[PATCH iwl-next v4 4/4] igb: add AF_XDP zero-copy Tx support

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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@xxxxxxxx>
---
 drivers/net/ethernet/intel/igb/igb.h      |  2 +
 drivers/net/ethernet/intel/igb/igb_main.c | 56 +++++++++++++++++++----
 drivers/net/ethernet/intel/igb/igb_xsk.c  | 52 +++++++++++++++++++++
 3 files changed, 101 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
index 39202c40116a..f52a988fe2f0 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,
@@ -836,6 +837,7 @@ int igb_xsk_pool_setup(struct igb_adapter *adapter,
 bool igb_alloc_rx_buffers_zc(struct igb_ring *rx_ring, u16 count);
 void igb_clean_rx_ring_zc(struct igb_ring *rx_ring);
 int igb_clean_rx_irq_zc(struct igb_q_vector *q_vector, const int budget);
+bool igb_xmit_zc(struct igb_ring *tx_ring);
 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 b13cc94ac178..117c3d883529 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -3021,6 +3021,9 @@ static int igb_xdp_xmit(struct net_device *dev, int n,
 	if (unlikely(!tx_ring))
 		return -ENXIO;
 
+	if (unlikely(test_bit(IGB_RING_FLAG_TX_DISABLED, &tx_ring->flags)))
+		return -ENXIO;
+
 	nq = txring_txq(tx_ring);
 	__netif_tx_lock(nq, cpu);
 
@@ -4934,15 +4937,20 @@ 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,
@@ -4973,6 +4981,7 @@ 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 */
@@ -4987,6 +4996,9 @@ 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;
@@ -6520,6 +6532,9 @@ netdev_tx_t igb_xmit_frame_ring(struct sk_buff *skb,
 		return NETDEV_TX_BUSY;
 	}
 
+	if (unlikely(test_bit(IGB_RING_FLAG_TX_DISABLED, &tx_ring->flags)))
+		return NETDEV_TX_BUSY;
+
 	/* record the location of the first descriptor for this packet */
 	first = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
 	first->type = IGB_TYPE_SKB;
@@ -8293,13 +8308,17 @@ 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;
-	struct igb_ring *tx_ring = q_vector->tx.ring;
-	struct igb_tx_buffer *tx_buffer;
-	union e1000_adv_tx_desc *tx_desc;
 	unsigned int total_bytes = 0, total_packets = 0;
+	struct igb_adapter *adapter = q_vector->adapter;
 	unsigned int budget = q_vector->tx.work_limit;
+	struct igb_ring *tx_ring = q_vector->tx.ring;
 	unsigned int i = tx_ring->next_to_clean;
+	union e1000_adv_tx_desc *tx_desc;
+	struct igb_tx_buffer *tx_buffer;
+	int cpu = smp_processor_id();
+	bool xsk_xmit_done = true;
+	struct netdev_queue *nq;
+	u32 xsk_frames = 0;
 
 	if (test_bit(__IGB_DOWN, &adapter->state))
 		return true;
@@ -8330,10 +8349,14 @@ 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,
@@ -8365,6 +8388,7 @@ 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++;
@@ -8393,6 +8417,20 @@ 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);
+		__netif_tx_unlock(nq);
+	}
+
 	if (test_bit(IGB_RING_FLAG_TX_DETECT_HANG, &tx_ring->flags)) {
 		struct e1000_hw *hw = &adapter->hw;
 
@@ -8455,7 +8493,7 @@ 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 5e0244772914..c5d01d65e7de 100644
--- a/drivers/net/ethernet/intel/igb/igb_xsk.c
+++ b/drivers/net/ethernet/intel/igb/igb_xsk.c
@@ -432,6 +432,58 @@ 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 = igb_desc_unused(tx_ring);
+	struct xsk_buff_pool *pool = tx_ring->xsk_pool;
+	struct xdp_desc *descs = pool->tx_descs;
+	union e1000_adv_tx_desc *tx_desc = NULL;
+	struct igb_tx_buffer *tx_buffer_info;
+	u32 cmd_type, nb_pkts, i = 0;
+	unsigned int total_bytes = 0;
+	dma_addr_t dma;
+
+	nb_pkts = xsk_tx_peek_release_desc_batch(pool, budget);
+	if (!nb_pkts)
+		return true;
+
+	while (nb_pkts-- > 0) {
+		dma = xsk_buff_raw_get_dma(pool, descs[i].addr);
+		xsk_buff_raw_dma_sync_for_device(pool, dma, descs[i].len);
+
+		tx_buffer_info = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
+		tx_buffer_info->bytecount = descs[i].len;
+		tx_buffer_info->type = IGB_TYPE_XSK;
+		tx_buffer_info->xdpf = NULL;
+		tx_buffer_info->gso_segs = 1;
+		tx_buffer_info->time_stamp = jiffies;
+
+		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 |= descs[i].len | IGB_TXD_DCMD;
+		tx_desc->read.cmd_type_len = cpu_to_le32(cmd_type);
+		tx_desc->read.olinfo_status = 0;
+
+		total_bytes += descs[i].len;
+
+		i++;
+		tx_ring->next_to_use++;
+		tx_buffer_info->next_to_watch = tx_desc;
+		if (tx_ring->next_to_use == tx_ring->count)
+			tx_ring->next_to_use = 0;
+	}
+
+	netdev_tx_sent_queue(txring_txq(tx_ring), total_bytes);
+	igb_xdp_ring_update_tail(tx_ring);
+
+	return nb_pkts < budget;
+}
+
 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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