Re: [PATCH v10 02/16] s390/vfio-ap: use new AP bus interface to search for queue devices

[Tony Krowiak]

On 9/24/20 10:27 PM, Halil Pasic wrote:

On Fri, 21 Aug 2020 15:56:02 -0400
Tony Krowiak <akrow...@linux.ibm.com> wrote:

--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -26,43 +26,26 @@

static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev); -static int match_apqn(struct device *dev, const void *data)

-{
-       struct vfio_ap_queue *q = dev_get_drvdata(dev);
-
-       return (q->apqn == *(int *)(data)) ? 1 : 0;
-}
-
  /**
- * vfio_ap_get_queue: Retrieve a queue with a specific APQN from a list
- * @matrix_mdev: the associated mediated matrix
+ * vfio_ap_get_queue: Retrieve a queue with a specific APQN.
   * @apqn: The queue APQN
   *
- * Retrieve a queue with a specific APQN from the list of the
- * devices of the vfio_ap_drv.
- * Verify that the APID and the APQI are set in the matrix.
+ * Retrieve a queue with a specific APQN from the AP queue devices attached to
+ * the AP bus.
   *
- * Returns the pointer to the associated vfio_ap_queue
+ * Returns the pointer to the vfio_ap_queue with the specified APQN, or NULL.
   */
-static struct vfio_ap_queue *vfio_ap_get_queue(
-                                       struct ap_matrix_mdev *matrix_mdev,
-                                       int apqn)
+static struct vfio_ap_queue *vfio_ap_get_queue(unsigned long apqn)
  {
+       struct ap_queue *queue;
        struct vfio_ap_queue *q;
-       struct device *dev;

- if (!test_bit_inv(AP_QID_CARD(apqn), matrix_mdev->matrix.apm))

-               return NULL;
-       if (!test_bit_inv(AP_QID_QUEUE(apqn), matrix_mdev->matrix.aqm))
+       queue = ap_get_qdev(apqn);
+       if (!queue)
                return NULL;

- dev = driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL,

-                                &apqn, match_apqn);
-       if (!dev)
-               return NULL;
-       q = dev_get_drvdata(dev);
-       q->matrix_mdev = matrix_mdev;
-       put_device(dev);
+       q = dev_get_drvdata(&queue->ap_dev.device);

Is this cast here safe? (I don't think it is.)

In the probe, we execute:
dev_set_drvdata(&queue->ap_dev.device, q);

I don't get any compile nor execution errors. Why wouldn't it be safe?

+       put_device(&queue->ap_dev.device);

return q;

  }