s390/vfio-ap: Ignore duplicate link requests in vfio_ap_mdev_link_queue

vfio_ap_mdev_link_queue is changed to detect if a matrix_mdev has
already linked the given queue. If so, it bails out.

Signed-off-by: "Jason J. Herne" <jjherne@linux.ibm.com>
Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
Link: https://lore.kernel.org/r/20240415152555.13152-4-jjherne@linux.ibm.com
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

Author: Jason J. Herne

drivers/s390/crypto/vfio_ap_ops.c

@@ -794,10 +794,11 @@ static int vfio_ap_mdev_probe(struct mdev_device *mdev)
 static void vfio_ap_mdev_link_queue(struct ap_matrix_mdev *matrix_mdev,
 				    struct vfio_ap_queue *q)
 {
-	if (q) {
-		q->matrix_mdev = matrix_mdev;
-		hash_add(matrix_mdev->qtable.queues, &q->mdev_qnode, q->apqn);
-	}
+	if (!q || vfio_ap_mdev_get_queue(matrix_mdev, q->apqn))
+		return;
+
+	q->matrix_mdev = matrix_mdev;
+	hash_add(matrix_mdev->qtable.queues, &q->mdev_qnode, q->apqn);
 }
 
 static void vfio_ap_mdev_link_apqn(struct ap_matrix_mdev *matrix_mdev, int apqn)