qos_max_rate and other options are in BITS per second and ovn-controller
is using 32 bit integer to store it:

  uint32_t max_rate = smap_get_int(&pb->options, "qos_max_rate", 0);

That limits the maximum value to just 4 Gbps, while 34 Gbps should
be technically possible with netdev_set_qos() API.

64bit values should be used instead.  Also limits are not documented
anywhere, while they should be.

Why 34 Gbps is a max described in BZ 2137619.