ice: Micro-optimize .ndo_xdp_xmit() path

After the recent mbuf changes, ice_xmit_xdp_ring() became a 3-liner.
It makes no sense to keep it global in a different file than its caller.
Move it just next to the sole call site and mark static. Also, it
doesn't need a full xdp_convert_frame_to_buff(). Save several cycles
and fill only the fields used by __ice_xmit_xdp_ring() later on.
Finally, since it doesn't modify @xdpf anyhow, mark the argument const
to save some more (whole -11 bytes of .text! :D).

Thanks to 1 jump less and less calcs as well, this yields as many as
6.7 Mpps per queue. `xdp.data_hard_start = xdpf` is fully intentional
again (see xdp_convert_buff_to_frame()) and just works when there are
no source device's driver issues.

Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/bpf/20230210170618.1973430-7-alexandr.lobakin@intel.com

drivers/net/ethernet/intel/ice/ice_txrx.c

@@ -605,6 +605,25 @@ ice_run_xdp(struct ice_rx_ring *rx_ring, struct xdp_buff *xdp,
 		ice_set_rx_bufs_act(xdp, rx_ring, ret);
 }
 
+/**
+ * ice_xmit_xdp_ring - submit frame to XDP ring for transmission
+ * @xdpf: XDP frame that will be converted to XDP buff
+ * @xdp_ring: XDP ring for transmission
+ */
+static int ice_xmit_xdp_ring(const struct xdp_frame *xdpf,
+			     struct ice_tx_ring *xdp_ring)
+{
+	struct xdp_buff xdp;
+
+	xdp.data_hard_start = (void *)xdpf;
+	xdp.data = xdpf->data;
+	xdp.data_end = xdp.data + xdpf->len;
+	xdp.frame_sz = xdpf->frame_sz;
+	xdp.flags = xdpf->flags;
+
+	return __ice_xmit_xdp_ring(&xdp, xdp_ring, true);
+}
+
 /**
  * ice_xdp_xmit - submit packets to XDP ring for transmission
  * @dev: netdev
@@ -650,7 +669,7 @@ ice_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames,
 
 	tx_buf = &xdp_ring->tx_buf[xdp_ring->next_to_use];
 	for (i = 0; i < n; i++) {
-		struct xdp_frame *xdpf = frames[i];
+		const struct xdp_frame *xdpf = frames[i];
 		int err;
 
 		err = ice_xmit_xdp_ring(xdpf, xdp_ring);

drivers/net/ethernet/intel/ice/ice_txrx_lib.c

@@ -434,19 +434,6 @@ int __ice_xmit_xdp_ring(struct xdp_buff *xdp, struct ice_tx_ring *xdp_ring,
 	return ICE_XDP_CONSUMED;
 }
 
-/**
- * ice_xmit_xdp_ring - submit frame to XDP ring for transmission
- * @xdpf: XDP frame that will be converted to XDP buff
- * @xdp_ring: XDP ring for transmission
- */
-int ice_xmit_xdp_ring(struct xdp_frame *xdpf, struct ice_tx_ring *xdp_ring)
-{
-	struct xdp_buff xdp;
-
-	xdp_convert_frame_to_buff(xdpf, &xdp);
-	return __ice_xmit_xdp_ring(&xdp, xdp_ring, true);
-}
-
 /**
  * ice_finalize_xdp_rx - Bump XDP Tx tail and/or flush redirect map
  * @xdp_ring: XDP ring

drivers/net/ethernet/intel/ice/ice_txrx_lib.h

@@ -142,7 +142,6 @@ static inline u32 ice_set_rs_bit(const struct ice_tx_ring *xdp_ring)
 
 void ice_finalize_xdp_rx(struct ice_tx_ring *xdp_ring, unsigned int xdp_res, u32 first_idx);
 int ice_xmit_xdp_buff(struct xdp_buff *xdp, struct ice_tx_ring *xdp_ring);
-int ice_xmit_xdp_ring(struct xdp_frame *xdpf, struct ice_tx_ring *xdp_ring);
 int __ice_xmit_xdp_ring(struct xdp_buff *xdp, struct ice_tx_ring *xdp_ring,
 			bool frame);
 void ice_release_rx_desc(struct ice_rx_ring *rx_ring, u16 val);