[PATCH RFC v1 05/15] ixgbe: add XDP frame size to driver

[Jesper Dangaard Brouer <brouer@redhat.com>]

The ixgbe driver uses different memory models depending on PAGE_SIZE at
compile time. For PAGE_SIZE 4K it uses page splitting, meaning for
normal MTU frame size is 2048 bytes (and headroom 192 bytes).
For PAGE_SIZE larger than 4K, driver advance its rx_buffer->page_offset
with the frame size "truesize".

When driver enable XDP it uses build_skb() which provides the necessary
tailroom for XDP-redirect.

When XDP frame size doesn't depend on RX packet size (4K case), then
xdp.frame_sz can be updated once outside the main NAPI loop.

Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe.h      |   17 +++++++++++++++++
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |   18 ++++++++++--------
 2 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe.h b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
index 2833e4f041ce..943b643b6ed8 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe.h
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
@@ -417,6 +417,23 @@ static inline unsigned int ixgbe_rx_pg_order(struct ixgbe_ring *ring)
 }
 #define ixgbe_rx_pg_size(_ring) (PAGE_SIZE << ixgbe_rx_pg_order(_ring))
 
+static inline unsigned int ixgbe_rx_frame_truesize(struct ixgbe_ring *rx_ring,
+						   unsigned int size)
+{
+	unsigned int truesize;
+
+#if (PAGE_SIZE < 8192)
+	truesize = ixgbe_rx_pg_size(rx_ring) / 2; /* Must be power-of-2 */
+#else
+	/* Notice XDP must use build_skb() mode */
+	truesize = ring_uses_build_skb(rx_ring) ?
+		SKB_DATA_ALIGN(IXGBE_SKB_PAD + size) +
+		SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) :
+		SKB_DATA_ALIGN(size);
+#endif
+	return truesize;
+}
+
 #define IXGBE_ITR_ADAPTIVE_MIN_INC	2
 #define IXGBE_ITR_ADAPTIVE_MIN_USECS	10
 #define IXGBE_ITR_ADAPTIVE_MAX_USECS	126
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index ea6834bae04c..f505ed8c9dc1 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -2248,16 +2248,10 @@ static void ixgbe_rx_buffer_flip(struct ixgbe_ring *rx_ring,
 				 struct ixgbe_rx_buffer *rx_buffer,
 				 unsigned int size)
 {
+	unsigned int truesize = ixgbe_rx_frame_truesize(rx_ring, size);
 #if (PAGE_SIZE < 8192)
-	unsigned int truesize = ixgbe_rx_pg_size(rx_ring) / 2;
-
 	rx_buffer->page_offset ^= truesize;
 #else
-	unsigned int truesize = ring_uses_build_skb(rx_ring) ?
-				SKB_DATA_ALIGN(IXGBE_SKB_PAD + size) +
-				SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) :
-				SKB_DATA_ALIGN(size);
-
 	rx_buffer->page_offset += truesize;
 #endif
 }
@@ -2291,6 +2285,11 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,
 
 	xdp.rxq = &rx_ring->xdp_rxq;
 
+	/* Frame size depend on rx_ring setup when PAGE_SIZE=4K */
+#if (PAGE_SIZE < 8192)
+	xdp.frame_sz = ixgbe_rx_frame_truesize(rx_ring, 0);
+#endif
+
 	while (likely(total_rx_packets < budget)) {
 		union ixgbe_adv_rx_desc *rx_desc;
 		struct ixgbe_rx_buffer *rx_buffer;
@@ -2324,7 +2323,10 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,
 			xdp.data_hard_start = xdp.data -
 					      ixgbe_rx_offset(rx_ring);
 			xdp.data_end = xdp.data + size;
-
+#if (PAGE_SIZE > 4096)
+			/* At larger PAGE_SIZE, frame_sz depend on size */
+			xdp.frame_sz = ixgbe_rx_frame_truesize(rx_ring, size);
+#endif
 			skb = ixgbe_run_xdp(adapter, rx_ring, &xdp);
 		}