netdev - [RFC net-next 2/2] i40e: add xdp frags support to ndo_xdp

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Date:   Fri, 25 Mar 2022 15:28:12 +0100
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        jesse.brandeburg@...el.com, anthony.l.nguyen@...el.com,
        jbrouer@...hat.com, magnus.karlsson@...el.com, toke@...hat.com,
        lorenzo.bianconi@...hat.com
Subject: [RFC net-next 2/2] i40e: add xdp frags support to ndo_xdp_xmit

Add the capability to map non-linear xdp frames in XDP_TX and ndo_xdp_xmit
callback.

Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
---
 drivers/net/ethernet/intel/i40e/i40e_txrx.c | 86 +++++++++++++++------
 1 file changed, 61 insertions(+), 25 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index 0eae5858f2fe..e9a772db869c 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -3688,35 +3688,55 @@ u16 i40e_lan_select_queue(struct net_device *netdev,
 static int i40e_xmit_xdp_ring(struct xdp_frame *xdpf,
 			      struct i40e_ring *xdp_ring)
 {
-	u16 i = xdp_ring->next_to_use;
-	struct i40e_tx_buffer *tx_bi;
-	struct i40e_tx_desc *tx_desc;
+	struct skb_shared_info *sinfo = xdp_get_shared_info_from_frame(xdpf);
+	u8 nr_frags = unlikely(xdp_frame_has_frags(xdpf)) ? sinfo->nr_frags : 0;
+	u16 i = 0, index = xdp_ring->next_to_use;
+	struct i40e_tx_buffer *tx_head = &xdp_ring->tx_bi[index];
+	struct i40e_tx_buffer *tx_bi = tx_head;
+	struct i40e_tx_desc *tx_desc = I40E_TX_DESC(xdp_ring, index);
 	void *data = xdpf->data;
 	u32 size = xdpf->len;
-	dma_addr_t dma;
 
-	if (!unlikely(I40E_DESC_UNUSED(xdp_ring))) {
+	if (unlikely(I40E_DESC_UNUSED(xdp_ring) < 1 + nr_frags)) {
 		xdp_ring->tx_stats.tx_busy++;
 		return I40E_XDP_CONSUMED;
 	}
-	dma = dma_map_single(xdp_ring->dev, data, size, DMA_TO_DEVICE);
-	if (dma_mapping_error(xdp_ring->dev, dma))
-		return I40E_XDP_CONSUMED;
 
-	tx_bi = &xdp_ring->tx_bi[i];
-	tx_bi->bytecount = size;
-	tx_bi->gso_segs = 1;
-	tx_bi->xdpf = xdpf;
+	tx_head->bytecount = xdp_get_frame_len(xdpf);
+	tx_head->gso_segs = 1;
+	tx_head->xdpf = xdpf;
 
-	/* record length, and DMA address */
-	dma_unmap_len_set(tx_bi, len, size);
-	dma_unmap_addr_set(tx_bi, dma, dma);
+	for (;;) {
+		dma_addr_t dma;
 
-	tx_desc = I40E_TX_DESC(xdp_ring, i);
-	tx_desc->buffer_addr = cpu_to_le64(dma);
-	tx_desc->cmd_type_offset_bsz = build_ctob(I40E_TX_DESC_CMD_ICRC
-						  | I40E_TXD_CMD,
-						  0, size, 0);
+		dma = dma_map_single(xdp_ring->dev, data, size, DMA_TO_DEVICE);
+		if (dma_mapping_error(xdp_ring->dev, dma))
+			goto unmap;
+
+		/* record length, and DMA address */
+		dma_unmap_len_set(tx_bi, len, size);
+		dma_unmap_addr_set(tx_bi, dma, dma);
+
+		tx_desc->buffer_addr = cpu_to_le64(dma);
+		tx_desc->cmd_type_offset_bsz =
+			build_ctob(I40E_TX_DESC_CMD_ICRC, 0, size, 0);
+
+		if (++index == xdp_ring->count)
+			index = 0;
+
+		if (i == nr_frags)
+			break;
+
+		tx_bi = &xdp_ring->tx_bi[index];
+		tx_desc = I40E_TX_DESC(xdp_ring, index);
+
+		data = skb_frag_address(&sinfo->frags[i]);
+		size = skb_frag_size(&sinfo->frags[i]);
+		i++;
+	}
+
+	tx_desc->cmd_type_offset_bsz |=
+		cpu_to_le64(I40E_TXD_CMD << I40E_TXD_QW1_CMD_SHIFT);
 
 	/* Make certain all of the status bits have been updated
 	 * before next_to_watch is written.
@@ -3724,14 +3744,30 @@ static int i40e_xmit_xdp_ring(struct xdp_frame *xdpf,
 	smp_wmb();
 
 	xdp_ring->xdp_tx_active++;
-	i++;
-	if (i == xdp_ring->count)
-		i = 0;
 
-	tx_bi->next_to_watch = tx_desc;
-	xdp_ring->next_to_use = i;
+	tx_head->next_to_watch = tx_desc;
+	xdp_ring->next_to_use = index;
 
 	return I40E_XDP_TX;
+
+unmap:
+	for (;;) {
+		tx_bi = &xdp_ring->tx_bi[index];
+		if (dma_unmap_len(tx_bi, len))
+			dma_unmap_page(xdp_ring->dev,
+				       dma_unmap_addr(tx_bi, dma),
+				       dma_unmap_len(tx_bi, len),
+				       DMA_TO_DEVICE);
+		dma_unmap_len_set(tx_bi, len, 0);
+		if (tx_bi == tx_head)
+			break;
+
+		if (!index)
+			index += xdp_ring->count;
+		index--;
+	}
+
+	return I40E_XDP_CONSUMED;
 }
 
 /**
-- 
2.35.1