On 02/07/2025 16.58, Jesper Dangaard Brouer wrote:
From: Lorenzo Bianconi<lorenzo@xxxxxxxxxx>
Introduce the following kfuncs to store hw metadata provided by the NIC
into the xdp_buff struct:
- rx-hash: bpf_xdp_store_rx_hash
- rx-vlan: bpf_xdp_store_rx_vlan
- rx-hw-ts: bpf_xdp_store_rx_ts
Signed-off-by: Lorenzo Bianconi<lorenzo@xxxxxxxxxx>
Signed-off-by: Jesper Dangaard Brouer<hawk@xxxxxxxxxx>
---
include/net/xdp.h | 5 +++++
net/core/xdp.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 50 insertions(+)
diff --git a/net/core/xdp.c b/net/core/xdp.c
index bd3110fc7ef8..1ffba57714ea 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -963,12 +963,57 @@ __bpf_kfunc int bpf_xdp_metadata_rx_vlan_tag(const struct xdp_md *ctx,
[...]
+__bpf_kfunc int bpf_xdp_store_rx_ts(struct xdp_md *ctx, u64 ts)
+{
+ struct xdp_buff *xdp = (struct xdp_buff *)ctx;
+ struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
+ struct skb_shared_hwtstamps *shwt = &sinfo->hwtstamps;
+
+ shwt->hwtstamp = ts;
Here we are storing into the SKB shared_info struct. This is located at
the SKB data tail. Thus, this will very likely cause a cache-miss.
What about storing it into xdp->rx_meta and then starting a prefetch for
shared_info? (and updating patch-4 that moved it into SKB)
(Reviewers should be aware that writing into the xdp_frame headroom
(xdp->rx_meta) likely isn't a cache-miss, because all drivers does a
prefetchw for this memory prior to running BPF-prog).
+ xdp->flags |= XDP_FLAGS_META_RX_TS;
+
+ return 0;
+}
