nfp: bpf: read from packet data cache for PTR_TO_PACKET

This patch assumes there is a packet data cache, and would try to read
packet data from the cache instead of from memory.

This patch only implements the optimisation "backend", it doesn't build
the packet data cache, so this optimisation is not enabled.

This patch has only enabled aligned packet data read, i.e. when the read
offset to the start of cache is REG_WIDTH aligned.

Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

drivers/net/ethernet/netronome/nfp/bpf/jit.c

@@ -1838,6 +1838,74 @@ mem_ldx_emem(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 					 tmp_reg, meta->insn.dst_reg * 2, size);
 }
 
+static void
+mem_ldx_data_init_pktcache(struct nfp_prog *nfp_prog,
+			   struct nfp_insn_meta *meta)
+{
+	s16 range_start = meta->pkt_cache.range_start;
+	s16 range_end = meta->pkt_cache.range_end;
+	swreg src_base, off;
+	u8 xfer_num, len;
+	bool indir;
+
+	off = re_load_imm_any(nfp_prog, range_start, imm_b(nfp_prog));
+	src_base = reg_a(meta->insn.src_reg * 2);
+	len = range_end - range_start;
+	xfer_num = round_up(len, REG_WIDTH) / REG_WIDTH;
+
+	indir = len > 8 * REG_WIDTH;
+	/* Setup PREV_ALU for indirect mode. */
+	if (indir)
+		wrp_immed(nfp_prog, reg_none(),
+			  CMD_OVE_LEN | FIELD_PREP(CMD_OV_LEN, xfer_num - 1));
+
+	/* Cache memory into transfer-in registers. */
+	emit_cmd_any(nfp_prog, CMD_TGT_READ32_SWAP, CMD_MODE_32b, 0, src_base,
+		     off, xfer_num - 1, true, indir);
+}
+
+static int
+mem_ldx_data_from_pktcache_aligned(struct nfp_prog *nfp_prog,
+				   struct nfp_insn_meta *meta,
+				   unsigned int size)
+{
+	swreg dst_lo, dst_hi, src_lo;
+	u8 dst_gpr, idx;
+
+	idx = (meta->insn.off - meta->pkt_cache.range_start) / REG_WIDTH;
+	dst_gpr = meta->insn.dst_reg * 2;
+	dst_hi = reg_both(dst_gpr + 1);
+	dst_lo = reg_both(dst_gpr);
+	src_lo = reg_xfer(idx);
+
+	if (size < REG_WIDTH) {
+		wrp_reg_subpart(nfp_prog, dst_lo, src_lo, size, 0);
+		wrp_immed(nfp_prog, dst_hi, 0);
+	} else if (size == REG_WIDTH) {
+		wrp_mov(nfp_prog, dst_lo, src_lo);
+		wrp_immed(nfp_prog, dst_hi, 0);
+	} else {
+		swreg src_hi = reg_xfer(idx + 1);
+
+		wrp_mov(nfp_prog, dst_lo, src_lo);
+		wrp_mov(nfp_prog, dst_hi, src_hi);
+	}
+
+	return 0;
+}
+
+static int
+mem_ldx_data_from_pktcache(struct nfp_prog *nfp_prog,
+			   struct nfp_insn_meta *meta, unsigned int size)
+{
+	u8 off = meta->insn.off - meta->pkt_cache.range_start;
+
+	if (WARN_ON_ONCE(!IS_ALIGNED(off, REG_WIDTH)))
+		return -EOPNOTSUPP;
+
+	return mem_ldx_data_from_pktcache_aligned(nfp_prog, meta, size);
+}
+
 static int
 mem_ldx(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 	unsigned int size)
@@ -1852,8 +1920,16 @@ mem_ldx(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 			return mem_ldx_skb(nfp_prog, meta, size);
 	}
 
-	if (meta->ptr.type == PTR_TO_PACKET)
-		return mem_ldx_data(nfp_prog, meta, size);
+	if (meta->ptr.type == PTR_TO_PACKET) {
+		if (meta->pkt_cache.range_end) {
+			if (meta->pkt_cache.do_init)
+				mem_ldx_data_init_pktcache(nfp_prog, meta);
+
+			return mem_ldx_data_from_pktcache(nfp_prog, meta, size);
+		} else {
+			return mem_ldx_data(nfp_prog, meta, size);
+		}
+	}
 
 	if (meta->ptr.type == PTR_TO_STACK)
 		return mem_ldx_stack(nfp_prog, meta, size,

drivers/net/ethernet/netronome/nfp/bpf/main.h

@@ -199,6 +199,10 @@ typedef int (*instr_cb_t)(struct nfp_prog *, struct nfp_insn_meta *);
  * @ldst_gather_len: memcpy length gathered from load/store sequence
  * @paired_st: the paired store insn at the head of the sequence
  * @ptr_not_const: pointer is not always constant
+ * @pkt_cache: packet data cache information
+ * @pkt_cache.range_start: start offset for associated packet data cache
+ * @pkt_cache.range_end: end offset for associated packet data cache
+ * @pkt_cache.do_init: this read needs to initialize packet data cache
  * @jmp_dst: destination info for jump instructions
  * @func_id: function id for call instructions
  * @arg1: arg1 for call instructions
@@ -219,6 +223,11 @@ struct nfp_insn_meta {
 			struct bpf_insn *paired_st;
 			s16 ldst_gather_len;
 			bool ptr_not_const;
+			struct {
+				s16 range_start;
+				s16 range_end;
+				bool do_init;
+			} pkt_cache;
 		};
 		struct nfp_insn_meta *jmp_dst;
 		struct {

drivers/net/ethernet/netronome/nfp/nfp_asm.h

@@ -39,6 +39,7 @@
 #include <linux/types.h>
 
 #define REG_NONE	0
+#define REG_WIDTH	4
 
 #define RE_REG_NO_DST	0x020
 #define RE_REG_IMM	0x020