gve: Implement packet continuation for RX.

This enables the driver to receive RX packets spread across multiple
buffers:

For a given multi-fragment packet the "packet continuation" bit is set
on all descriptors except the last one. These descriptors' payloads are
combined into a single SKB before the SKB is handed to the
networking stack.

This change adds a "packet buffer size" notion for RX queues. The
CreateRxQueue AdminQueue command sent to the device now includes the
packet_buffer_size.

We opt for a packet_buffer_size of PAGE_SIZE / 2 to give the
driver the opportunity to flip pages where we can instead of copying.

Signed-off-by: David Awogbemila <awogbemila@google.com>
Signed-off-by: Jeroen de Borst <jeroendb@google.com>
Reviewed-by: Catherine Sullivan <csully@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 11 deletions

diff --git a/drivers/net/ethernet/google/gve/gve_utils.c b/drivers/net/ethernet/google/gve/gve_utils.c
index 45ff7a9ab5f9..88ca49cbc1e2 100644
--- a/drivers/net/ethernet/google/gve/gve_utils.c
+++ b/drivers/net/ethernet/google/gve/gve_utils.c
@@ -50,20 +50,31 @@ void gve_rx_add_to_block(struct gve_priv *priv, int queue_idx)
 
 struct sk_buff *gve_rx_copy(struct net_device *dev, struct napi_struct *napi,
 			    struct gve_rx_slot_page_info *page_info, u16 len,
-			    u16 pad)
+			    u16 padding, struct gve_rx_ctx *ctx)
 {
-	struct sk_buff *skb = napi_alloc_skb(napi, len);
-	void *va = page_info->page_address + pad +
-		   page_info->page_offset;
-
-	if (unlikely(!skb))
-		return NULL;
-
+	void *va = page_info->page_address + padding + page_info->page_offset;
+	int skb_linear_offset = 0;
+	bool set_protocol = false;
+	struct sk_buff *skb;
+
+	if (ctx) {
+		if (!ctx->skb_head)
+			ctx->skb_head = napi_alloc_skb(napi, ctx->total_expected_size);
+
+		if (unlikely(!ctx->skb_head))
+			return NULL;
+		skb = ctx->skb_head;
+		skb_linear_offset = skb->len;
+		set_protocol = ctx->curr_frag_cnt == ctx->expected_frag_cnt - 1;
+	} else {
+		skb = napi_alloc_skb(napi, len);
+		set_protocol = true;
+	}
 	__skb_put(skb, len);
+	skb_copy_to_linear_data_offset(skb, skb_linear_offset, va, len);
 
-	skb_copy_to_linear_data(skb, va, len);
-
-	skb->protocol = eth_type_trans(skb, dev);
+	if (set_protocol)
+		skb->protocol = eth_type_trans(skb, dev);
 
 	return skb;
 }