linux-kernel - Re: [PATCH v5 2/7] s390: ap: new vfio_ap

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Date:   Fri, 15 Mar 2019 11:33:30 +0100
From:   Cornelia Huck <cohuck@...hat.com>
To:     Pierre Morel <pmorel@...ux.ibm.com>
Cc:     borntraeger@...ibm.com, alex.williamson@...hat.com,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, frankja@...ux.ibm.com, akrowiak@...ux.ibm.com,
        pasic@...ux.ibm.com, david@...hat.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, freude@...ux.ibm.com, mimu@...ux.ibm.com
Subject: Re: [PATCH v5 2/7] s390: ap: new vfio_ap_queue structure

On Wed, 13 Mar 2019 17:04:59 +0100
Pierre Morel <pmorel@...ux.ibm.com> wrote:

> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
> index e9824c3..df6f21a 100644
> --- a/drivers/s390/crypto/vfio_ap_drv.c
> +++ b/drivers/s390/crypto/vfio_ap_drv.c
> @@ -40,14 +40,42 @@ static struct ap_device_id ap_queue_ids[] = {
>  
>  MODULE_DEVICE_TABLE(vfio_ap, ap_queue_ids);
>  
> +/**
> + * vfio_ap_queue_dev_probe:
> + *
> + * Allocate a vfio_ap_queue structure and associate it
> + * with the device as driver_data.
> + */
>  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;
> +	INIT_LIST_HEAD(&q->list);
> +	mutex_lock(&matrix_dev->lock);
> +	list_add(&q->list, &matrix_dev->free_list);
> +	mutex_unlock(&matrix_dev->lock);

>From what I can see, dealing with the free_list is supposed to be
protected by the matrix_dev mutex, and at a glance, it indeed seems to
be held every time you interact with the list. I think it would be good
to document that with a comment.

(I have not reviewed this deeply, and I won't be able to look at this
more until April, sorry.)


>  	return 0;
>  }