break;
>  	case AP_RESPONSE_RESET_IN_PROGRESS:
> -		if (retry--) {
> -			msleep(20);
> -			goto retry_zapq;
> -		}
> -		ret = -EBUSY;
> -		break;
> +		/*
> +		 * There is a reset issued by another process in progress. Let's 
> wait
> +		 * for that to complete. Since we have no idea whether it was a RAPQ 
> or
> +		 * ZAPQ, then if it completes successfully, let's issue the ZAPQ.
> +		 */
> +		ret = apq_reset_check(q);
> +		if (ret)
> +			break;
> +		goto retry_zapq;
>  	case AP_RESPONSE_Q_NOT_AVAIL:
>  	case AP_RESPONSE_DECONFIGURED:
>  	case AP_RESPONSE_CHECKSTOPPED:
> @@ -1688,7 +1690,7 @@ static int vfio_ap_mdev_reset_queues(struct
> ap_queue_table *qtable)
>  	struct vfio_ap_queue *q;
> 
>  	hash_for_each(qtable->queues, loop_cursor, q, mdev_qnode) {
> -		ret = vfio_ap_mdev_reset_queue(q, 1);
> +		ret = vfio_ap_mdev_reset_queue(q);
>  		/*
>  		 * Regardless whether a queue turns out to be busy, or
>  		 * is not operational, we need to continue resetting
> @@ -1931,7 +1933,7 @@ void vfio_ap_mdev_remove_queue(struct ap_device 
> *apdev)
>  		}
>  	}
> 
> -	vfio_ap_mdev_reset_queue(q, 1);
> +	vfio_ap_mdev_reset_queue(q);
>  	dev_set_drvdata(&apdev->device, NULL);
>  	kfree(q);
>  	release_update_locks_for_mdev(matrix_mdev);

Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>