linux-kernel - Re: [PATCH v4 3/7] s390: ap: associate a ap_vfio

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Date:   Mon, 4 Mar 2019 03:09:35 +0100
From:   Halil Pasic <pasic@...ux.ibm.com>
To:     Pierre Morel <pmorel@...ux.ibm.com>
Cc:     borntraeger@...ibm.com, alex.williamson@...hat.com,
        cohuck@...hat.com, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        frankja@...ux.ibm.com, akrowiak@...ux.ibm.com, david@...hat.com,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        freude@...ux.ibm.com, mimu@...ux.ibm.com
Subject: Re: [PATCH v4 3/7] s390: ap: associate a ap_vfio_queue and a matrix
 mdev

On Fri, 22 Feb 2019 16:29:56 +0100
Pierre Morel <pmorel@...ux.ibm.com> wrote:

> We need to associate the ap_vfio_queue, which will hold the
> per queue information for interrupt with a matrix mediated device
> which hold the configuration and the way to the CRYCB.
[..]
> +static int vfio_ap_get_all_domains(struct ap_matrix_mdev *matrix_mdev, int apid)
> +{
> +	int apqi, apqn;
> +	int ret = 0;
> +	struct vfio_ap_queue *q;
> +	struct list_head q_list;
> +
> +	INIT_LIST_HEAD(&q_list);
> +
> +	for_each_set_bit_inv(apqi, matrix_mdev->matrix.aqm, AP_DOMAINS) {
> +		apqn = AP_MKQID(apid, apqi);
> +		q = vfio_ap_get_queue(apqn, &matrix_dev->free_list);
> +		if (!q) {
> +			ret = -EADDRNOTAVAIL;
> +			goto rewind;
> +		}
> +		if (q->matrix_mdev) {
> +			ret = -EADDRINUSE;

You tried to get the q from matrix_dev->free_list thus modulo races
q->matrix_mdev should be 0. This change breaks the error codes in a
sense that it becomes impossible to provoke EADDRINUSE (the proper
error code for taken by another matrix_mdev). 

> +			goto rewind;
> +		}
> +		list_move(&q->list, &q_list);
> +	}
> +	move_and_set(&q_list, &matrix_mdev->qlist, matrix_mdev);
>  	return 0;
> +rewind:
> +	move_and_set(&q_list, &matrix_dev->free_list, NULL);
> +	return ret;
>  }
> -
>  /**
> - * vfio_ap_mdev_verify_no_sharing
> + * vfio_ap_get_all_cards:
>   *
> - * Verifies that the APQNs derived from the cross product of the AP adapter IDs
> - * and AP queue indexes comprising the AP matrix are not configured for another
> - * mediated device. AP queue sharing is not allowed.
> + * @matrix_mdev: the matrix mediated device for which we want to associate
> + *		 all available queues with a given apqi.
> + * @apqi:	 The apqi which associated with all defined APID of the
> + *		 mediated device will define a AP queue.
>   *
> - * @matrix_mdev: the mediated matrix device
> + * We define a local list to put all queues we find on the matrix device
> + * free list when associating the apqi with all already defined apid for
> + * this matrix mediated device.
>   *
> - * Returns 0 if the APQNs are not shared, otherwise; returns -EADDRINUSE.
> + * If we can get all the devices we roll them to the mediated device list
> + * If we get errors we unroll them to the free list.
>   */
> -static int vfio_ap_mdev_verify_no_sharing(struct ap_matrix_mdev *matrix_mdev)
> +static int vfio_ap_get_all_cards(struct ap_matrix_mdev *matrix_mdev, int apqi)
>  {
> -	struct ap_matrix_mdev *lstdev;
> -	DECLARE_BITMAP(apm, AP_DEVICES);
> -	DECLARE_BITMAP(aqm, AP_DOMAINS);
> -
> -	list_for_each_entry(lstdev, &matrix_dev->mdev_list, node) {
> -		if (matrix_mdev == lstdev)
> -			continue;
> -
> -		memset(apm, 0, sizeof(apm));
> -		memset(aqm, 0, sizeof(aqm));
> -
> -		/*
> -		 * We work on full longs, as we can only exclude the leftover
> -		 * bits in non-inverse order. The leftover is all zeros.
> -		 */
> -		if (!bitmap_and(apm, matrix_mdev->matrix.apm,
> -				lstdev->matrix.apm, AP_DEVICES))
> -			continue;
> -
> -		if (!bitmap_and(aqm, matrix_mdev->matrix.aqm,
> -				lstdev->matrix.aqm, AP_DOMAINS))
> -			continue;
> -
> -		return -EADDRINUSE;
> +	int apid, apqn;
> +	int ret = 0;
> +	struct vfio_ap_queue *q;
> +	struct list_head q_list;
> +	struct ap_matrix_mdev *tmp = NULL;
> +
> +	INIT_LIST_HEAD(&q_list);
> +
> +	for_each_set_bit_inv(apid, matrix_mdev->matrix.apm, AP_DEVICES) {
> +		apqn = AP_MKQID(apid, apqi);
> +		q = vfio_ap_get_queue(apqn, &matrix_dev->free_list);
> +		if (!q) {
> +			ret = -EADDRNOTAVAIL;
> +			goto rewind;
> +		}
> +		if (q->matrix_mdev) {
> +			ret = -EADDRINUSE;

Same here!

Regards,
Halil

> +			goto rewind;
> +		}
> +		list_move(&q->list, &q_list);
>  	}

[..]