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

On Fri, 21 Aug 2020 15:56:02 -0400
Tony Krowiak [off-list ref] wrote:

quoted

--- 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?

quoted

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