From: Taehee Yoo <ap420073@gmail.com>
Date: Tue, 5 Apr 2022 08:45:44 +0000
Subject: net: sfc: fix using uninitialized xdp tx_queue
Patch-mainline: v5.18-rc2
Git-commit: fb5833d81e4333294add35d3ac7f7f52a7bf107f
References: git-fixes

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: f28100cb9c96 ("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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/sfc/efx_channels.c |    2 +-
 drivers/net/ethernet/sfc/tx.c           |    3 +++
 drivers/net/ethernet/sfc/tx_common.c    |    2 ++
 3 files changed, 6 insertions(+), 1 deletion(-)

--- a/drivers/net/ethernet/sfc/efx_channels.c
+++ b/drivers/net/ethernet/sfc/efx_channels.c
@@ -1117,7 +1117,7 @@ void efx_start_channels(struct efx_nic *
 	struct efx_rx_queue *rx_queue;
 	struct efx_channel *channel;
 
-	efx_for_each_channel(channel, efx) {
+	efx_for_each_channel_rev(channel, efx) {
 		efx_for_each_channel_tx_queue(tx_queue, channel) {
 			efx_init_tx_queue(tx_queue);
 			atomic_inc(&efx->active_queues);
--- a/drivers/net/ethernet/sfc/tx.c
+++ b/drivers/net/ethernet/sfc/tx.c
@@ -443,6 +443,9 @@ int efx_xdp_tx_buffers(struct efx_nic *e
 	if (unlikely(!tx_queue))
 		return -EINVAL;
 
+	if (!tx_queue->initialised)
+		return -EINVAL;
+
 	if (efx->xdp_txq_queues_mode != EFX_XDP_TX_QUEUES_DEDICATED)
 		HARD_TX_LOCK(efx->net_dev, tx_queue->core_txq, cpu);
 
--- a/drivers/net/ethernet/sfc/tx_common.c
+++ b/drivers/net/ethernet/sfc/tx_common.c
@@ -101,6 +101,8 @@ void efx_fini_tx_queue(struct efx_tx_que
 	netif_dbg(tx_queue->efx, drv, tx_queue->efx->net_dev,
 		  "shutting down TX queue %d\n", tx_queue->queue);
 
+	tx_queue->initialised = false;
+
 	if (!tx_queue->buffer)
 		return;