net: ena: use build_skb() in RX path

This patch converts the RX path to use build_skb() for packets larger
than copybreak (set to 256 by default). This function makes the first
descriptor's page to be the linear part of the sk_buff struct buffer.

Also remove the SKB description from the README since most of it no
longer relevant and the parts that are left don't add information.

Signed-off-by: Shay Agroskin <shayagr@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
index b613067..d7bc4f4 100644 (file)
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -529,7 +529,7 @@ static void ena_xdp_exchange_program_rx_in_range(struct ena_adapter *adapter,
                        rx_ring->rx_headroom = XDP_PACKET_HEADROOM;
                } else {
                        ena_xdp_unregister_rxq_info(rx_ring);
-                       rx_ring->rx_headroom = 0;
+                       rx_ring->rx_headroom = NET_SKB_PAD;
                }
        }
 }
@@ -720,6 +720,7 @@ static void ena_init_io_rings(struct ena_adapter *adapter,
                        rxr->smoothed_interval =
                                ena_com_get_nonadaptive_moderation_interval_rx(ena_dev);
                        rxr->empty_rx_queue = 0;
+                       rxr->rx_headroom = NET_SKB_PAD;
                        adapter->ena_napi[i].dim.mode = DIM_CQ_PERIOD_MODE_START_FROM_EQE;
                        rxr->xdp_ring = &adapter->tx_ring[i + adapter->num_io_queues];
                }
@@ -982,6 +983,7 @@ static int ena_alloc_rx_page(struct ena_ring *rx_ring,
        struct ena_com_buf *ena_buf;
        struct page *page;
        dma_addr_t dma;
+       int tailroom;
 
        /* restore page offset value in case it has been changed by device */
        rx_info->page_offset = headroom;
@@ -1012,10 +1014,12 @@ static int ena_alloc_rx_page(struct ena_ring *rx_ring,
        netif_dbg(rx_ring->adapter, rx_status, rx_ring->netdev,
                  "Allocate page %p, rx_info %p\n", page, rx_info);
 
+       tailroom = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+
        rx_info->page = page;
        ena_buf = &rx_info->ena_buf;
        ena_buf->paddr = dma + headroom;
-       ena_buf->len = ENA_PAGE_SIZE - headroom;
+       ena_buf->len = ENA_PAGE_SIZE - headroom - tailroom;
 
        return 0;
 }
@@ -1381,21 +1385,23 @@ static int ena_clean_tx_irq(struct ena_ring *tx_ring, u32 budget)
        return tx_pkts;
 }
 
-static struct sk_buff *ena_alloc_skb(struct ena_ring *rx_ring, bool frags)
+static struct sk_buff *ena_alloc_skb(struct ena_ring *rx_ring, void *first_frag)
 {
        struct sk_buff *skb;
 
-       if (frags)
-               skb = napi_get_frags(rx_ring->napi);
-       else
+       if (!first_frag)
                skb = netdev_alloc_skb_ip_align(rx_ring->netdev,
                                                rx_ring->rx_copybreak);
+       else
+               skb = build_skb(first_frag, ENA_PAGE_SIZE);
 
        if (unlikely(!skb)) {
                ena_increase_stat(&rx_ring->rx_stats.skb_alloc_fail, 1,
                                  &rx_ring->syncp);
+
                netif_dbg(rx_ring->adapter, rx_err, rx_ring->netdev,
-                         "Failed to allocate skb. frags: %d\n", frags);
+                         "Failed to allocate skb. first_frag %s\n",
+                         first_frag ? "provided" : "not provided");
                return NULL;
        }
 
@@ -1410,7 +1416,9 @@ static struct sk_buff *ena_rx_skb(struct ena_ring *rx_ring,
        struct sk_buff *skb;
        struct ena_rx_buffer *rx_info;
        u16 len, req_id, buf = 0;
-       void *va;
+       void *page_addr;
+       u32 page_offset;
+       void *data_addr;
 
        len = ena_bufs[buf].len;
        req_id = ena_bufs[buf].req_id;
@@ -1428,12 +1436,14 @@ static struct sk_buff *ena_rx_skb(struct ena_ring *rx_ring,
                  rx_info, rx_info->page);
 
        /* save virt address of first buffer */
-       va = page_address(rx_info->page) + rx_info->page_offset;
+       page_addr = page_address(rx_info->page);
+       page_offset = rx_info->page_offset;
+       data_addr = page_addr + page_offset;
 
-       prefetch(va);
+       prefetch(data_addr);
 
        if (len <= rx_ring->rx_copybreak) {
-               skb = ena_alloc_skb(rx_ring, false);
+               skb = ena_alloc_skb(rx_ring, NULL);
                if (unlikely(!skb))
                        return NULL;
 
@@ -1446,7 +1456,7 @@ static struct sk_buff *ena_rx_skb(struct ena_ring *rx_ring,
                                        dma_unmap_addr(&rx_info->ena_buf, paddr),
                                        len,
                                        DMA_FROM_DEVICE);
-               skb_copy_to_linear_data(skb, va, len);
+               skb_copy_to_linear_data(skb, data_addr, len);
                dma_sync_single_for_device(rx_ring->dev,
                                           dma_unmap_addr(&rx_info->ena_buf, paddr),
                                           len,
@@ -1460,16 +1470,18 @@ static struct sk_buff *ena_rx_skb(struct ena_ring *rx_ring,
                return skb;
        }
 
-       skb = ena_alloc_skb(rx_ring, true);
+       ena_unmap_rx_buff(rx_ring, rx_info);
+
+       skb = ena_alloc_skb(rx_ring, page_addr);
        if (unlikely(!skb))
                return NULL;
 
-       do {
-               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);
+       /* Populate skb's linear part */
+       skb_reserve(skb, page_offset);
+       skb_put(skb, len);
+       skb->protocol = eth_type_trans(skb, rx_ring->netdev);
 
+       do {
                netif_dbg(rx_ring->adapter, rx_status, rx_ring->netdev,
                          "RX skb updated. len %d. data_len %d\n",
                          skb->len, skb->data_len);
@@ -1488,6 +1500,12 @@ static struct sk_buff *ena_rx_skb(struct ena_ring *rx_ring,
                req_id = ena_bufs[buf].req_id;
 
                rx_info = &rx_ring->rx_buffer_info[req_id];
+
+               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);
+
        } while (1);
 
        return skb;
@@ -1700,14 +1718,12 @@ static int ena_clean_rx_irq(struct ena_ring *rx_ring, struct napi_struct *napi,
 
                skb_record_rx_queue(skb, rx_ring->qid);
 
-               if (rx_ring->ena_bufs[0].len <= rx_ring->rx_copybreak) {
-                       total_len += rx_ring->ena_bufs[0].len;
+               if (rx_ring->ena_bufs[0].len <= rx_ring->rx_copybreak)
                        rx_copybreak_pkt++;
-                       napi_gro_receive(napi, skb);
-               } else {
-                       total_len += skb->len;
-                       napi_gro_frags(napi);
-               }
+
+               total_len += skb->len;
+
+               napi_gro_receive(napi, skb);
 
                res_budget--;
        } while (likely(res_budget));