s390/qeth: allow configuration of TX queues for IQD devices

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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>

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Julian Wiedmann 2020-03-18 13:54:49 +01:00 • committed by David S. Miller

parent fcc2df8b87

commit 66cddf1019

2 changed files with 21 additions and 4 deletions

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6

drivers/s390/net/qeth_core_main.c

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19

drivers/s390/net/qeth_ethtool.c

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