linux-kernel - Re: [PATCH] s390: vfio-ap: remove unnecessary calls to disable queue interrupts

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Message-ID: <20190813132957.7fafad2d.cohuck@redhat.com>
Date:   Tue, 13 Aug 2019 13:29:57 +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,
        frankja@...ux.ibm.com, david@...hat.com, mjrosato@...ux.ibm.com,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        pmorel@...ux.ibm.com, pasic@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com
Subject: Re: [PATCH] s390: vfio-ap: remove unnecessary calls to disable
 queue interrupts

On Mon, 12 Aug 2019 16:47:09 -0400
Tony Krowiak <akrowiak@...ux.ibm.com> wrote:

> When an AP queue is reset (zeroized), interrupts are disabled. The queue
> reset function currently tries to disable interrupts unnecessarily. This patch
> removes the unnecessary calls to disable interrupts after queue reset.
> 
> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
> ---
>  drivers/s390/crypto/vfio_ap_ops.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 0604b49a4d32..407c2f0f25f9 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -1114,18 +1114,19 @@ static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
>  	return NOTIFY_OK;
>  }
>  
> -static void vfio_ap_irq_disable_apqn(int apqn)
> +static struct vfio_ap_queue *vfio_ap_find_qdev(int apqn)
>  {
>  	struct device *dev;
> -	struct vfio_ap_queue *q;
> +	struct vfio_ap_queue *q = NULL;
>  
>  	dev = driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL,
>  				 &apqn, match_apqn);
>  	if (dev) {
>  		q = dev_get_drvdata(dev);
> -		vfio_ap_irq_disable(q);
>  		put_device(dev);
>  	}
> +
> +	return q;
>  }
>  
>  int vfio_ap_mdev_reset_queue(unsigned int apid, unsigned int apqi,
> @@ -1164,6 +1165,7 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
>  	int rc = 0;
>  	unsigned long apid, apqi;
>  	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> +	struct vfio_ap_queue *q;
>  
>  	for_each_set_bit_inv(apid, matrix_mdev->matrix.apm,
>  			     matrix_mdev->matrix.apm_max + 1) {
> @@ -1177,7 +1179,10 @@ static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev)
>  			 */
>  			if (ret)
>  				rc = ret;
> -			vfio_ap_irq_disable_apqn(AP_MKQID(apid, apqi));

Might be useful to stick a comment in this function that resetting the
queue has also disabled the interrupts, as the architecture
documentation for that is not publicly available.

> +
> +			q = vfio_ap_find_qdev(AP_MKQID(apid, apqi));
> +			if (q)
> +				vfio_ap_free_aqic_resources(q);
>  		}
>  	}
>  

Trusting your reading of the architecture,
Reviewed-by: Cornelia Huck <cohuck@...hat.com>