66cddf1019
Similar to the support for z/VM NICs, but we need to take extra care about the dedicated mcast queue: 1. netdev_pick_tx() is unaware of this limitation and might select the mcast txq. Catch this. 2. require at least _two_ TX queues - one for ucast, one for mcast. 3. when reducing the number of TX queues, there's a potential race where netdev_cap_txqueue() over-rules the selected txq index and falls back to index 0. This would place ucast traffic on the mcast queue, and result in TX errors. So for IQD, reject a reduction while the interface is running. Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com> Signed-off-by: David S. Miller <davem@davemloft.net>