ice: Introduce ice_xdp_buff

In order to use XDP hints via kfuncs we need to put
RX descriptor and miscellaneous data next to xdp_buff.
Same as in hints implementations in other drivers, we achieve
this through putting xdp_buff into a child structure.

Currently, xdp_buff is stored in the ring structure,
so replace it with union that includes child structure.
This way enough memory is available while existing XDP code
remains isolated from hints.

Minimum size of the new child structure (ice_xdp_buff) is exactly
64 bytes (single cache line). To place it at the start of a cache line,
move 'next' field from CL1 to CL4, as it isn't used often. This still
leaves 192 bits available in CL3 for packet context extensions.
Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/r/20231205210847.28460-5-larysa.zaremba@intel.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

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

@@ -557,13 +557,14 @@ ice_rx_frame_truesize(struct ice_rx_ring *rx_ring, const unsigned int size)
  * @xdp_prog: XDP program to run
  * @xdp_ring: ring to be used for XDP_TX action
  * @rx_buf: Rx buffer to store the XDP action
+ * @eop_desc: Last descriptor in packet to read metadata from
  *
  * Returns any of ICE_XDP_{PASS, CONSUMED, TX, REDIR}
  */
 static void
 ice_run_xdp(struct ice_rx_ring *rx_ring, struct xdp_buff *xdp,
 	    struct bpf_prog *xdp_prog, struct ice_tx_ring *xdp_ring,
-	    struct ice_rx_buf *rx_buf)
+	    struct ice_rx_buf *rx_buf, union ice_32b_rx_flex_desc *eop_desc)
 {
 	unsigned int ret = ICE_XDP_PASS;
 	u32 act;
@@ -571,6 +572,8 @@ ice_run_xdp(struct ice_rx_ring *rx_ring, struct xdp_buff *xdp,
 	if (!xdp_prog)
 		goto exit;
 
+	ice_xdp_meta_set_desc(xdp, eop_desc);
+
 	act = bpf_prog_run_xdp(xdp_prog, xdp);
 	switch (act) {
 	case XDP_PASS:
@@ -1240,7 +1243,7 @@ int ice_clean_rx_irq(struct ice_rx_ring *rx_ring, int budget)
 		if (ice_is_non_eop(rx_ring, rx_desc))
 			continue;
 
-		ice_run_xdp(rx_ring, xdp, xdp_prog, xdp_ring, rx_buf);
+		ice_run_xdp(rx_ring, xdp, xdp_prog, xdp_ring, rx_buf, rx_desc);
 		if (rx_buf->act == ICE_XDP_PASS)
 			goto construct_skb;
 		total_rx_bytes += xdp_get_buff_len(xdp);

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

@@ -257,6 +257,14 @@ enum ice_rx_dtype {
 	ICE_RX_DTYPE_SPLIT_ALWAYS	= 2,
 };
 
+struct ice_xdp_buff {
+	struct xdp_buff xdp_buff;
+	const union ice_32b_rx_flex_desc *eop_desc;
+};
+
+/* Required for compatibility with xdp_buffs from xsk_pool */
+static_assert(offsetof(struct ice_xdp_buff, xdp_buff) == 0);
+
 /* indices into GLINT_ITR registers */
 #define ICE_RX_ITR	ICE_IDX_ITR0
 #define ICE_TX_ITR	ICE_IDX_ITR1
@@ -298,7 +306,6 @@ enum ice_dynamic_itr {
 /* descriptor ring, associated with a VSI */
 struct ice_rx_ring {
 	/* CL1 - 1st cacheline starts here */
-	struct ice_rx_ring *next;	/* pointer to next ring in q_vector */
 	void *desc;			/* Descriptor ring memory */
 	struct device *dev;		/* Used for DMA mapping */
 	struct net_device *netdev;	/* netdev ring maps to */
@@ -310,12 +317,16 @@ struct ice_rx_ring {
 	u16 count;			/* Number of descriptors */
 	u16 reg_idx;			/* HW register index of the ring */
 	u16 next_to_alloc;
-	/* CL2 - 2nd cacheline starts here */
+
 	union {
 		struct ice_rx_buf *rx_buf;
 		struct xdp_buff **xdp_buf;
 	};
+	/* CL2 - 2nd cacheline starts here */
+	union {
+		struct ice_xdp_buff xdp_ext;
 		struct xdp_buff xdp;
+	};
 	/* CL3 - 3rd cacheline starts here */
 	struct bpf_prog *xdp_prog;
 	u16 rx_offset;
@@ -332,6 +343,7 @@ struct ice_rx_ring {
 	/* CL4 - 4th cacheline starts here */
 	struct ice_channel *ch;
 	struct ice_tx_ring *xdp_ring;
+	struct ice_rx_ring *next;	/* pointer to next ring in q_vector */
 	struct xsk_buff_pool *xsk_pool;
 	dma_addr_t dma;			/* physical address of ring */
 	u64 cached_phctime;

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

@@ -151,4 +151,14 @@ ice_process_skb_fields(struct ice_rx_ring *rx_ring,
 		       struct sk_buff *skb);
 void
 ice_receive_skb(struct ice_rx_ring *rx_ring, struct sk_buff *skb, u16 vlan_tag);
+
+static inline void
+ice_xdp_meta_set_desc(struct xdp_buff *xdp,
+		      union ice_32b_rx_flex_desc *eop_desc)
+{
+	struct ice_xdp_buff *xdp_ext = container_of(xdp, struct ice_xdp_buff,
+						    xdp_buff);
+
+	xdp_ext->eop_desc = eop_desc;
+}
 #endif /* !_ICE_TXRX_LIB_H_ */