[xdp-hints] [PATCH bpf-next V2 3/6] selftests/bpf: xdp_hw_metadata RX hash return code info

[Jesper Dangaard Brouer <brouer@redhat.com>]

When driver developers add XDP-hints kfuncs for RX hash it is
practical to print the return code in bpf_printk trace pipe log.

Print hash value as a hex value, both AF_XDP userspace and bpf_prog,
as this makes it easier to spot poor quality hashes.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 .../testing/selftests/bpf/progs/xdp_hw_metadata.c  |    9 ++++++---
 tools/testing/selftests/bpf/xdp_hw_metadata.c      |    5 ++++-
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c b/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
index 40c17adbf483..ce07010e4d48 100644
--- a/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
+++ b/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
@@ -77,10 +77,13 @@ int rx(struct xdp_md *ctx)
 		meta->rx_timestamp = 0; /* Used by AF_XDP as not avail signal */
 	}
 
-	if (!bpf_xdp_metadata_rx_hash(ctx, &meta->rx_hash))
-		bpf_printk("populated rx_hash with %u", meta->rx_hash);
-	else
+	ret = bpf_xdp_metadata_rx_hash(ctx, &meta->rx_hash);
+	if (ret >= 0) {
+		bpf_printk("populated rx_hash with 0x%08X", meta->rx_hash);
+	} else {
+		bpf_printk("rx_hash not-avail errno:%d", ret);
 		meta->rx_hash = 0; /* Used by AF_XDP as not avail signal */
+	}
 
 	return bpf_redirect_map(&xsk, ctx->rx_queue_index, XDP_PASS);
 }
diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c
index 400bfe19abfe..f3ec07ccdc95 100644
--- a/tools/testing/selftests/bpf/xdp_hw_metadata.c
+++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
@@ -3,6 +3,9 @@
 /* Reference program for verifying XDP metadata on real HW. Functional test
  * only, doesn't test the performance.
  *
+ * BPF-prog bpf_printk info outout can be access via
+ * /sys/kernel/debug/tracing/trace_pipe
+ *
  * RX:
  * - UDP 9091 packets are diverted into AF_XDP
  * - Metadata verified:
@@ -156,7 +159,7 @@ static void verify_xdp_metadata(void *data, clockid_t clock_id)
 
 	meta = data - sizeof(*meta);
 
-	printf("rx_hash: %u\n", meta->rx_hash);
+	printf("rx_hash: 0x%08X\n", meta->rx_hash);
 	printf("rx_timestamp:  %llu (sec:%0.4f)\n", meta->rx_timestamp,
 	       (double)meta->rx_timestamp / NANOSEC_PER_SEC);
 	if (meta->rx_timestamp) {