[Intel-wired-lan] [PATCH net-next v1] idpf: export RX hardware timestamping information to XDP

[Loktionov, Aleksandr]

> -----Original Message-----
> From: Mina Almasry <almasrymina at google.com>
> Sent: Monday, December 1, 2025 2:27 AM
> To: Loktionov, Aleksandr <aleksandr.loktionov at intel.com>
> Cc: netdev at vger.kernel.org; bpf at vger.kernel.org; linux-
> kernel at vger.kernel.org; YiFei Zhu <zhuyifei at google.com>; Alexei
> Starovoitov <ast at kernel.org>; Daniel Borkmann <daniel at iogearbox.net>;
> David S. Miller <davem at davemloft.net>; Jakub Kicinski
> <kuba at kernel.org>; Jesper Dangaard Brouer <hawk at kernel.org>; John
> Fastabend <john.fastabend at gmail.com>; Stanislav Fomichev
> <sdf at fomichev.me>; Nguyen, Anthony L <anthony.l.nguyen at intel.com>;
> Kitszel, Przemyslaw <przemyslaw.kitszel at intel.com>; Andrew Lunn
> <andrew+netdev at lunn.ch>; Eric Dumazet <edumazet at google.com>; Paolo
> Abeni <pabeni at redhat.com>; Lobakin, Aleksander
> <aleksander.lobakin at intel.com>; Richard Cochran
> <richardcochran at gmail.com>; intel-wired-lan at lists.osuosl.org
> Subject: Re: [Intel-wired-lan] [PATCH net-next v1] idpf: export RX
> hardware timestamping information to XDP
> 
> On Mon, Nov 24, 2025 at 2:33 AM Loktionov, Aleksandr
> <aleksandr.loktionov at intel.com> wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: Intel-wired-lan <intel-wired-lan-bounces at osuosl.org> On
> Behalf
> > > Of Mina Almasry
> > > Sent: Saturday, November 22, 2025 3:09 PM
> > > To: netdev at vger.kernel.org; bpf at vger.kernel.org; linux-
> > > kernel at vger.kernel.org
> > > Cc: YiFei Zhu <zhuyifei at google.com>; Alexei Starovoitov
> > > <ast at kernel.org>; Daniel Borkmann <daniel at iogearbox.net>; David S.
> > > Miller <davem at davemloft.net>; Jakub Kicinski <kuba at kernel.org>;
> > > Jesper Dangaard Brouer <hawk at kernel.org>; John Fastabend
> > > <john.fastabend at gmail.com>; Stanislav Fomichev <sdf at fomichev.me>;
> > > Nguyen, Anthony L <anthony.l.nguyen at intel.com>; Kitszel,
> Przemyslaw
> > > <przemyslaw.kitszel at intel.com>; Andrew Lunn
> <andrew+netdev at lunn.ch>;
> > > Eric Dumazet <edumazet at google.com>; Paolo Abeni
> <pabeni at redhat.com>;
> > > Lobakin, Aleksander <aleksander.lobakin at intel.com>; Richard
> Cochran
> > > <richardcochran at gmail.com>; intel-wired-lan at lists.osuosl.org; Mina
> > > Almasry <almasrymina at google.com>
> > > Subject: [Intel-wired-lan] [PATCH net-next v1] idpf: export RX
> > > hardware timestamping information to XDP
> > >
> > > From: YiFei Zhu <zhuyifei at google.com>
> > >
> > > The logic is similar to idpf_rx_hwtstamp, but the data is exported
> > > as a BPF kfunc instead of appended to an skb.
> > >
> > > A idpf_queue_has(PTP, rxq) condition is added to check the queue
> > > supports PTP similar to idpf_rx_process_skb_fields.
> > >
> > > Cc: intel-wired-lan at lists.osuosl.org
> > >
> > > Signed-off-by: YiFei Zhu <zhuyifei at google.com>
> > > Signed-off-by: Mina Almasry <almasrymina at google.com>
> > > ---
> > >  drivers/net/ethernet/intel/idpf/xdp.c | 27
> > > +++++++++++++++++++++++++++
> > >  1 file changed, 27 insertions(+)
> > >
> > > diff --git a/drivers/net/ethernet/intel/idpf/xdp.c
> > > b/drivers/net/ethernet/intel/idpf/xdp.c
> > > index 21ce25b0567f..850389ca66b6 100644
> > > --- a/drivers/net/ethernet/intel/idpf/xdp.c
> > > +++ b/drivers/net/ethernet/intel/idpf/xdp.c
> > > @@ -2,6 +2,7 @@
> > >  /* Copyright (C) 2025 Intel Corporation */
> > >
> > >  #include "idpf.h"
> > > +#include "idpf_ptp.h"
> > >  #include "idpf_virtchnl.h"
> > >  #include "xdp.h"
> > >  #include "xsk.h"
> > > @@ -369,6 +370,31 @@ int idpf_xdp_xmit(struct net_device *dev, int
> > > n, struct xdp_frame **frames,
> > >                                      idpf_xdp_tx_finalize);  }
> > >
> > > +static int idpf_xdpmo_rx_timestamp(const struct xdp_md *ctx, u64
> > > +*timestamp) {
> > > +     const struct virtchnl2_rx_flex_desc_adv_nic_3 *rx_desc;
> > > +     const struct libeth_xdp_buff *xdp = (typeof(xdp))ctx;
> > > +     const struct idpf_rx_queue *rxq;
> > > +     u64 cached_time, ts_ns;
> > > +     u32 ts_high;
> > > +
> > > +     rx_desc = xdp->desc;
> > > +     rxq = libeth_xdp_buff_to_rq(xdp, typeof(*rxq), xdp_rxq);
> > > +
> > > +     if (!idpf_queue_has(PTP, rxq))
> > > +             return -ENODATA;
> > > +     if (!(rx_desc->ts_low & VIRTCHNL2_RX_FLEX_TSTAMP_VALID))
> > > +             return -ENODATA;
> > RX flex desc fields are little‑endian.
> > You already convert ts_high with le32_to_cpu(), but test ts_low
> directly against the mask.
> > On big‑endian this can misdetect the bit and spuriously return -
> ENODATA.
> > Please convert ts_low to host order before the bit test.
> > See existing IDPF/ICE patterns where descriptor words are
> leXX_to_cpu()‑converted prior to FIELD_GET() / bit checks.
> > Also, per the XDP RX metadata kfunc docs, -ENODATA must reflect true
> absence of per‑packet metadata; endianness‑correct testing is required
> to uphold the semantic.
> >
> 
> Hey, sorry for the late reply. Initially when I read the reply, I
> thought: "why not, lets add a leXX_to_cpu".
> 
> But now that I look closer to implement the change and submit v2, it
> looks correct as written. ts_low is defined as a u8:
> 
> ```
> struct virtchnl2_rx_flex_desc_adv_nic_3 { ...
> u8 ts_low;
> ```
> 
> So it should not be fed into any leXX_to_cpu() functions, no?
> 
> I also looked at other u8 members in this struct like `u8
> status_err0_qw0` and `u8 status_err0_qw1`, and both are used in
> existing code without a conversion. So it seems correct as written.
> Can you reconsdirer?
> 
Oh, yes. You are right. For u8 byte endianness has no sense. Sorry.

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov at intel.com>