nfp: bpf: support setting the RX queue index

BPF has access to all internal FW datapath structures.  Including
the structure containing RX queue selection.  With little coordination
with the datapath we can let the offloaded BPF select the RX queue.
We just need a way to tell the datapath that queue selection has already
been done and it shouldn't overwrite it.  Define a bit to tell datapath
BPF already selected a queue (QSEL_SET), if the selected queue is not
enabled (>= number of enabled queues) datapath will perform normal RSS.

BPF queue selection on the NIC can be used to replace standard
datapath RSS with fully programmable BPF/XDP RSS.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 26 insertions, 2 deletions

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
index e163f3cfa47d..844a9be6e55a 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
@@ -468,6 +468,30 @@ nfp_bpf_check_ptr(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 }
 
 static int
+nfp_bpf_check_store(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
+		    struct bpf_verifier_env *env)
+{
+	const struct bpf_reg_state *reg = cur_regs(env) + meta->insn.dst_reg;
+
+	if (reg->type == PTR_TO_CTX) {
+		if (nfp_prog->type == BPF_PROG_TYPE_XDP) {
+			/* XDP ctx accesses must be 4B in size */
+			switch (meta->insn.off) {
+			case offsetof(struct xdp_md, rx_queue_index):
+				if (nfp_prog->bpf->queue_select)
+					goto exit_check_ptr;
+				pr_vlog(env, "queue selection not supported by FW\n");
+				return -EOPNOTSUPP;
+			}
+		}
+		pr_vlog(env, "unsupported store to context field\n");
+		return -EOPNOTSUPP;
+	}
+exit_check_ptr:
+	return nfp_bpf_check_ptr(nfp_prog, meta, env, meta->insn.dst_reg);
+}
+
+static int
 nfp_bpf_check_xadd(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 		   struct bpf_verifier_env *env)
 {
@@ -522,8 +546,8 @@ nfp_verify_insn(struct bpf_verifier_env *env, int insn_idx, int prev_insn_idx)
 		return nfp_bpf_check_ptr(nfp_prog, meta, env,
 					 meta->insn.src_reg);
 	if (is_mbpf_store(meta))
-		return nfp_bpf_check_ptr(nfp_prog, meta, env,
-					 meta->insn.dst_reg);
+		return nfp_bpf_check_store(nfp_prog, meta, env);
+
 	if (is_mbpf_xadd(meta))
 		return nfp_bpf_check_xadd(nfp_prog, meta, env);