net: ena: introduce XDP redirect implementation

This patch adds a partial support for the XDP_REDIRECT directive which
instructs the driver to pass the packet to an interface specified by the
program. The directive is passed to the driver by calling bpf_redirect()
or bpf_redirect_map() functions from the eBPF program.

To lay the ground for integration with the existing XDP TX
implementation the patch removes the redundant page ref count increase
in ena_xdp_xmit_frame() and then decrease in ena_clean_rx_irq(). Instead
it only DMA unmaps descriptors for which XDP TX or REDIRECT directive
was received.

The XDP Redirect support is still missing .ndo_xdp_xmit function
implementation, which allows to redirect packet to an ENA interface,
which would be added in a later patch.
Signed-off-by: Shay Agroskin <shayagr@amazon.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/amazon/ena/ena_ethtool.c

@@ -95,6 +95,7 @@ static const struct ena_stats ena_stats_rx_strings[] = {
 	ENA_STAT_RX_ENTRY(xdp_pass),
 	ENA_STAT_RX_ENTRY(xdp_tx),
 	ENA_STAT_RX_ENTRY(xdp_invalid),
+	ENA_STAT_RX_ENTRY(xdp_redirect),
 };
 
 static const struct ena_stats ena_stats_ena_com_strings[] = {

drivers/net/ethernet/amazon/ena/ena_netdev.c

@@ -289,21 +289,17 @@ static int ena_xdp_xmit_frame(struct net_device *dev,
 	struct ena_com_tx_ctx ena_tx_ctx = {};
 	struct ena_tx_buffer *tx_info;
 	struct ena_ring *xdp_ring;
-	struct page *rx_buff_page;
 	u16 next_to_use, req_id;
 	int rc;
 	void *push_hdr;
 	u32 push_len;
 
-	rx_buff_page = virt_to_page(xdpf->data);
-
 	xdp_ring = &adapter->tx_ring[qid];
 	next_to_use = xdp_ring->next_to_use;
 	req_id = xdp_ring->free_ids[next_to_use];
 	tx_info = &xdp_ring->tx_buffer_info[req_id];
 	tx_info->num_of_bufs = 0;
-	page_ref_inc(rx_buff_page);
-	tx_info->xdp_rx_page = rx_buff_page;
+	tx_info->xdp_rx_page = virt_to_page(xdpf->data);
 
 	rc = ena_xdp_tx_map_frame(xdp_ring, tx_info, xdpf, &push_hdr, &push_len);
 	if (unlikely(rc))
@@ -335,7 +331,7 @@ static int ena_xdp_xmit_frame(struct net_device *dev,
 	ena_unmap_tx_buff(xdp_ring, tx_info);
 	tx_info->xdpf = NULL;
 error_drop_packet:
-	__free_page(tx_info->xdp_rx_page);
+	xdp_return_frame(xdpf);
 	return NETDEV_TX_OK;
 }
 
@@ -354,25 +350,36 @@ static int ena_xdp_execute(struct ena_ring *rx_ring, struct xdp_buff *xdp)
 
 	verdict = bpf_prog_run_xdp(xdp_prog, xdp);
 
-	if (verdict == XDP_TX) {
+	switch (verdict) {
+	case XDP_TX:
 		xdpf = xdp_convert_buff_to_frame(xdp);
 		if (unlikely(!xdpf)) {
 			trace_xdp_exception(rx_ring->netdev, xdp_prog, verdict);
 			xdp_stat = &rx_ring->rx_stats.xdp_aborted;
-		} else {
-			ena_xdp_xmit_frame(rx_ring->netdev, xdpf,
-					   rx_ring->qid + rx_ring->adapter->num_io_queues);
+			break;
+		}
 
-			xdp_stat = &rx_ring->rx_stats.xdp_tx;
+		ena_xdp_xmit_frame(rx_ring->netdev, xdpf,
+				   rx_ring->qid + rx_ring->adapter->num_io_queues);
+		xdp_stat = &rx_ring->rx_stats.xdp_tx;
+		break;
+	case XDP_REDIRECT:
+		if (likely(!xdp_do_redirect(rx_ring->netdev, xdp, xdp_prog))) {
+			xdp_stat = &rx_ring->rx_stats.xdp_redirect;
+			break;
 		}
-	} else if (unlikely(verdict == XDP_ABORTED)) {
+		fallthrough;
+	case XDP_ABORTED:
 		trace_xdp_exception(rx_ring->netdev, xdp_prog, verdict);
 		xdp_stat = &rx_ring->rx_stats.xdp_aborted;
-	} else if (unlikely(verdict == XDP_DROP)) {
+		break;
+	case XDP_DROP:
 		xdp_stat = &rx_ring->rx_stats.xdp_drop;
-	} else if (unlikely(verdict == XDP_PASS)) {
+		break;
+	case XDP_PASS:
 		xdp_stat = &rx_ring->rx_stats.xdp_pass;
-	} else {
+		break;
+	default:
 		bpf_warn_invalid_xdp_action(verdict);
 		xdp_stat = &rx_ring->rx_stats.xdp_invalid;
 	}
@@ -958,11 +965,20 @@ static int ena_alloc_rx_page(struct ena_ring *rx_ring,
 	return 0;
 }
 
+static void ena_unmap_rx_buff(struct ena_ring *rx_ring,
+			      struct ena_rx_buffer *rx_info)
+{
+	struct ena_com_buf *ena_buf = &rx_info->ena_buf;
+
+	dma_unmap_page(rx_ring->dev, ena_buf->paddr - rx_ring->rx_headroom,
+		       ENA_PAGE_SIZE,
+		       DMA_BIDIRECTIONAL);
+}
+
 static void ena_free_rx_page(struct ena_ring *rx_ring,
 			     struct ena_rx_buffer *rx_info)
 {
 	struct page *page = rx_info->page;
-	struct ena_com_buf *ena_buf = &rx_info->ena_buf;
 
 	if (unlikely(!page)) {
 		netif_warn(rx_ring->adapter, rx_err, rx_ring->netdev,
@@ -970,9 +986,7 @@ static void ena_free_rx_page(struct ena_ring *rx_ring,
 		return;
 	}
 
-	dma_unmap_page(rx_ring->dev, ena_buf->paddr - rx_ring->rx_headroom,
-		       ENA_PAGE_SIZE,
-		       DMA_BIDIRECTIONAL);
+	ena_unmap_rx_buff(rx_ring, rx_info);
 
 	__free_page(page);
 	rx_info->page = NULL;
@@ -1396,9 +1410,7 @@ static struct sk_buff *ena_rx_skb(struct ena_ring *rx_ring,
 		return NULL;
 
 	do {
-		dma_unmap_page(rx_ring->dev,
-			       dma_unmap_addr(&rx_info->ena_buf, paddr),
-			       ENA_PAGE_SIZE, DMA_BIDIRECTIONAL);
+		ena_unmap_rx_buff(rx_ring, rx_info);
 
 		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, rx_info->page,
 				rx_info->page_offset, len, ENA_PAGE_SIZE);
@@ -1556,6 +1568,7 @@ static int ena_clean_rx_irq(struct ena_ring *rx_ring, struct napi_struct *napi,
 	struct sk_buff *skb;
 	int refill_required;
 	struct xdp_buff xdp;
+	int xdp_flags = 0;
 	int total_len = 0;
 	int xdp_verdict;
 	int rc = 0;
@@ -1603,22 +1616,25 @@ static int ena_clean_rx_irq(struct ena_ring *rx_ring, struct napi_struct *napi,
 					 &next_to_clean);
 
 		if (unlikely(!skb)) {
-			/* The page might not actually be freed here since the
-			 * page reference count is incremented in
-			 * ena_xdp_xmit_frame(), and it will be decreased only
-			 * when send completion was received from the device
-			 */
-			if (xdp_verdict == XDP_TX)
-				ena_free_rx_page(rx_ring,
-						 &rx_ring->rx_buffer_info[rx_ring->ena_bufs[0].req_id]);
 			for (i = 0; i < ena_rx_ctx.descs; i++) {
-				rx_ring->free_ids[next_to_clean] =
-					rx_ring->ena_bufs[i].req_id;
+				int req_id = rx_ring->ena_bufs[i].req_id;
+
+				rx_ring->free_ids[next_to_clean] = req_id;
 				next_to_clean =
 					ENA_RX_RING_IDX_NEXT(next_to_clean,
 							     rx_ring->ring_size);
+
+				/* Packets was passed for transmission, unmap it
+				 * from RX side.
+				 */
+				if (xdp_verdict == XDP_TX || xdp_verdict == XDP_REDIRECT) {
+					ena_unmap_rx_buff(rx_ring,
+							  &rx_ring->rx_buffer_info[req_id]);
+					rx_ring->rx_buffer_info[req_id].page = NULL;
+				}
 			}
 			if (xdp_verdict != XDP_PASS) {
+				xdp_flags |= xdp_verdict;
 				res_budget--;
 				continue;
 			}
@@ -1664,6 +1680,9 @@ static int ena_clean_rx_irq(struct ena_ring *rx_ring, struct napi_struct *napi,
 		ena_refill_rx_bufs(rx_ring, refill_required);
 	}
 
+	if (xdp_flags & XDP_REDIRECT)
+		xdp_do_flush_map();
+
 	return work_done;
 
 error:

drivers/net/ethernet/amazon/ena/ena_netdev.h

@@ -239,6 +239,7 @@ struct ena_stats_rx {
 	u64 xdp_pass;
 	u64 xdp_tx;
 	u64 xdp_invalid;
+	u64 xdp_redirect;
 };
 
 struct ena_ring {