i40e: add xdp_buff to i40e_ring struct

Store xdp_buff on Rx ring struct in preparation for XDP multi-buffer
support. This will allow us to combine fragmented frames across
separate NAPI cycles in the same way as currently skb fragments are
handled. This means that skb pointer on Rx ring will become redundant
and will be removed in a later patch. As a consequence i40e_trace() now
uses xdp instead of skb pointer.

Truesize only needs to be calculated for page sizes bigger than 4k as it
is always half-page for 4k pages. With xdp_buff on ring, frame size can
now be set during xdp_init_buff() and need not be repopulated in each
NAPI call for 4k pages. As a consequence i40e_rx_frame_truesize() is now
used only for bigger pages.
Signed-off-by: Tirthendu Sarkar <tirthendu.sarkar@intel.com>
Tested-by: Chandan Kumar Rout <chandanx.rout@intel.com> (A Contingent Worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/i40e/i40e_main.c

@@ -3616,6 +3616,8 @@ static int i40e_configure_rx_ring(struct i40e_ring *ring)
 		}
 	}
 
+	xdp_init_buff(&ring->xdp, i40e_rx_pg_size(ring) / 2, &ring->xdp_rxq);
+
 	rx_ctx.dbuff = DIV_ROUND_UP(ring->rx_buf_len,
 				    BIT_ULL(I40E_RXQ_CTX_DBUFF_SHIFT));
 

drivers/net/ethernet/intel/i40e/i40e_trace.h

@@ -162,45 +162,45 @@ DECLARE_EVENT_CLASS(
 
 	TP_PROTO(struct i40e_ring *ring,
 		 union i40e_16byte_rx_desc *desc,
-		 struct sk_buff *skb),
+		 struct xdp_buff *xdp),
 
-	TP_ARGS(ring, desc, skb),
+	TP_ARGS(ring, desc, xdp),
 
 	TP_STRUCT__entry(
 		__field(void*, ring)
 		__field(void*, desc)
-		__field(void*, skb)
+		__field(void*, xdp)
 		__string(devname, ring->netdev->name)
 	),
 
 	TP_fast_assign(
 		__entry->ring = ring;
 		__entry->desc = desc;
-		__entry->skb = skb;
+		__entry->xdp = xdp;
 		__assign_str(devname, ring->netdev->name);
 	),
 
 	TP_printk(
-		"netdev: %s ring: %p desc: %p skb %p",
+		"netdev: %s ring: %p desc: %p xdp %p",
 		__get_str(devname), __entry->ring,
-		__entry->desc, __entry->skb)
+		__entry->desc, __entry->xdp)
 );
 
 DEFINE_EVENT(
 	i40e_rx_template, i40e_clean_rx_irq,
 	TP_PROTO(struct i40e_ring *ring,
 		 union i40e_16byte_rx_desc *desc,
-		 struct sk_buff *skb),
+		 struct xdp_buff *xdp),
 
-	TP_ARGS(ring, desc, skb));
+	TP_ARGS(ring, desc, xdp));
 
 DEFINE_EVENT(
 	i40e_rx_template, i40e_clean_rx_irq_rx,
 	TP_PROTO(struct i40e_ring *ring,
 		 union i40e_16byte_rx_desc *desc,
-		 struct sk_buff *skb),
+		 struct xdp_buff *xdp),
 
-	TP_ARGS(ring, desc, skb));
+	TP_ARGS(ring, desc, xdp));
 
 DECLARE_EVENT_CLASS(
 	i40e_xmit_template,

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -1619,21 +1619,19 @@ void i40e_release_rx_desc(struct i40e_ring *rx_ring, u32 val)
 	writel(val, rx_ring->tail);
 }
 
+#if (PAGE_SIZE >= 8192)
 static unsigned int i40e_rx_frame_truesize(struct i40e_ring *rx_ring,
 					   unsigned int size)
 {
 	unsigned int truesize;
 
-#if (PAGE_SIZE < 8192)
-	truesize = i40e_rx_pg_size(rx_ring) / 2; /* Must be power-of-2 */
-#else
 	truesize = rx_ring->rx_offset ?
 		SKB_DATA_ALIGN(size + rx_ring->rx_offset) +
 		SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) :
 		SKB_DATA_ALIGN(size);
-#endif
 	return truesize;
 }
+#endif
 
 /**
  * i40e_alloc_mapped_page - recycle or make a new page
@@ -2405,21 +2403,16 @@ static void i40e_inc_ntp(struct i40e_ring *rx_ring)
 static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget,
 			     unsigned int *rx_cleaned)
 {
-	unsigned int total_rx_bytes = 0, total_rx_packets = 0, frame_sz = 0;
+	unsigned int total_rx_bytes = 0, total_rx_packets = 0;
 	u16 cleaned_count = I40E_DESC_UNUSED(rx_ring);
 	unsigned int offset = rx_ring->rx_offset;
+	struct xdp_buff *xdp = &rx_ring->xdp;
 	struct sk_buff *skb = rx_ring->skb;
 	unsigned int xdp_xmit = 0;
 	struct bpf_prog *xdp_prog;
 	bool failure = false;
-	struct xdp_buff xdp;
 	int xdp_res = 0;
 
-#if (PAGE_SIZE < 8192)
-	frame_sz = i40e_rx_frame_truesize(rx_ring, 0);
-#endif
-	xdp_init_buff(&xdp, frame_sz, &rx_ring->xdp_rxq);
-
 	xdp_prog = READ_ONCE(rx_ring->xdp_prog);
 
 	while (likely(total_rx_packets < (unsigned int)budget)) {
@@ -2467,7 +2460,7 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget,
 		if (!size)
 			break;
 
-		i40e_trace(clean_rx_irq, rx_ring, rx_desc, skb);
+		i40e_trace(clean_rx_irq, rx_ring, rx_desc, xdp);
 		rx_buffer = i40e_get_rx_buffer(rx_ring, size);
 
 		/* retrieve a buffer from the ring */
@@ -2476,19 +2469,19 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget,
 
 			hard_start = page_address(rx_buffer->page) +
 				     rx_buffer->page_offset - offset;
-			xdp_prepare_buff(&xdp, hard_start, offset, size, true);
-			xdp_buff_clear_frags_flag(&xdp);
+			xdp_prepare_buff(xdp, hard_start, offset, size, true);
+			xdp_buff_clear_frags_flag(xdp);
 #if (PAGE_SIZE > 4096)
 			/* At larger PAGE_SIZE, frame_sz depend on len size */
-			xdp.frame_sz = i40e_rx_frame_truesize(rx_ring, size);
+			xdp->frame_sz = i40e_rx_frame_truesize(rx_ring, size);
 #endif
-			xdp_res = i40e_run_xdp(rx_ring, &xdp, xdp_prog);
+			xdp_res = i40e_run_xdp(rx_ring, xdp, xdp_prog);
 		}
 
 		if (xdp_res) {
 			if (xdp_res & (I40E_XDP_TX | I40E_XDP_REDIR)) {
 				xdp_xmit |= xdp_res;
-				i40e_rx_buffer_flip(rx_buffer, xdp.frame_sz);
+				i40e_rx_buffer_flip(rx_buffer, xdp->frame_sz);
 			} else {
 				rx_buffer->pagecnt_bias++;
 			}
@@ -2497,9 +2490,9 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget,
 		} else if (skb) {
 			i40e_add_rx_frag(rx_ring, rx_buffer, skb, size);
 		} else if (ring_uses_build_skb(rx_ring)) {
-			skb = i40e_build_skb(rx_ring, rx_buffer, &xdp);
+			skb = i40e_build_skb(rx_ring, rx_buffer, xdp);
 		} else {
-			skb = i40e_construct_skb(rx_ring, rx_buffer, &xdp);
+			skb = i40e_construct_skb(rx_ring, rx_buffer, xdp);
 		}
 
 		/* exit if we failed to retrieve a buffer */
@@ -2528,7 +2521,7 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget,
 		/* populate checksum, VLAN, and protocol */
 		i40e_process_skb_fields(rx_ring, rx_desc, skb);
 
-		i40e_trace(clean_rx_irq_rx, rx_ring, rx_desc, skb);
+		i40e_trace(clean_rx_irq_rx, rx_ring, rx_desc, xdp);
 		napi_gro_receive(&rx_ring->q_vector->napi, skb);
 		skb = NULL;
 

drivers/net/ethernet/intel/i40e/i40e_txrx.h

@@ -337,6 +337,13 @@ struct i40e_ring {
 	u8 dcb_tc;			/* Traffic class of ring */
 	u8 __iomem *tail;
 
+	/* Storing xdp_buff on ring helps in saving the state of partially built
+	 * packet when i40e_clean_rx_ring_irq() must return before it sees EOP
+	 * and to resume packet building for this ring in the next call to
+	 * i40e_clean_rx_ring_irq().
+	 */
+	struct xdp_buff xdp;
+
 	/* Next descriptor to be processed; next_to_clean is updated only on
 	 * processing EOP descriptor
 	 */