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, 47 insertions, 0 deletions

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/jit.c b/drivers/net/ethernet/netronome/nfp/bpf/jit.c
index 326a2085d650..a4d3da215863 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/jit.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/jit.c
@@ -42,6 +42,7 @@
 
 #include "main.h"
 #include "../nfp_asm.h"
+#include "../nfp_net_ctrl.h"
 
 /* --- NFP prog --- */
 /* Foreach "multiple" entries macros provide pos and next<n> pointers.
@@ -1470,6 +1471,38 @@ nfp_perf_event_output(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 	return 0;
 }
 
+static int
+nfp_queue_select(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	u32 jmp_tgt;
+
+	jmp_tgt = nfp_prog_current_offset(nfp_prog) + 5;
+
+	/* Make sure the queue id fits into FW field */
+	emit_alu(nfp_prog, reg_none(), reg_a(meta->insn.src_reg * 2),
+		 ALU_OP_AND_NOT_B, reg_imm(0xff));
+	emit_br(nfp_prog, BR_BEQ, jmp_tgt, 2);
+
+	/* Set the 'queue selected' bit and the queue value */
+	emit_shf(nfp_prog, pv_qsel_set(nfp_prog),
+		 pv_qsel_set(nfp_prog), SHF_OP_OR, reg_imm(1),
+		 SHF_SC_L_SHF, PKT_VEL_QSEL_SET_BIT);
+	emit_ld_field(nfp_prog,
+		      pv_qsel_val(nfp_prog), 0x1, reg_b(meta->insn.src_reg * 2),
+		      SHF_SC_NONE, 0);
+	/* Delay slots end here, we will jump over next instruction if queue
+	 * value fits into the field.
+	 */
+	emit_ld_field(nfp_prog,
+		      pv_qsel_val(nfp_prog), 0x1, reg_imm(NFP_NET_RXR_MAX),
+		      SHF_SC_NONE, 0);
+
+	if (!nfp_prog_confirm_current_offset(nfp_prog, jmp_tgt))
+		return -EINVAL;
+
+	return 0;
+}
+
 /* --- Callbacks --- */
 static int mov_reg64(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
@@ -2160,6 +2193,17 @@ mem_stx_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 			    false, wrp_lmem_store);
 }
 
+static int mem_stx_xdp(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	switch (meta->insn.off) {
+	case offsetof(struct xdp_md, rx_queue_index):
+		return nfp_queue_select(nfp_prog, meta);
+	}
+
+	WARN_ON_ONCE(1); /* verifier should have rejected bad accesses */
+	return -EOPNOTSUPP;
+}
+
 static int
 mem_stx(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 	unsigned int size)
@@ -2186,6 +2230,9 @@ static int mem_stx2(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 
 static int mem_stx4(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
+	if (meta->ptr.type == PTR_TO_CTX)
+		if (nfp_prog->type == BPF_PROG_TYPE_XDP)
+			return mem_stx_xdp(nfp_prog, meta);
 	return mem_stx(nfp_prog, meta, 4);
 }