gve: Reduce alloc and copy costs in the GQ rx path

Previously, even if just one of the many fragments of a 9k packet
required a copy, we'd copy the whole packet into a freshly-allocated
9k-sized linear SKB, and this led to performance issues.

By having a pool of pages to copy into, each fragment can be
independently handled, leading to a reduced incidence of
allocation and copy.

Signed-off-by: Shailend Chand <shailend@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/google/gve/gve.h

@@ -60,7 +60,8 @@ struct gve_rx_slot_page_info {
 	void *page_address;
 	u32 page_offset; /* offset to write to in page */
 	int pagecnt_bias; /* expected pagecnt if only the driver has a ref */
-	u8 can_flip;
+	u16 pad; /* adjustment for rx padding */
+	u8 can_flip; /* tracks if the networking stack is using the page */
 };
 
 /* A list of pages registered with the device during setup and used by a queue
@@ -149,10 +150,17 @@ struct gve_rx_ctx {
 	/* head and tail of skb chain for the current packet or NULL if none */
 	struct sk_buff *skb_head;
 	struct sk_buff *skb_tail;
-	u16 total_expected_size;
-	u8 expected_frag_cnt;
-	u8 curr_frag_cnt;
-	u8 reuse_frags;
+	u32 total_size;
+	u8 frag_cnt;
+	bool drop_pkt;
+};
+
+struct gve_rx_cnts {
+	u32 ok_pkt_bytes;
+	u16 ok_pkt_cnt;
+	u16 total_pkt_cnt;
+	u16 cont_pkt_cnt;
+	u16 desc_err_pkt_cnt;
 };
 
 /* Contains datapath state used to represent an RX queue. */
@@ -167,6 +175,10 @@ struct gve_rx_ring {
 			/* threshold for posting new buffs and descs */
 			u32 db_threshold;
 			u16 packet_buffer_size;
+
+			u32 qpl_copy_pool_mask;
+			u32 qpl_copy_pool_head;
+			struct gve_rx_slot_page_info *qpl_copy_pool;
 		};
 
 		/* DQO fields. */
@@ -216,7 +228,9 @@ struct gve_rx_ring {
 	u64 rx_desc_err_dropped_pkt; /* free-running count of packets dropped by descriptor error */
 	u64 rx_cont_packet_cnt; /* free-running multi-fragment packets received */
 	u64 rx_frag_flip_cnt; /* free-running count of rx segments where page_flip was used */
-	u64 rx_frag_copy_cnt; /* free-running count of rx segments copied into skb linear portion */
+	u64 rx_frag_copy_cnt; /* free-running count of rx segments copied */
+	u64 rx_frag_alloc_cnt; /* free-running count of rx page allocations */
+
 	u32 q_num; /* queue index */
 	u32 ntfy_id; /* notification block index */
 	struct gve_queue_resources *q_resources; /* head and tail pointer idx */

drivers/net/ethernet/google/gve/gve_ethtool.c

@@ -45,6 +45,7 @@ static const char gve_gstrings_main_stats[][ETH_GSTRING_LEN] = {
 static const char gve_gstrings_rx_stats[][ETH_GSTRING_LEN] = {
 	"rx_posted_desc[%u]", "rx_completed_desc[%u]", "rx_consumed_desc[%u]", "rx_bytes[%u]",
 	"rx_cont_packet_cnt[%u]", "rx_frag_flip_cnt[%u]", "rx_frag_copy_cnt[%u]",
+	"rx_frag_alloc_cnt[%u]",
 	"rx_dropped_pkt[%u]", "rx_copybreak_pkt[%u]", "rx_copied_pkt[%u]",
 	"rx_queue_drop_cnt[%u]", "rx_no_buffers_posted[%u]",
 	"rx_drops_packet_over_mru[%u]", "rx_drops_invalid_checksum[%u]",
@@ -271,6 +272,7 @@ gve_get_ethtool_stats(struct net_device *netdev,
 			data[i++] = rx->rx_cont_packet_cnt;
 			data[i++] = rx->rx_frag_flip_cnt;
 			data[i++] = rx->rx_frag_copy_cnt;
+			data[i++] = rx->rx_frag_alloc_cnt;
 			/* rx dropped packets */
 			data[i++] = tmp_rx_skb_alloc_fail +
 				tmp_rx_buf_alloc_fail +