Bugzilla: https://bugzilla.redhat.com/2042841



commit fb5833d81e4333294add35d3ac7f7f52a7bf107f
Author: Taehee Yoo <ap420073@gmail.com>
Date:   Tue Apr 5 08:45:44 2022 +0000

    net: sfc: fix using uninitialized xdp tx_queue
    
    In some cases, xdp tx_queue can get used before initialization.
    1. interface up/down
    2. ring buffer size change
    
    When CPU cores are lower than maximum number of channels of sfc driver,
    it creates new channels only for XDP.
    
    When an interface is up or ring buffer size is changed, all channels
    are initialized.
    But xdp channels are always initialized later.
    So, the below scenario is possible.
    Packets are received to rx queue of normal channels and it is acted
    XDP_TX and tx_queue of xdp channels get used.
    But these tx_queues are not initialized yet.
    If so, TX DMA or queue error occurs.
    
    In order to avoid this problem.
    1. initializes xdp tx_queues earlier than other rx_queue in
    efx_start_channels().
    2. checks whether tx_queue is initialized or not in efx_xdp_tx_buffers().
    
    Splat looks like:
       sfc 0000:08:00.1 enp8s0f1np1: TX queue 10 spurious TX completion id 250
       sfc 0000:08:00.1 enp8s0f1np1: resetting (RECOVER_OR_ALL)
       sfc 0000:08:00.1 enp8s0f1np1: MC command 0x80 inlen 100 failed rc=-22
       (raw=22) arg=789
       sfc 0000:08:00.1 enp8s0f1np1: has been disabled
    
    Fixes: f28100cb ("sfc: fix lack of XDP TX queues - error XDP TX failed (-22)")
Acked-by: Martin Habets <habetsm.xilinx@gmail.com>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Íñigo Huguet <ihuguet@redhat.com>