netdev - [PATCH bpf 3/4] ice: xsk: stop Rx processing when ntc catches ntu

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Message-Id: <20220328142123.170157-4-maciej.fijalkowski@intel.com>
Date:   Mon, 28 Mar 2022 16:21:22 +0200
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net
Cc:     netdev@...r.kernel.org, magnus.karlsson@...el.com,
        alexandr.lobakin@...el.com, bjorn@...nel.org,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Subject: [PATCH bpf 3/4] ice: xsk: stop Rx processing when ntc catches ntu

This can happen with big budget values and some breakage of re-filling
descriptors as we do not clear the entry that ntu is pointing at the end
of ice_alloc_rx_bufs_zc. So if ntc is at ntu then it might be the case
that status_error0 has an old, uncleared value and ntc would go over
with processing which would result in false results.

Break Rx loop when ntc == ntu to avoid broken behavior.

Fixes: 3876ff525de7 ("ice: xsk: Handle SW XDP ring wrap and bump tail more often")
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
---
 drivers/net/ethernet/intel/ice/ice_xsk.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
index 51427cb4971a..dfbcaf08520e 100644
--- a/drivers/net/ethernet/intel/ice/ice_xsk.c
+++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
@@ -608,6 +608,9 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
 		 */
 		dma_rmb();
 
+		if (unlikely(rx_ring->next_to_clean == rx_ring->next_to_use))
+			break;
+
 		xdp = *ice_xdp_buf(rx_ring, rx_ring->next_to_clean);
 
 		size = le16_to_cpu(rx_desc->wb.pkt_len) &
-- 
2.27.0