nfp: bpf: add support for atomic add of unknown values

Allow atomic add to be used even when the value is not guaranteed
to fit into a 16 bit immediate.  This requires the value to be pulled
as data, and therefore use of a transfer register and a context swap.

Track the information about possible lengths of the value, if it's
guaranteed to be larger than 16bits don't generate the code for the
optimized case at all.

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>

1 files changed, 7 insertions, 7 deletions

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
index 40619efea77d..486ffd1d5913 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
@@ -414,16 +414,16 @@ nfp_bpf_check_xadd(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 			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);
+	if (sreg->type != SCALAR_VALUE) {
+		pr_vlog(env, "atomic add not of a scalar: %d\n", sreg->type);
 		return -EOPNOTSUPP;
 	}
 
+	meta->xadd_over_16bit |=
+		sreg->var_off.value > 0xffff || sreg->var_off.mask > 0xffff;
+	meta->xadd_maybe_16bit |=
+		(sreg->var_off.value & ~sreg->var_off.mask) <= 0xffff;
+
 	return nfp_bpf_check_ptr(nfp_prog, meta, env, meta->insn.dst_reg);
 }