netdev - [PATCH iwl-next v6 1/6] igb: Always call igb_xdp_ring_update

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Message-Id: <20240711-b4-igb_zero_copy-v6-1-4bfb68773b18@linutronix.de>
Date: Fri, 16 Aug 2024 11:24:00 +0200
From: Kurt Kanzenbach <kurt@...utronix.de>
To: Tony Nguyen <anthony.l.nguyen@...el.com>, 
 Przemek Kitszel <przemyslaw.kitszel@...el.com>
Cc: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 Jesper Dangaard Brouer <hawk@...nel.org>, 
 John Fastabend <john.fastabend@...il.com>, 
 Richard Cochran <richardcochran@...il.com>, 
 Sriram Yagnaraman <sriram.yagnaraman@...csson.com>, 
 Benjamin Steinke <benjamin.steinke@...s-audio.com>, 
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>, 
 Maciej Fijalkowski <maciej.fijalkowski@...el.com>, 
 intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org, 
 bpf@...r.kernel.org, Sriram Yagnaraman <sriram.yagnaraman@....tech>, 
 Kurt Kanzenbach <kurt@...utronix.de>
Subject: [PATCH iwl-next v6 1/6] igb: Always call
 igb_xdp_ring_update_tail() under Tx lock

From: Sriram Yagnaraman <sriram.yagnaraman@....tech>

Always call igb_xdp_ring_update_tail() under __netif_tx_lock(), add a
comment to indicate that. This is needed to share the same TX ring between
XDP, XSK and slow paths.

Signed-off-by: Sriram Yagnaraman <sriram.yagnaraman@....tech>
[Kurt: Split patches]
Signed-off-by: Kurt Kanzenbach <kurt@...utronix.de>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 11be39f435f3..4d5e5691c9bd 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -2914,6 +2914,7 @@ static int igb_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 	}
 }

+/* This function assumes __netif_tx_lock is held by the caller. */
 static void igb_xdp_ring_update_tail(struct igb_ring *ring)
 {
 	/* Force memory writes to complete before letting h/w know there
@@ -3000,11 +3001,11 @@ static int igb_xdp_xmit(struct net_device *dev, int n,
 		nxmit++;
 	}

-	__netif_tx_unlock(nq);
-
 	if (unlikely(flags & XDP_XMIT_FLUSH))
 		igb_xdp_ring_update_tail(tx_ring);

+	__netif_tx_unlock(nq);
+
 	return nxmit;
 }

@@ -8853,12 +8854,14 @@ static void igb_put_rx_buffer(struct igb_ring *rx_ring,

 static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
 {
+	unsigned int total_bytes = 0, total_packets = 0;
 	struct igb_adapter *adapter = q_vector->adapter;
 	struct igb_ring *rx_ring = q_vector->rx.ring;
-	struct sk_buff *skb = rx_ring->skb;
-	unsigned int total_bytes = 0, total_packets = 0;
 	u16 cleaned_count = igb_desc_unused(rx_ring);
+	struct sk_buff *skb = rx_ring->skb;
+	int cpu = smp_processor_id();
 	unsigned int xdp_xmit = 0;
+	struct netdev_queue *nq;
 	struct xdp_buff xdp;
 	u32 frame_sz = 0;
 	int rx_buf_pgcnt;
@@ -8986,7 +8989,10 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
 	if (xdp_xmit & IGB_XDP_TX) {
 		struct igb_ring *tx_ring = igb_xdp_tx_queue_mapping(adapter);

+		nq = txring_txq(tx_ring);
+		__netif_tx_lock(nq, cpu);
 		igb_xdp_ring_update_tail(tx_ring);
+		__netif_tx_unlock(nq);
 	}

 	u64_stats_update_begin(&rx_ring->rx_syncp);

-- 
2.39.2