ice: make RX hash reading code more reusable

Previously, we only needed RX hash in skb path,
hence all related code was written with skb in mind.
But with the addition of XDP hints via kfuncs to the ice driver,
the same logic will be needed in .xmo_() callbacks.

Separate generic process of reading RX hash from a descriptor
into a separate function.
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
Link: https://lore.kernel.org/r/20231205210847.28460-2-larysa.zaremba@intel.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

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

@@ -63,28 +63,42 @@ static enum pkt_hash_types ice_ptype_to_htype(u16 ptype)
 }
 
 /**
- * ice_rx_hash - set the hash value in the skb
+ * ice_get_rx_hash - get RX hash value from descriptor
+ * @rx_desc: specific descriptor
+ *
+ * Returns hash, if present, 0 otherwise.
+ */
+static u32 ice_get_rx_hash(const union ice_32b_rx_flex_desc *rx_desc)
+{
+	const struct ice_32b_rx_flex_desc_nic *nic_mdid;
+
+	if (unlikely(rx_desc->wb.rxdid != ICE_RXDID_FLEX_NIC))
+		return 0;
+
+	nic_mdid = (struct ice_32b_rx_flex_desc_nic *)rx_desc;
+	return le32_to_cpu(nic_mdid->rss_hash);
+}
+
+/**
+ * ice_rx_hash_to_skb - set the hash value in the skb
  * @rx_ring: descriptor ring
  * @rx_desc: specific descriptor
  * @skb: pointer to current skb
  * @rx_ptype: the ptype value from the descriptor
  */
 static void
-ice_rx_hash(struct ice_rx_ring *rx_ring, union ice_32b_rx_flex_desc *rx_desc,
-	    struct sk_buff *skb, u16 rx_ptype)
+ice_rx_hash_to_skb(const struct ice_rx_ring *rx_ring,
+		   const union ice_32b_rx_flex_desc *rx_desc,
+		   struct sk_buff *skb, u16 rx_ptype)
 {
-	struct ice_32b_rx_flex_desc_nic *nic_mdid;
 	u32 hash;
 
 	if (!(rx_ring->netdev->features & NETIF_F_RXHASH))
 		return;
 
-	if (rx_desc->wb.rxdid != ICE_RXDID_FLEX_NIC)
-		return;
-
-	nic_mdid = (struct ice_32b_rx_flex_desc_nic *)rx_desc;
-	hash = le32_to_cpu(nic_mdid->rss_hash);
-	skb_set_hash(skb, hash, ice_ptype_to_htype(rx_ptype));
+	hash = ice_get_rx_hash(rx_desc);
+	if (likely(hash))
+		skb_set_hash(skb, hash, ice_ptype_to_htype(rx_ptype));
 }
 
 /**
@@ -186,7 +200,7 @@ ice_process_skb_fields(struct ice_rx_ring *rx_ring,
 		       union ice_32b_rx_flex_desc *rx_desc,
 		       struct sk_buff *skb, u16 ptype)
 {
-	ice_rx_hash(rx_ring, rx_desc, skb, ptype);
+	ice_rx_hash_to_skb(rx_ring, rx_desc, skb, ptype);
 
 	/* modifies the skb - consumes the enet header */
 	skb->protocol = eth_type_trans(skb, rx_ring->netdev);