ice: remove legacy Rx and construct SKB

The commit 53844673d555 ("iavf: kill 'legacy-rx' for good") removed
the legacy Rx path in the iavf driver. This change applies the same
rationale to the ice driver.

The legacy Rx path relied on manual skb allocation and header copying,
which has become increasingly inefficient and difficult to maintain.
With the stabilization of build_skb() and the growing adoption of
features like XDP, page_pool, and multi-buffer support, the legacy
approach is no longer viable.

Key drawbacks of the legacy path included:
- Higher memory pressure due to direct page allocations and splitting;
- Redundant memcpy() operations for packet headers;
- CPU overhead from eth_get_headlen() and Flow Dissector usage;
- Compatibility issues with XDP, which imposes strict headroom and
  tailroom requirements.

The ice driver, like iavf, does not benefit from the minimal headroom
savings that legacy Rx once offered, as it already splits pages into
fixed halves. Removing this path simplifies the Rx logic, eliminates
unnecessary branches in the hotpath, and prepares the driver for
upcoming enhancements.

In addition to removing the legacy Rx path, this change also eliminates
the custom construct_skb() functions from both the standard and
zero-copy (ZC) Rx paths. These are replaced with the build_skb()
and standardized xdp_build_skb_from_zc() helpers, aligning the driver
with the modern XDP infrastructure and reducing code duplication.

This cleanup also reduces code complexity and improves maintainability
as we move toward a more unified and modern Rx model across drivers.

Co-developed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Michal Kubiak <michal.kubiak@intel.com>
Tested-by: Alexander Nowlin <alexander.nowlin@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

1 files changed, 0 insertions, 16 deletions

diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.h b/drivers/net/ethernet/intel/ice/ice_txrx.h
index 841a07bfba54..427f672fe053 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx.h
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.h
@@ -373,7 +373,6 @@ struct ice_rx_ring {
 	dma_addr_t dma;			/* physical address of ring */
 	u8 dcb_tc;			/* Traffic class of ring */
 	u8 ptp_rx;
-#define ICE_RX_FLAGS_RING_BUILD_SKB	BIT(1)
 #define ICE_RX_FLAGS_CRC_STRIP_DIS	BIT(2)
 #define ICE_RX_FLAGS_MULTIDEV		BIT(3)
 #define ICE_RX_FLAGS_RING_GCS		BIT(4)
@@ -422,21 +421,6 @@ struct ice_tx_ring {
 	u16 quanta_prof_id;
 } ____cacheline_internodealigned_in_smp;
 
-static inline bool ice_ring_uses_build_skb(struct ice_rx_ring *ring)
-{
-	return !!(ring->flags & ICE_RX_FLAGS_RING_BUILD_SKB);
-}
-
-static inline void ice_set_ring_build_skb_ena(struct ice_rx_ring *ring)
-{
-	ring->flags |= ICE_RX_FLAGS_RING_BUILD_SKB;
-}
-
-static inline void ice_clear_ring_build_skb_ena(struct ice_rx_ring *ring)
-{
-	ring->flags &= ~ICE_RX_FLAGS_RING_BUILD_SKB;
-}
-
 static inline bool ice_ring_ch_enabled(struct ice_tx_ring *ring)
 {
 	return !!ring->ch;