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    SubjectRe: [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@linux.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);
    > }

    [..]

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