From: =?UTF-8?q?=C3=8D=C3=B1igo=20Huguet?= <ihuguet@redhat.com>

Date: Wed, 14 Sep 2022 12:36:48 +0200

Subject: sfc: fix TX channel offset when using legacy interrupts

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Patch-mainline: v6.0-rc7

Git-commit: f232af4295653afa4ade3230462b3be15ad16419

References: git-fixes

In legacy interrupt mode the tx_channel_offset was hardcoded to 1, but

that's not correct if efx_sepparate_tx_channels is false. In that case,

the offset is 0 because the tx queues are in the single existing channel

at index 0, together with the rx queue.

Without this fix, as soon as you try to send any traffic, it tries to

get the tx queues from an uninitialized channel getting these errors:

  WARNING: CPU: 1 PID: 0 at drivers/net/ethernet/sfc/tx.c:540 efx_hard_start_xmit+0x12e/0x170 [sfc]

  [...]

  RIP: 0010:efx_hard_start_xmit+0x12e/0x170 [sfc]

  [...]

  Call Trace:

   <IRQ>

   dev_hard_start_xmit+0xd7/0x230

   sch_direct_xmit+0x9f/0x360

   __dev_queue_xmit+0x890/0xa40

  [...]

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000020

  [...]

  RIP: 0010:efx_hard_start_xmit+0x153/0x170 [sfc]

  [...]

  Call Trace:

   <IRQ>

   dev_hard_start_xmit+0xd7/0x230

   sch_direct_xmit+0x9f/0x360

   __dev_queue_xmit+0x890/0xa40

  [...]

Fixes: c308dfd1b43e ("sfc: fix wrong tx channel offset with efx_separate_tx_channels")

Reported-by: Tianhao Zhao <tizhao@redhat.com>

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

Acked-by: Edward Cree <ecree.xilinx@gmail.com>

Link: https://lore.kernel.org/r/20220914103648.16902-1-ihuguet@redhat.com

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>

---

 drivers/net/ethernet/sfc/efx_channels.c |    2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/ethernet/sfc/efx_channels.c

+++ b/drivers/net/ethernet/sfc/efx_channels.c

@@ -329,7 +329,7 @@ int efx_probe_interrupts(struct efx_nic

 		efx->n_channels = 1 + (efx_separate_tx_channels ? 1 : 0);

 		efx->n_rx_channels = 1;

 		efx->n_tx_channels = 1;

-		efx->tx_channel_offset = 1;

+		efx->tx_channel_offset = efx_separate_tx_channels ? 1 : 0;

 		efx->n_xdp_channels = 0;

 		efx->xdp_channel_offset = efx->n_channels;

 		efx->legacy_irq = efx->pci_dev->irq;