Date: Tue,  4 Jul 2023 11:59:15 +0200
From: Sriram Yagnaraman <sriram.yagnaraman@....tech>
To:
Cc: intel-wired-lan@...ts.osuosl.org, bpf@...r.kernel.org,
        netdev@...r.kernel.org, Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        "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>,
        Sriram Yagnaraman <sriram.yagnaraman@....tech>
Subject: [PATCH 4/4] igb: add AF_XDP zero-copy Tx support

Add support for AF_XDP zero-copy transmit path.

A new TX buffer type IGB_TYPE_XSK is introduced to indicate that the Tx
frame was allocated from the xsk buff pool, so igb_clean_tx_ring and
igb_clean_tx_irq can clean the buffers correctly based on type.

igb_xmit_zc performs the actual packet transmit when AF_XDP zero-copy is
enabled. We share the TX ring between slow path, XDP and AF_XDP
zero-copy, so we use the netdev queue lock to ensure mutual exclusion.

Signed-off-by: Sriram Yagnaraman <sriram.yagnaraman@....tech>
---
 drivers/net/ethernet/intel/igb/igb.h      |  2 +
 drivers/net/ethernet/intel/igb/igb_main.c | 44 +++++++++++++--
 drivers/net/ethernet/intel/igb/igb_xsk.c  | 67 ++++++++++++++++++++++-
 3 files changed, 105 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
index 4f474d7338b5..564706ab0646 100644
--- a/drivers/net/ethernet/intel/igb/igb.h
+++ b/drivers/net/ethernet/intel/igb/igb.h
@@ -257,6 +257,7 @@ enum igb_tx_flags {
 enum igb_tx_buf_type {
 	IGB_TYPE_SKB = 0,
 	IGB_TYPE_XDP,
+	IGB_TYPE_XSK
 };
 
 /* wrapper around a pointer to a socket buffer,
@@ -843,6 +844,7 @@ int igb_xsk_pool_setup(struct igb_adapter *adapter,
 		       u16 qid);
 bool igb_alloc_rx_buffers_zc(struct igb_ring *rx_ring, u16 count);
 int igb_clean_rx_irq_zc(struct igb_q_vector *q_vector, const int budget);
+bool igb_xmit_zc(struct igb_ring *tx_ring, unsigned int budget);
 int igb_xsk_wakeup(struct net_device *dev, u32 qid, u32 flags);
 
 #endif /* _IGB_H_ */
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index f4dbb75d6eac..c6bb5b1944c8 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -4390,6 +4390,8 @@ void igb_configure_tx_ring(struct igb_adapter *adapter,
 	u64 tdba = ring->dma;
 	int reg_idx = ring->reg_idx;
 
+	ring->xsk_pool = igb_xsk_pool(adapter, ring);
+
 	wr32(E1000_TDLEN(reg_idx),
 	     ring->count * sizeof(union e1000_adv_tx_desc));
 	wr32(E1000_TDBAL(reg_idx),
@@ -4970,15 +4972,20 @@ static void igb_clean_tx_ring(struct igb_ring *tx_ring)
 {
 	u16 i = tx_ring->next_to_clean;
 	struct igb_tx_buffer *tx_buffer = &tx_ring->tx_buffer_info[i];
+	u32 xsk_frames = 0;
 
 	while (i != tx_ring->next_to_use) {
 		union e1000_adv_tx_desc *eop_desc, *tx_desc;
 
 		/* Free all the Tx ring sk_buffs or xdp frames */
-		if (tx_buffer->type == IGB_TYPE_SKB)
+		if (tx_buffer->type == IGB_TYPE_SKB) {
 			dev_kfree_skb_any(tx_buffer->skb);
-		else
+		} else if (tx_buffer->type == IGB_TYPE_XDP) {
 			xdp_return_frame(tx_buffer->xdpf);
+		} else if (tx_buffer->type == IGB_TYPE_XSK) {
+			xsk_frames++;
+			goto skip_for_xsk;
+		}
 
 		/* unmap skb header data */
 		dma_unmap_single(tx_ring->dev,
@@ -5009,6 +5016,7 @@ static void igb_clean_tx_ring(struct igb_ring *tx_ring)
 					       DMA_TO_DEVICE);
 		}
 
+skip_for_xsk:
 		tx_buffer->next_to_watch = NULL;
 
 		/* move us one more past the eop_desc for start of next pkt */
@@ -5023,6 +5031,9 @@ static void igb_clean_tx_ring(struct igb_ring *tx_ring)
 	/* reset BQL for queue */
 	netdev_tx_reset_queue(txring_txq(tx_ring));
 
+	if (tx_ring->xsk_pool && xsk_frames)
+		xsk_tx_completed(tx_ring->xsk_pool, xsk_frames);
+
 	/* reset next_to_use and next_to_clean */
 	tx_ring->next_to_use = 0;
 	tx_ring->next_to_clean = 0;
@@ -8330,12 +8341,16 @@ static int igb_poll(struct napi_struct *napi, int budget)
 static bool igb_clean_tx_irq(struct igb_q_vector *q_vector, int napi_budget)
 {
 	struct igb_adapter *adapter = q_vector->adapter;
+	int cpu = smp_processor_id();
 	struct igb_ring *tx_ring = q_vector->tx.ring;
 	struct igb_tx_buffer *tx_buffer;
 	union e1000_adv_tx_desc *tx_desc;
+	struct netdev_queue *nq;
 	unsigned int total_bytes = 0, total_packets = 0;
 	unsigned int budget = q_vector->tx.work_limit;
 	unsigned int i = tx_ring->next_to_clean;
+	u32 xsk_frames = 0;
+	bool xsk_xmit_done = true;
 
 	if (test_bit(__IGB_DOWN, &adapter->state))
 		return true;
@@ -8366,10 +8381,14 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector, int napi_budget)
 		total_packets += tx_buffer->gso_segs;
 
 		/* free the skb */
-		if (tx_buffer->type == IGB_TYPE_SKB)
+		if (tx_buffer->type == IGB_TYPE_SKB) {
 			napi_consume_skb(tx_buffer->skb, napi_budget);
-		else
+		} else if (tx_buffer->type == IGB_TYPE_XDP) {
 			xdp_return_frame(tx_buffer->xdpf);
+		} else if (tx_buffer->type == IGB_TYPE_XSK) {
+			xsk_frames++;
+			goto skip_for_xsk;
+		}
 
 		/* unmap skb header data */
 		dma_unmap_single(tx_ring->dev,
@@ -8401,6 +8420,7 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector, int napi_budget)
 			}
 		}
 
+skip_for_xsk:
 		/* move us one more past the eop_desc for start of next pkt */
 		tx_buffer++;
 		tx_desc++;
@@ -8429,6 +8449,20 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector, int napi_budget)
 	q_vector->tx.total_bytes += total_bytes;
 	q_vector->tx.total_packets += total_packets;
 
+	if (tx_ring->xsk_pool) {
+		if (xsk_frames)
+			xsk_tx_completed(tx_ring->xsk_pool, xsk_frames);
+		if (xsk_uses_need_wakeup(tx_ring->xsk_pool))
+			xsk_set_tx_need_wakeup(tx_ring->xsk_pool);
+
+		nq = txring_txq(tx_ring);
+		__netif_tx_lock(nq, cpu);
+		/* Avoid transmit queue timeout since we share it with the slow path */
+		txq_trans_cond_update(nq);
+		xsk_xmit_done = igb_xmit_zc(tx_ring, q_vector->tx.work_limit);
+		__netif_tx_unlock(nq);
+	}
+
 	if (test_bit(IGB_RING_FLAG_TX_DETECT_HANG, &tx_ring->flags)) {
 		struct e1000_hw *hw = &adapter->hw;
 
@@ -8491,7 +8525,7 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector, int napi_budget)
 		}
 	}
 
-	return !!budget;
+	return !!budget && xsk_xmit_done;
 }
 
 /**
diff --git a/drivers/net/ethernet/intel/igb/igb_xsk.c b/drivers/net/ethernet/intel/igb/igb_xsk.c
index eae616e7608c..8b60285ec242 100644
--- a/drivers/net/ethernet/intel/igb/igb_xsk.c
+++ b/drivers/net/ethernet/intel/igb/igb_xsk.c
@@ -25,25 +25,28 @@ static int igb_xsk_pool_enable(struct igb_adapter *adapter,
 			       u16 qid)
 {
 	struct net_device *netdev = adapter->netdev;
-	struct igb_ring *rx_ring;
+	struct igb_ring *tx_ring, *rx_ring;
 	bool if_running;
 	int err;
 
 	if (qid >= adapter->num_rx_queues)
 		return -EINVAL;
 
-	if (qid >= netdev->real_num_rx_queues)
+	if (qid >= netdev->real_num_rx_queues ||
+	    qid >= netdev->real_num_tx_queues)
 		return -EINVAL;
 
 	err = xsk_pool_dma_map(pool, &adapter->pdev->dev, IGB_RX_DMA_ATTR);
 	if (err)
 		return err;
 
+	tx_ring = adapter->tx_ring[qid];
 	rx_ring = adapter->rx_ring[qid];
 	if_running = netif_running(adapter->netdev) && igb_xdp_is_enabled(adapter);
 	if (if_running)
 		igb_txrx_ring_disable(adapter, qid);
 
+	set_bit(IGB_RING_FLAG_AF_XDP_ZC, &tx_ring->flags);
 	set_bit(IGB_RING_FLAG_AF_XDP_ZC, &rx_ring->flags);
 
 	if (if_running) {
@@ -52,6 +55,7 @@ static int igb_xsk_pool_enable(struct igb_adapter *adapter,
 		/* Kick start the NAPI context so that receiving will start */
 		err = igb_xsk_wakeup(adapter->netdev, qid, XDP_WAKEUP_RX);
 		if (err) {
+			clear_bit(IGB_RING_FLAG_AF_XDP_ZC, &tx_ring->flags);
 			clear_bit(IGB_RING_FLAG_AF_XDP_ZC, &rx_ring->flags);
 			xsk_pool_dma_unmap(pool, IGB_RX_DMA_ATTR);
 			return err;
@@ -63,7 +67,7 @@ static int igb_xsk_pool_enable(struct igb_adapter *adapter,
 
 static int igb_xsk_pool_disable(struct igb_adapter *adapter, u16 qid)
 {
-	struct igb_ring *rx_ring;
+	struct igb_ring *tx_ring, *rx_ring;
 	struct xsk_buff_pool *pool;
 	bool if_running;
 
@@ -71,12 +75,14 @@ static int igb_xsk_pool_disable(struct igb_adapter *adapter, u16 qid)
 	if (!pool)
 		return -EINVAL;
 
+	tx_ring = adapter->tx_ring[qid];
 	rx_ring = adapter->rx_ring[qid];
 	if_running = netif_running(adapter->netdev) && igb_xdp_is_enabled(adapter);
 	if (if_running)
 		igb_txrx_ring_disable(adapter, qid);
 
 	xsk_pool_dma_unmap(pool, IGB_RX_DMA_ATTR);
+	clear_bit(IGB_RING_FLAG_AF_XDP_ZC, &tx_ring->flags);
 	clear_bit(IGB_RING_FLAG_AF_XDP_ZC, &rx_ring->flags);
 
 	if (if_running)
@@ -335,6 +341,61 @@ int igb_clean_rx_irq_zc(struct igb_q_vector *q_vector, const int budget)
 	return failure ? budget : (int)total_packets;
 }
 
+bool igb_xmit_zc(struct igb_ring *tx_ring, unsigned int budget)
+{
+	struct xsk_buff_pool *pool = tx_ring->xsk_pool;
+	union e1000_adv_tx_desc *tx_desc = NULL;
+	struct igb_tx_buffer *tx_bi;
+	bool work_done = true;
+	struct xdp_desc desc;
+	dma_addr_t dma;
+	u32 cmd_type;
+
+	while (budget-- > 0) {
+		if (unlikely(!igb_desc_unused(tx_ring))) {
+			work_done = false;
+			break;
+		}
+
+		if (!netif_carrier_ok(tx_ring->netdev))
+			break;
+
+		if (!xsk_tx_peek_desc(pool, &desc))
+			break;
+
+		dma = xsk_buff_raw_get_dma(pool, desc.addr);
+		xsk_buff_raw_dma_sync_for_device(pool, dma, desc.len);
+
+		tx_bi = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
+		tx_bi->bytecount = desc.len;
+		tx_bi->type = IGB_TYPE_XSK;
+		tx_bi->xdpf = NULL;
+		tx_bi->gso_segs = 1;
+
+		tx_desc = IGB_TX_DESC(tx_ring, tx_ring->next_to_use);
+		tx_desc->read.buffer_addr = cpu_to_le64(dma);
+
+		/* put descriptor type bits */
+		cmd_type = E1000_ADVTXD_DTYP_DATA | E1000_ADVTXD_DCMD_DEXT |
+			   E1000_ADVTXD_DCMD_IFCS;
+
+		cmd_type |= desc.len | IGB_TXD_DCMD;
+		tx_desc->read.cmd_type_len = cpu_to_le32(cmd_type);
+		tx_desc->read.olinfo_status = 0;
+
+		tx_ring->next_to_use++;
+		if (tx_ring->next_to_use == tx_ring->count)
+			tx_ring->next_to_use = 0;
+	}
+
+	if (tx_desc) {
+		igb_xdp_ring_update_tail(tx_ring);
+		xsk_tx_release(pool);
+	}
+
+	return !!budget && work_done;
+}
+
 int igb_xsk_wakeup(struct net_device *dev, u32 qid, u32 flags)
 {
 	struct igb_adapter *adapter = netdev_priv(dev);
-- 
2.34.1

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