nfp: bpf: add basic support for atomic adds

Implement atomic add operation for 32 and 64 bit values.  Depend
on the verifier to ensure alignment.  Values have to be kept in
big endian and swapped upon read/write.  For now only support
atomic add of a constant.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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

@@ -2127,6 +2127,49 @@ static int mem_stx8(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 	return mem_stx(nfp_prog, meta, 8);
 }
 
+static int
+mem_xadd(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta, bool is64)
+{
+	swreg addra, addrb, off, prev_alu = imm_a(nfp_prog);
+	u8 dst_gpr = meta->insn.dst_reg * 2;
+	u8 src_gpr = meta->insn.src_reg * 2;
+
+	off = ur_load_imm_any(nfp_prog, meta->insn.off, imm_b(nfp_prog));
+
+	/* If insn has an offset add to the address */
+	if (!meta->insn.off) {
+		addra = reg_a(dst_gpr);
+		addrb = reg_b(dst_gpr + 1);
+	} else {
+		emit_alu(nfp_prog, imma_a(nfp_prog),
+			 reg_a(dst_gpr), ALU_OP_ADD, off);
+		emit_alu(nfp_prog, imma_b(nfp_prog),
+			 reg_a(dst_gpr + 1), ALU_OP_ADD_C, reg_imm(0));
+		addra = imma_a(nfp_prog);
+		addrb = imma_b(nfp_prog);
+	}
+
+	wrp_immed(nfp_prog, prev_alu,
+		  FIELD_PREP(CMD_OVE_DATA, 2) |
+		  CMD_OVE_LEN |
+		  FIELD_PREP(CMD_OV_LEN, 0x8 | is64 << 2));
+	wrp_reg_or_subpart(nfp_prog, prev_alu, reg_b(src_gpr), 2, 2);
+	emit_cmd_indir(nfp_prog, CMD_TGT_ADD_IMM, CMD_MODE_40b_BA, 0,
+		       addra, addrb, 0, false);
+
+	return 0;
+}
+
+static int mem_xadd4(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	return mem_xadd(nfp_prog, meta, false);
+}
+
+static int mem_xadd8(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	return mem_xadd(nfp_prog, meta, true);
+}
+
 static int jump(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
 	emit_br(nfp_prog, BR_UNC, meta->insn.off, 0);
@@ -2390,6 +2433,8 @@ static const instr_cb_t instr_cb[256] = {
 	[BPF_STX | BPF_MEM | BPF_H] =	mem_stx2,
 	[BPF_STX | BPF_MEM | BPF_W] =	mem_stx4,
 	[BPF_STX | BPF_MEM | BPF_DW] =	mem_stx8,
+	[BPF_STX | BPF_XADD | BPF_W] =	mem_xadd4,
+	[BPF_STX | BPF_XADD | BPF_DW] =	mem_xadd8,
 	[BPF_ST | BPF_MEM | BPF_B] =	mem_st1,
 	[BPF_ST | BPF_MEM | BPF_H] =	mem_st2,
 	[BPF_ST | BPF_MEM | BPF_W] =	mem_st4,

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

@@ -72,6 +72,7 @@ enum nfp_relo_type {
 #define BR_OFF_RELO		15000
 
 enum static_regs {
+	STATIC_REG_IMMA		= 20, /* Bank AB */
 	STATIC_REG_IMM		= 21, /* Bank AB */
 	STATIC_REG_STACK	= 22, /* Bank A */
 	STATIC_REG_PKT_LEN	= 22, /* Bank B */
@@ -91,6 +92,8 @@ enum pkt_vec {
 #define pptr_reg(np)	pv_ctm_ptr(np)
 #define imm_a(np)	reg_a(STATIC_REG_IMM)
 #define imm_b(np)	reg_b(STATIC_REG_IMM)
+#define imma_a(np)	reg_a(STATIC_REG_IMMA)
+#define imma_b(np)	reg_b(STATIC_REG_IMMA)
 #define imm_both(np)	reg_both(STATIC_REG_IMM)
 
 #define NFP_BPF_ABI_FLAGS	reg_imm(0)
@@ -169,18 +172,27 @@ struct nfp_app_bpf {
 	} helpers;
 };
 
+enum nfp_bpf_map_use {
+	NFP_MAP_UNUSED = 0,
+	NFP_MAP_USE_READ,
+	NFP_MAP_USE_WRITE,
+	NFP_MAP_USE_ATOMIC_CNT,
+};
+
 /**
  * struct nfp_bpf_map - private per-map data attached to BPF maps for offload
  * @offmap:	pointer to the offloaded BPF map
  * @bpf:	back pointer to bpf app private structure
  * @tid:	table id identifying map on datapath
  * @l:		link on the nfp_app_bpf->map_list list
+ * @use_map:	map of how the value is used (in 4B chunks)
  */
 struct nfp_bpf_map {
 	struct bpf_offloaded_map *offmap;
 	struct nfp_app_bpf *bpf;
 	u32 tid;
 	struct list_head l;
+	enum nfp_bpf_map_use use_map[];
 };
 
 struct nfp_prog;
@@ -320,6 +332,11 @@ static inline bool is_mbpf_classic_store_pkt(const struct nfp_insn_meta *meta)
 	return is_mbpf_classic_store(meta) && meta->ptr.type == PTR_TO_PACKET;
 }
 
+static inline bool is_mbpf_xadd(const struct nfp_insn_meta *meta)
+{
+	return (meta->insn.code & ~BPF_SIZE_MASK) == (BPF_STX | BPF_XADD);
+}
+
 /**
  * struct nfp_prog - nfp BPF program
  * @bpf: backpointer to the bpf app priv structure

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

@@ -164,6 +164,41 @@ static int nfp_bpf_destroy(struct nfp_net *nn, struct bpf_prog *prog)
 	return 0;
 }
 
+/* Atomic engine requires values to be in big endian, we need to byte swap
+ * the value words used with xadd.
+ */
+static void nfp_map_bpf_byte_swap(struct nfp_bpf_map *nfp_map, void *value)
+{
+	u32 *word = value;
+	unsigned int i;
+
+	for (i = 0; i < DIV_ROUND_UP(nfp_map->offmap->map.value_size, 4); i++)
+		if (nfp_map->use_map[i] == NFP_MAP_USE_ATOMIC_CNT)
+			word[i] = (__force u32)cpu_to_be32(word[i]);
+}
+
+static int
+nfp_bpf_map_lookup_entry(struct bpf_offloaded_map *offmap,
+			 void *key, void *value)
+{
+	int err;
+
+	err = nfp_bpf_ctrl_lookup_entry(offmap, key, value);
+	if (err)
+		return err;
+
+	nfp_map_bpf_byte_swap(offmap->dev_priv, value);
+	return 0;
+}
+
+static int
+nfp_bpf_map_update_entry(struct bpf_offloaded_map *offmap,
+			 void *key, void *value, u64 flags)
+{
+	nfp_map_bpf_byte_swap(offmap->dev_priv, value);
+	return nfp_bpf_ctrl_update_entry(offmap, key, value, flags);
+}
+
 static int
 nfp_bpf_map_get_next_key(struct bpf_offloaded_map *offmap,
 			 void *key, void *next_key)
@@ -183,8 +218,8 @@ nfp_bpf_map_delete_elem(struct bpf_offloaded_map *offmap, void *key)
 
 static const struct bpf_map_dev_ops nfp_bpf_map_ops = {
 	.map_get_next_key	= nfp_bpf_map_get_next_key,
-	.map_lookup_elem	= nfp_bpf_ctrl_lookup_entry,
-	.map_update_elem	= nfp_bpf_ctrl_update_entry,
+	.map_lookup_elem	= nfp_bpf_map_lookup_entry,
+	.map_update_elem	= nfp_bpf_map_update_entry,
 	.map_delete_elem	= nfp_bpf_map_delete_elem,
 };
 
@@ -192,6 +227,7 @@ static int
 nfp_bpf_map_alloc(struct nfp_app_bpf *bpf, struct bpf_offloaded_map *offmap)
 {
 	struct nfp_bpf_map *nfp_map;
+	unsigned int use_map_size;
 	long long int res;
 
 	if (!bpf->maps.types)
@@ -226,7 +262,10 @@ nfp_bpf_map_alloc(struct nfp_app_bpf *bpf, struct bpf_offloaded_map *offmap)
 		return -ENOMEM;
 	}
 
-	nfp_map = kzalloc(sizeof(*nfp_map), GFP_USER);
+	use_map_size = DIV_ROUND_UP(offmap->map.value_size, 4) *
+		       FIELD_SIZEOF(struct nfp_bpf_map, use_map[0]);
+
+	nfp_map = kzalloc(sizeof(*nfp_map) + use_map_size, GFP_USER);
 	if (!nfp_map)
 		return -ENOMEM;
 

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

@@ -285,6 +285,72 @@ nfp_bpf_check_stack_access(struct nfp_prog *nfp_prog,
 	return -EINVAL;
 }
 
+static const char *nfp_bpf_map_use_name(enum nfp_bpf_map_use use)
+{
+	static const char * const names[] = {
+		[NFP_MAP_UNUSED]	= "unused",
+		[NFP_MAP_USE_READ]	= "read",
+		[NFP_MAP_USE_WRITE]	= "write",
+		[NFP_MAP_USE_ATOMIC_CNT] = "atomic",
+	};
+
+	if (use >= ARRAY_SIZE(names) || !names[use])
+		return "unknown";
+	return names[use];
+}
+
+static int
+nfp_bpf_map_mark_used_one(struct bpf_verifier_env *env,
+			  struct nfp_bpf_map *nfp_map,
+			  unsigned int off, enum nfp_bpf_map_use use)
+{
+	if (nfp_map->use_map[off / 4] != NFP_MAP_UNUSED &&
+	    nfp_map->use_map[off / 4] != use) {
+		pr_vlog(env, "map value use type conflict %s vs %s off: %u\n",
+			nfp_bpf_map_use_name(nfp_map->use_map[off / 4]),
+			nfp_bpf_map_use_name(use), off);
+		return -EOPNOTSUPP;
+	}
+
+	nfp_map->use_map[off / 4] = use;
+
+	return 0;
+}
+
+static int
+nfp_bpf_map_mark_used(struct bpf_verifier_env *env, struct nfp_insn_meta *meta,
+		      const struct bpf_reg_state *reg,
+		      enum nfp_bpf_map_use use)
+{
+	struct bpf_offloaded_map *offmap;
+	struct nfp_bpf_map *nfp_map;
+	unsigned int size, off;
+	int i, err;
+
+	if (!tnum_is_const(reg->var_off)) {
+		pr_vlog(env, "map value offset is variable\n");
+		return -EOPNOTSUPP;
+	}
+
+	off = reg->var_off.value + meta->insn.off + reg->off;
+	size = BPF_LDST_BYTES(&meta->insn);
+	offmap = map_to_offmap(reg->map_ptr);
+	nfp_map = offmap->dev_priv;
+
+	if (off + size > offmap->map.value_size) {
+		pr_vlog(env, "map value access out-of-bounds\n");
+		return -EINVAL;
+	}
+
+	for (i = 0; i < size; i += 4 - (off + i) % 4) {
+		err = nfp_bpf_map_mark_used_one(env, nfp_map, off + i, use);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
 static int
 nfp_bpf_check_ptr(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 		  struct bpf_verifier_env *env, u8 reg_no)
@@ -307,10 +373,22 @@ nfp_bpf_check_ptr(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 	}
 
 	if (reg->type == PTR_TO_MAP_VALUE) {
+		if (is_mbpf_load(meta)) {
+			err = nfp_bpf_map_mark_used(env, meta, reg,
+						    NFP_MAP_USE_READ);
+			if (err)
+				return err;
+		}
 		if (is_mbpf_store(meta)) {
 			pr_vlog(env, "map writes not supported\n");
 			return -EOPNOTSUPP;
 		}
+		if (is_mbpf_xadd(meta)) {
+			err = nfp_bpf_map_mark_used(env, meta, reg,
+						    NFP_MAP_USE_ATOMIC_CNT);
+			if (err)
+				return err;
+		}
 	}
 
 	if (meta->ptr.type != NOT_INIT && meta->ptr.type != reg->type) {
@@ -324,6 +402,31 @@ nfp_bpf_check_ptr(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 	return 0;
 }
 
+static int
+nfp_bpf_check_xadd(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
+		   struct bpf_verifier_env *env)
+{
+	const struct bpf_reg_state *sreg = cur_regs(env) + meta->insn.src_reg;
+	const struct bpf_reg_state *dreg = cur_regs(env) + meta->insn.dst_reg;
+
+	if (dreg->type != PTR_TO_MAP_VALUE) {
+		pr_vlog(env, "atomic add not to a map value pointer: %d\n",
+			dreg->type);
+		return -EOPNOTSUPP;
+	}
+	if (sreg->type != SCALAR_VALUE ||
+	    sreg->var_off.value > 0xffff || sreg->var_off.mask > 0xffff) {
+		char tn_buf[48];
+
+		tnum_strn(tn_buf, sizeof(tn_buf), sreg->var_off);
+		pr_vlog(env, "atomic add not of a small constant scalar: %s\n",
+			tn_buf);
+		return -EOPNOTSUPP;
+	}
+
+	return nfp_bpf_check_ptr(nfp_prog, meta, env, meta->insn.dst_reg);
+}
+
 static int
 nfp_verify_insn(struct bpf_verifier_env *env, int insn_idx, int prev_insn_idx)
 {
@@ -356,6 +459,8 @@ nfp_verify_insn(struct bpf_verifier_env *env, int insn_idx, int prev_insn_idx)
 	if (is_mbpf_store(meta))
 		return nfp_bpf_check_ptr(nfp_prog, meta, env,
 					 meta->insn.dst_reg);
+	if (is_mbpf_xadd(meta))
+		return nfp_bpf_check_xadd(nfp_prog, meta, env);
 
 	return 0;
 }

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

@@ -48,6 +48,7 @@ const struct cmd_tgt_act cmd_tgt_act[__CMD_TGT_MAP_SIZE] = {
 	[CMD_TGT_READ32_SWAP] =		{ 0x02, 0x5c },
 	[CMD_TGT_READ_LE] =		{ 0x01, 0x40 },
 	[CMD_TGT_READ_SWAP_LE] =	{ 0x03, 0x40 },
+	[CMD_TGT_ADD_IMM] =		{ 0x02, 0x47 },
 };
 
 static bool unreg_is_imm(u16 reg)

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

@@ -238,6 +238,7 @@ enum cmd_tgt_map {
 	CMD_TGT_READ32_SWAP,
 	CMD_TGT_READ_LE,
 	CMD_TGT_READ_SWAP_LE,
+	CMD_TGT_ADD_IMM,
 	__CMD_TGT_MAP_SIZE,
 };
 
@@ -254,6 +255,7 @@ enum cmd_ctx_swap {
 	CMD_CTX_NO_SWAP = 3,
 };
 
+#define CMD_OVE_DATA	GENMASK(5, 3)
 #define CMD_OVE_LEN	BIT(7)
 #define CMD_OV_LEN	GENMASK(12, 8)