[ovs-git] [openvswitch/ovs] f598f4: dpif-netdev: Force port reconfiguration to change ...

[Ilya Maximets]

  Branch: refs/heads/master
  Home:   https://github.com/openvswitch/ovs
  Commit: f598f46212d698f091408abd6ff6905a16980169
      https://github.com/openvswitch/ovs/commit/f598f46212d698f091408abd6ff6905a16980169
  Author: Ilya Maximets <i.maximets at ovn.org>
  Date:   2020-03-25 (Wed, 25 Mar 2020)

  Changed paths:
    M lib/dpif-netdev.c

  Log Message:
  -----------
  dpif-netdev: Force port reconfiguration to change dynamic_txqs.

In case number of polling threads goes from exact number of Tx queues
in port to higher value while set_tx_multiq() not implemented or not
requesting reconfiguration, port will not be reconfigured and datapath
will continue using static Tx queue ids leading to crash.

Ex.:
 Assuming that port p0 supports up to 4 Tx queues and doesn't support
 set_tx_multiq() method.  For example, netdev-afxdp could be the case,
 because it could have multiple Tx queues, but doesn't have
 set_tx_multiq() implementation because number of Tx queues always
 equals to number of Rx queues.

 1. Configuring pmd-cpu-mask to have 3 pmd threads.

 2. Adding port p0 to OVS.
    At this point wanted_txqs = 4 (3 for pmd threads + 1 for non-pmd).
    Port reconfigured to have 4 Tx queues successfully.
    dynamic_txqs = (4 < 4) = false;

 3. Configuring pmd-cpu-mask to have 10 pmd threads.
    At this point wanted_txqs = 11 (10 for pmd threads + 1 for non-pmd).
    Since set_tx_multiq() is not implemented, netdev doesn't request
    reconfiguration and 'dynamic_txqs' remains in 'false' state.

 4. Since 'dynamic_txqs == false', dpif-netdev uses static Tx queue
    ids that are in range [0, 10] while device only supports 4 leading
    to unwanted behavior and crashes.

Fix that by marking for reconfiguration all the ports that will likely
change their 'dynamic_txqs' value.

It looks like the issue could be reproduced only with afxdp ports,
because all other non-dpdk ports ignores Tx queue ids and dpdk ports
requests for reconfiguration on set_tx_multiq().

Reported-by: William Tu <u9012063 at gmail.com>
Reported-at: https://mail.openvswitch.org/pipermail/ovs-dev/2020-March/368364.html
Fixes: e32971b8ddb4 ("dpif-netdev: Centralized threads and queues handling code.")
Acked-by: Kevin Traynor <ktraynor at redhat.com>
Signed-off-by: Ilya Maximets <i.maximets at ovn.org>
Signed-off-by: William Tu <u9012063 at gmail.com>