RDMA/bnxt_re: Add check for path mtu in modify_qp

When RDMA app configures path MTU, add a check in modify_qp verb
to make sure that it doesn't go beyond interface MTU. If this
check fails, driver will fail the modify_qp verb.

Fixes: 1ac5a40 ("RDMA/bnxt_re: Add bnxt_re RoCE driver")
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: Saravanan Vajravel <saravanan.vajravel@broadcom.com>
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Link: https://patch.msgid.link/20241211083931.968831-3-kalesh-anakkur.purayil@broadcom.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/hw/bnxt_re/ib_verbs.c

@@ -2162,18 +2162,20 @@ int bnxt_re_modify_qp(struct ib_qp *ib_qp, struct ib_qp_attr *qp_attr,
 		}
 	}
 
-	if (qp_attr_mask & IB_QP_PATH_MTU) {
-		qp->qplib_qp.modify_flags |=
-				CMDQ_MODIFY_QP_MODIFY_MASK_PATH_MTU;
-		qp->qplib_qp.path_mtu = __from_ib_mtu(qp_attr->path_mtu);
-		qp->qplib_qp.mtu = ib_mtu_enum_to_int(qp_attr->path_mtu);
-	} else if (qp_attr->qp_state == IB_QPS_RTR) {
-		qp->qplib_qp.modify_flags |=
-			CMDQ_MODIFY_QP_MODIFY_MASK_PATH_MTU;
-		qp->qplib_qp.path_mtu =
-			__from_ib_mtu(iboe_get_mtu(rdev->netdev->mtu));
-		qp->qplib_qp.mtu =
-			ib_mtu_enum_to_int(iboe_get_mtu(rdev->netdev->mtu));
+	if (qp_attr->qp_state == IB_QPS_RTR) {
+		enum ib_mtu qpmtu;
+
+		qpmtu = iboe_get_mtu(rdev->netdev->mtu);
+		if (qp_attr_mask & IB_QP_PATH_MTU) {
+			if (ib_mtu_enum_to_int(qp_attr->path_mtu) >
+			    ib_mtu_enum_to_int(qpmtu))
+				return -EINVAL;
+			qpmtu = qp_attr->path_mtu;
+		}
+
+		qp->qplib_qp.modify_flags |= CMDQ_MODIFY_QP_MODIFY_MASK_PATH_MTU;
+		qp->qplib_qp.path_mtu = __from_ib_mtu(qpmtu);
+		qp->qplib_qp.mtu = ib_mtu_enum_to_int(qpmtu);
 	}
 
 	if (qp_attr_mask & IB_QP_TIMEOUT) {