netdev - [PATCH bpf-next 04/10] i40e: xsk: terminate NAPI when XSK Rx queue gets full

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Date:   Tue,  5 Apr 2022 13:06:25 +0200
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        magnus.karlsson@...el.com, bjorn@...nel.org
Cc:     netdev@...r.kernel.org, brouer@...hat.com, maximmi@...dia.com,
        alexandr.lobakin@...el.com,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Subject: [PATCH bpf-next 04/10] i40e: xsk: terminate NAPI when XSK Rx queue gets full

Correlate -ENOBUFS that was returned from xdp_do_redirect() with a XSK
Rx queue being full. In such case, terminate the softirq processing and
let the user space to consume descriptors from XSK Rx queue so that
there is room that driver can use later on.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
---
 .../ethernet/intel/i40e/i40e_txrx_common.h    |  1 +
 drivers/net/ethernet/intel/i40e/i40e_xsk.c    | 21 ++++++++++++-------
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx_common.h b/drivers/net/ethernet/intel/i40e/i40e_txrx_common.h
index 19da3b22160f..8c5118c8baaf 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx_common.h
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx_common.h
@@ -20,6 +20,7 @@ void i40e_release_rx_desc(struct i40e_ring *rx_ring, u32 val);
 #define I40E_XDP_CONSUMED	BIT(0)
 #define I40E_XDP_TX		BIT(1)
 #define I40E_XDP_REDIR		BIT(2)
+#define I40E_XDP_EXIT		BIT(3)
 
 /*
  * build_ctob - Builds the Tx descriptor (cmd, offset and type) qword
diff --git a/drivers/net/ethernet/intel/i40e/i40e_xsk.c b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
index c1d25b0b0ca2..9f9e4ce9a24d 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_xsk.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
@@ -161,9 +161,10 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
 
 	if (likely(act == XDP_REDIRECT)) {
 		err = xdp_do_redirect(rx_ring->netdev, xdp, xdp_prog);
-		if (err)
-			goto out_failure;
-		return I40E_XDP_REDIR;
+		if (!err)
+			return I40E_XDP_REDIR;
+		result = (err == -ENOBUFS) ? I40E_XDP_EXIT : I40E_XDP_CONSUMED;
+		goto out_failure;
 	}
 
 	switch (act) {
@@ -175,6 +176,9 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
 		if (result == I40E_XDP_CONSUMED)
 			goto out_failure;
 		break;
+	case XDP_DROP:
+		result = I40E_XDP_CONSUMED;
+		break;
 	default:
 		bpf_warn_invalid_xdp_action(rx_ring->netdev, xdp_prog, act);
 		fallthrough;
@@ -182,9 +186,6 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
 out_failure:
 		trace_xdp_exception(rx_ring->netdev, xdp_prog, act);
 		fallthrough; /* handle aborts by dropping packet */
-	case XDP_DROP:
-		result = I40E_XDP_CONSUMED;
-		break;
 	}
 	return result;
 }
@@ -370,6 +371,12 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
 		xsk_buff_dma_sync_for_cpu(bi, rx_ring->xsk_pool);
 
 		xdp_res = i40e_run_xdp_zc(rx_ring, bi);
+		if (xdp_res == I40E_XDP_EXIT) {
+			failure = true;
+			xsk_buff_free(bi);
+			next_to_clean = (next_to_clean + 1) & count_mask;
+			break;
+		}
 		i40e_handle_xdp_result_zc(rx_ring, bi, rx_desc, &rx_packets,
 					  &rx_bytes, size, xdp_res);
 		total_rx_packets += rx_packets;
@@ -382,7 +389,7 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
 	cleaned_count = (next_to_clean - rx_ring->next_to_use - 1) & count_mask;
 
 	if (cleaned_count >= I40E_RX_BUFFER_WRITE)
-		failure = !i40e_alloc_rx_buffers_zc(rx_ring, cleaned_count);
+		failure |= !i40e_alloc_rx_buffers_zc(rx_ring, cleaned_count);
 
 	i40e_finalize_xdp_rx(rx_ring, xdp_xmit);
 	i40e_update_rx_stats(rx_ring, total_rx_bytes, total_rx_packets);
-- 
2.33.1