Re: [PATCH RESEND bpf-next 02/15] ice: make RX HW timestamp reading code more reusable

Larysa Zaremba
2023-05-22T15:10:38Z

On Fri, May 19, 2023 at 06:52:13PM +0200, Alexander Lobakin wrote:
> From: Larysa Zaremba <larysa.zaremba@intel.com>
> Date: Fri, 12 May 2023 17:25:54 +0200
>
> > Previously, we only needed RX HW timestamp in skb path,
> > hence all related code was written with skb in mind.
> > But with the addition of XDP hints via kfuncs to the ice driver,
> > the same logic will be needed in .xmo_() callbacks.
>
> [...]
>
> > @@ -2176,9 +2174,8 @@ ice_ptp_rx_hwtstamp(struct ice_rx_ring *rx_ring,
> > ts_high = le32_to_cpu(rx_desc->wb.flex_ts.ts_high);
> > ts_ns = ice_ptp_extend_32b_ts(cached_time, ts_high);
> >
> > - hwtstamps = skb_hwtstamps(skb);
> > - memset(hwtstamps, 0, sizeof(*hwtstamps));
> > - hwtstamps->hwtstamp = ns_to_ktime(ts_ns);
> > + *dst = ts_ns;
> > + return true;
>
> Can't we use the same I wrote in the prev. comment, i.e. return 0 or
> timestamp? I don't think ts == 0 is valid.
>

Agreed with this in the answer to the previous email :)

> > }
> >
> > /**
>
> [...]
>
> > + * The driver receives a notification in the receive descriptor with timestamp.
> > + * The timestamp is in ns, so we must convert the result first.
> > + */
> > +static void
> > +ice_ptp_rx_hwts_to_skb(struct ice_rx_ring *rx_ring,
> > + union ice_32b_rx_flex_desc *rx_desc,
> > + struct sk_buff *skb)
> > +{
> > + struct skb_shared_hwtstamps *hwtstamps;
> > + u64 ts_ns;
> > +
> > + if (!ice_ptp_copy_rx_hwts_from_desc(rx_ring, rx_desc, &ts_ns))
> > + return;
> > +
> > + hwtstamps = skb_hwtstamps(skb);
> > + memset(hwtstamps, 0, sizeof(*hwtstamps));
> > + hwtstamps->hwtstamp = ns_to_ktime(ts_ns);
>
> Ok, my optimizations aren't in this series :D
> If you look at the hwtimestamps in skb, you'll see all that can be
> minimized to just:
>
> *skb_hwtstamps(skb) = (struct skb_shared_hwtstamps){
> .hwtstamp = ns_to_ktime(ts_ns),
> };
>
> Compiler will probably do its job, but I wouldn't always rely on it.
> Sometimes it's even able to not expand memset(8 bytes) to *(u64 *) = 0.

Ok, will fix.

>
> > +}
> > +
> > /**
> > * ice_process_skb_fields - Populate skb header fields from Rx descriptor
> > * @rx_ring: Rx descriptor ring packet is being transacted on
> > @@ -210,7 +235,7 @@ ice_process_skb_fields(struct ice_rx_ring *rx_ring,
> > ice_rx_csum(rx_ring, skb, rx_desc, ptype);
> >
> > if (rx_ring->ptp_rx)
> > - ice_ptp_rx_hwtstamp(rx_ring, rx_desc, skb);
> > + ice_ptp_rx_hwts_to_skb(rx_ring, rx_desc, skb);
> > }
> >
> > /**
>
> Thanks,
> Olek