After rx/tx ring buffer size is changed, kernel panic occurs when
it acts XDP_TX or XDP_REDIRECT.

When tx/rx ring buffer size is changed(ethtool -G), sfc driver
reallocates and reinitializes rx and tx queues and their buffers
(tx_queue->buffer).
But it misses reinitializing xdp queues and buffers.
So, while it is acting XDP_TX or XDP_REDIRECT, it uses the uninitialized
tx_queue->buffer.

A new function efx_set_xdp_channels() is separated from efx_set_channels()
to handle only xdp queues.

Splat looks like:
    BUG: kernel NULL pointer dereference, address: 000000000000002a
    #PF: supervisor write access in kernel mode
    #PF: error_code(0x0002) - not-present page
    PGD 0 P4D 0
    Oops: 0002 [#4] PREEMPT SMP NOPTI
    RIP: 0010:efx_tx_map_chunk+0x54/0x90 [sfc]
    CPU: 2 PID: 0 Comm: swapper/2 Tainted: G      D           5.17.0+ #55 e8beeee8289528f11357029357cf
    Code: 48 8b 8d a8 01 00 00 48 8d 14 52 4c 8d 2c d0 44 89 e0 48 85 c9 74 0e 44 89 e2 4c 89 f6 48 80
    RSP: 0018:ffff92f121e45c60 EFLAGS: 00010297
    RIP: 0010:efx_tx_map_chunk+0x54/0x90 [sfc]
    RAX: 0000000000000040 RBX: ffff92ea506895c0 RCX: ffffffffc0330870
    RDX: 0000000000000001 RSI: 00000001139b10ce RDI: ffff92ea506895c0
    RBP: ffffffffc0358a80 R08: 00000001139b110d R09: 0000000000000000
    R10: 0000000000000001 R11: ffff92ea414c0088 R12: 0000000000000040
    R13: 0000000000000018 R14: 00000001139b10ce R15: ffff92ea506895c0
    FS:  0000000000000000(0000) GS:ffff92f121ec0000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    Code: 48 8b 8d a8 01 00 00 48 8d 14 52 4c 8d 2c d0 44 89 e0 48 85 c9 74 0e 44 89 e2 4c 89 f6 48 80
    CR2: 000000000000002a CR3: 00000003e6810004 CR4: 00000000007706e0
    RSP: 0018:ffff92f121e85c60 EFLAGS: 00010297
    PKRU: 55555554
    RAX: 0000000000000040 RBX: ffff92ea50689700 RCX: ffffffffc0330870
    RDX: 0000000000000001 RSI: 00000001145a90ce RDI: ffff92ea50689700
    RBP: ffffffffc0358a80 R08: 00000001145a910d R09: 0000000000000000
    R10: 0000000000000001 R11: ffff92ea414c0088 R12: 0000000000000040
    R13: 0000000000000018 R14: 00000001145a90ce R15: ffff92ea50689700
    FS:  0000000000000000(0000) GS:ffff92f121e80000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 000000000000002a CR3: 00000003e6810005 CR4: 00000000007706e0
    PKRU: 55555554
    Call Trace:
     <IRQ>
     efx_xdp_tx_buffers+0x12b/0x3d0 [sfc 84c94b8e32d44d296c17e10a634d3ad454de4ba5]
     __efx_rx_packet+0x5c3/0x930 [sfc 84c94b8e32d44d296c17e10a634d3ad454de4ba5]
     efx_rx_packet+0x28c/0x2e0 [sfc 84c94b8e32d44d296c17e10a634d3ad454de4ba5]
     efx_ef10_ev_process+0x5f8/0xf40 [sfc 84c94b8e32d44d296c17e10a634d3ad454de4ba5]
     ? enqueue_task_fair+0x95/0x550
     efx_poll+0xc4/0x360 [sfc 84c94b8e32d44d296c17e10a634d3ad454de4ba5]

Fixes: 3990a8fffbda ("sfc: allocate channels for XDP tx queues")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
---
  drivers/net/ethernet/sfc/efx_channels.c | 147 +++++++++++++-----------
  1 file changed, 82 insertions(+), 65 deletions(-)

diff --git a/drivers/net/ethernet/sfc/efx_channels.c b/drivers/net/ethernet/sfc/efx_channels.c
index d6fdcdc530ca..271f3bdfc141 100644
--- a/drivers/net/ethernet/sfc/efx_channels.c
+++ b/drivers/net/ethernet/sfc/efx_channels.c

@@ -789,6 +789,86 @@ void efx_remove_channels(struct efx_nic *efx)
  	kfree(efx->xdp_tx_queues);
  }
  
+static inline int efx_set_xdp_tx_queue(struct efx_nic *efx,