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net: lan966x: don't free XDP buffers in fdma tx clear with budget 0

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lan966x_fdma_tx_clear_buf() runs from the NAPI poll and frees the
buffers of completed tx DCBs with napi_consume_skb(),
page_pool_recycle_direct() and xdp_return_frame_bulk().

netpoll calls the NAPI poll with a budget of 0 and hardirqs disabled.
With a budget of 0, a driver cannot call any XDP or page pool API.

Before this patch, the XDP_TX pages and ndo_xdp_xmit frames are freed
regardless of the budget. With netconsole on the port that owns the
FDMA NAPI, such a buffer is freed with hardirqs disabled, and
__page_pool_put_page() warns via lockdep_assert_no_hardirq().

Leave the XDP buffers of completed DCBs in place when the budget is 0,
and free them in the next NAPI poll. napi_consume_skb() already handles
a budget of 0, so skbs are still freed.

Found by an AI code review agent. Reproduced on a lan9668 board with a
modified kernel that runs the NAPI poll with a budget of 0 and hardirqs
disabled. With the fix the warning is gone.

Fixes: 19c6f534f6 ("net: lan966x: Add support for XDP_TX")
Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20261029-lan966x-fdma-tx-clear-budget-v1-1-38c52d7aab8c@microchip.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Daniel Machon 2026-10-29 12:47:47 +01:00 committed by Paolo Abeni
parent 21f57ec673
commit 263a5514cb
1 changed files with 6 additions and 0 deletions
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6
drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
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@ -353,6 +353,12 @@ static void lan966x_fdma_tx_clear_buf(struct lan966x *lan966x, int weight)
if (!fdma_db_is_done(db))
continue;
/* XDP and page pool APIs can't be used with a budget of 0.
* Leave these buffers for the next NAPI poll.
*/
if (!weight && !dcb_buf->use_skb)
continue;
dcb_buf->dev->stats.tx_packets++;
dcb_buf->dev->stats.tx_bytes += dcb_buf->len;