linux-kernel - Re: [RFC net-next 5/9] ice: apply XDP offloading fixup when building skb

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Date: Fri, 21 Jun 2024 11:05:16 -0500
From: Yan Zhai <yan@...udflare.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
Cc: netdev@...r.kernel.org, Jesse Brandeburg <jesse.brandeburg@...el.com>, 
	Tony Nguyen <anthony.l.nguyen@...el.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Björn Töpel <bjorn@...nel.org>, 
	Magnus Karlsson <magnus.karlsson@...el.com>, 
	Maciej Fijalkowski <maciej.fijalkowski@...el.com>, Jonathan Lemon <jonathan.lemon@...il.com>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, 
	intel-wired-lan@...ts.osuosl.org, linux-kernel@...r.kernel.org, 
	bpf@...r.kernel.org
Subject: Re: [RFC net-next 5/9] ice: apply XDP offloading fixup when building skb

On Fri, Jun 21, 2024 at 4:22 AM Alexander Lobakin
<aleksander.lobakin@...el.com> wrote:
>
> From: Yan Zhai <yan@...udflare.com>
> Date: Thu, 20 Jun 2024 15:19:22 -0700
>
> > Add a common point to transfer offloading info from XDP context to skb.
> >
> > Signed-off-by: Yan Zhai <yan@...udflare.com>
> > Signed-off-by: Jesper Dangaard Brouer <hawk@...nel.org>
> > ---
> >  drivers/net/ethernet/intel/ice/ice_txrx.c | 2 ++
> >  drivers/net/ethernet/intel/ice/ice_xsk.c  | 6 +++++-
> >  include/net/xdp_sock_drv.h                | 2 +-
> >  3 files changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
> > index 8bb743f78fcb..a247306837ed 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_txrx.c
> > +++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
> > @@ -1222,6 +1222,7 @@ int ice_clean_rx_irq(struct ice_rx_ring *rx_ring, int budget)
> >
> >                       hard_start = page_address(rx_buf->page) + rx_buf->page_offset -
> >                                    offset;
> > +                     xdp_init_buff_minimal(xdp);
>
> Two lines below, you have this:
>
>         xdp_buff_clear_frags_flag(xdp);
>
> Which clears frags bit in xdp->flags. I.e. since you always clear flags
> here, this call becomes redundant.
> But I'd say that `xdp->flags = 0` really wants to be moved from
> xdp_init_buff() to xdp_prepare_buff().
>
You are right, there is some redundancy here. I will fix it if people
feel good about the use case in general :)


> >                       xdp_prepare_buff(xdp, hard_start, offset, size, !!offset);
> >  #if (PAGE_SIZE > 4096)
> >                       /* At larger PAGE_SIZE, frame_sz depend on len size */
> > @@ -1287,6 +1288,7 @@ int ice_clean_rx_irq(struct ice_rx_ring *rx_ring, int budget)
> >
> >               /* populate checksum, VLAN, and protocol */
> >               ice_process_skb_fields(rx_ring, rx_desc, skb);
> > +             xdp_buff_fixup_skb_offloading(xdp, skb);
> >
> >               ice_trace(clean_rx_irq_indicate, rx_ring, rx_desc, skb);
> >               /* send completed skb up the stack */
> > diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
> > index a65955eb23c0..367658acaab8 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_xsk.c
> > +++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
> > @@ -845,8 +845,10 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
> >       xdp_prog = READ_ONCE(rx_ring->xdp_prog);
> >       xdp_ring = rx_ring->xdp_ring;
> >
> > -     if (ntc != rx_ring->first_desc)
> > +     if (ntc != rx_ring->first_desc) {
> >               first = *ice_xdp_buf(rx_ring, rx_ring->first_desc);
> > +             xdp_init_buff_minimal(first);
>
> xdp_buff_set_size() always clears flags, this is redundant.
>
> > +     }
> >
> >       while (likely(total_rx_packets < (unsigned int)budget)) {
> >               union ice_32b_rx_flex_desc *rx_desc;
> > @@ -920,6 +922,7 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
> >                       break;
> >               }
> >
> > +             xdp = first;
> >               first = NULL;
> >               rx_ring->first_desc = ntc;
> >
> > @@ -934,6 +937,7 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
> >               vlan_tci = ice_get_vlan_tci(rx_desc);
> >
> >               ice_process_skb_fields(rx_ring, rx_desc, skb);
> > +             xdp_buff_fixup_skb_offloading(xdp, skb);
> >               ice_receive_skb(rx_ring, skb, vlan_tci);
> >       }
> >
> > diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
> > index 0a5dca2b2b3f..02243dc064c2 100644
> > --- a/include/net/xdp_sock_drv.h
> > +++ b/include/net/xdp_sock_drv.h
> > @@ -181,7 +181,7 @@ static inline void xsk_buff_set_size(struct xdp_buff *xdp, u32 size)
> >       xdp->data = xdp->data_hard_start + XDP_PACKET_HEADROOM;
> >       xdp->data_meta = xdp->data;
> >       xdp->data_end = xdp->data + size;
> > -     xdp->flags = 0;
> > +     xdp_init_buff_minimal(xdp);
>
> Why is this done in the patch prefixed with "ice:"?
>
Good catch, this should be moved to the previous patch.

thanks
Yan

> >  }
> >
> >  static inline dma_addr_t xsk_buff_raw_get_dma(struct xsk_buff_pool *pool,
>
> Thanks,
> Olek