[xdp-hints] Re: [PATCH bpf-next V3 5/6] igc: add XDP hints kfuncs for RX timestamp

["Song, Yoong Siang" <yoong.siang.song@intel.com>]

On Thursday, March 23, 2023 12:02 AM , Jesper Dangaard Brouer <brouer@redhat.com> wrote:
>The NIC hardware RX timestamping mechanism adds an optional tailored header
>before the MAC header containing packet reception time. Optional depending on
>RX descriptor TSIP status bit (IGC_RXDADV_STAT_TSIP). In case this bit is set
>driver does offset adjustments to packet data start and extracts the timestamp.
>
>The timestamp need to be extracted before invoking the XDP bpf_prog, because
>this area just before the packet is also accessible by XDP via data_meta context
>pointer (and helper bpf_xdp_adjust_meta). Thus, an XDP bpf_prog can potentially
>overwrite this and corrupt data that we want to extract with the new kfunc for
>reading the timestamp.
>
>Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
>---
> drivers/net/ethernet/intel/igc/igc.h      |    1 +
> drivers/net/ethernet/intel/igc/igc_main.c |   20 ++++++++++++++++++++
> 2 files changed, 21 insertions(+)
>
>diff --git a/drivers/net/ethernet/intel/igc/igc.h
>b/drivers/net/ethernet/intel/igc/igc.h
>index bc67a52e47e8..29941734f1a1 100644
>--- a/drivers/net/ethernet/intel/igc/igc.h
>+++ b/drivers/net/ethernet/intel/igc/igc.h
>@@ -503,6 +503,7 @@ struct igc_rx_buffer {  struct igc_xdp_buff {
> 	struct xdp_buff xdp;
> 	union igc_adv_rx_desc *rx_desc;
>+	ktime_t rx_ts; /* data indication bit IGC_RXDADV_STAT_TSIP */
> };
>
> struct igc_q_vector {
>diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
>b/drivers/net/ethernet/intel/igc/igc_main.c
>index a78d7e6bcfd6..f66285c85444 100644
>--- a/drivers/net/ethernet/intel/igc/igc_main.c
>+++ b/drivers/net/ethernet/intel/igc/igc_main.c
>@@ -2539,6 +2539,7 @@ static int igc_clean_rx_irq(struct igc_q_vector
>*q_vector, const int budget)
> 		if (igc_test_staterr(rx_desc, IGC_RXDADV_STAT_TSIP)) {
> 			timestamp = igc_ptp_rx_pktstamp(q_vector->adapter,
> 							pktbuf);
>+			ctx.rx_ts = timestamp;
> 			pkt_offset = IGC_TS_HDR_LEN;
> 			size -= IGC_TS_HDR_LEN;
> 		}
>@@ -2727,6 +2728,7 @@ static int igc_clean_rx_irq_zc(struct igc_q_vector
>*q_vector, const int budget)
> 		if (igc_test_staterr(desc, IGC_RXDADV_STAT_TSIP)) {
> 			timestamp = igc_ptp_rx_pktstamp(q_vector->adapter,
> 							bi->xdp->data);
>+			ctx->rx_ts = timestamp;
>
> 			bi->xdp->data += IGC_TS_HDR_LEN;
>
>@@ -6481,6 +6483,23 @@ u32 igc_rd32(struct igc_hw *hw, u32 reg)
> 	return value;
> }
>
>+static int igc_xdp_rx_timestamp(const struct xdp_md *_ctx, u64
>+*timestamp) {
>+	const struct igc_xdp_buff *ctx = (void *)_ctx;
>+
>+	if (igc_test_staterr(ctx->rx_desc, IGC_RXDADV_STAT_TSIP)) {
>+		*timestamp = ctx->rx_ts;
>+
>+		return 0;
>+	}
>+
>+	return -ENODATA;
>+}
>+
>+const struct xdp_metadata_ops igc_xdp_metadata_ops = {

Hi Jesper,

Since igc_xdp_metadata_ops is used on igc_main.c only, we can make
it static to avoid following build warning:

drivers/net/ethernet/intel/igc/igc_main.c:6499:31: warning: symbol
'igc_xdp_metadata_ops' was not declared. Should it be static?

Thanks & Regards
Siang

>+	.xmo_rx_timestamp		= igc_xdp_rx_timestamp,
>+};
>+
> /**
>  * igc_probe - Device Initialization Routine
>  * @pdev: PCI device information struct @@ -6554,6 +6573,7 @@ static int
>igc_probe(struct pci_dev *pdev,
> 	hw->hw_addr = adapter->io_addr;
>
> 	netdev->netdev_ops = &igc_netdev_ops;
>+	netdev->xdp_metadata_ops = &igc_xdp_metadata_ops;
> 	igc_ethtool_set_ops(netdev);
> 	netdev->watchdog_timeo = 5 * HZ;
>
>