Re: [PATCH net-next v3 10/15] virtio_net: introduce receive_small_xdp()

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On Tue, 25 Apr 2023 15:58:03 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
> On Sun, Apr 23, 2023 at 6:58 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
> >
> > The purpose of this patch is to simplify the receive_small().
> > Separate all the logic of XDP of small into a function.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> > ---
> >  drivers/net/virtio_net.c | 165 ++++++++++++++++++++++++---------------
> >  1 file changed, 100 insertions(+), 65 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index de5a579e8603..9b5fd2e0d27f 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -931,6 +931,99 @@ static struct page *xdp_linearize_page(struct receive_queue *rq,
> >         return NULL;
> >  }
> >
> > +static struct sk_buff *receive_small_xdp(struct net_device *dev,
> > +                                        struct virtnet_info *vi,
> > +                                        struct receive_queue *rq,
> > +                                        struct bpf_prog *xdp_prog,
> > +                                        void *buf,
> > +                                        unsigned int xdp_headroom,
> > +                                        unsigned int len,
> > +                                        unsigned int *xdp_xmit,
> > +                                        struct virtnet_rq_stats *stats)
> > +{
> > +       unsigned int header_offset = VIRTNET_RX_PAD + xdp_headroom;
> > +       unsigned int headroom = vi->hdr_len + header_offset;
> > +       struct virtio_net_hdr_mrg_rxbuf *hdr = buf + header_offset;
> > +       struct page *page = virt_to_head_page(buf);
> > +       struct page *xdp_page;
> > +       unsigned int buflen;
> > +       struct xdp_buff xdp;
> > +       struct sk_buff *skb;
> > +       unsigned int delta = 0;
> > +       unsigned int metasize = 0;
> > +       void *orig_data;
> > +       u32 act;
> > +
> > +       if (unlikely(hdr->hdr.gso_type))
> > +               goto err_xdp;
> > +
> > +       buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
> > +               SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> > +
> > +       if (unlikely(xdp_headroom < virtnet_get_headroom(vi))) {
> > +               int offset = buf - page_address(page) + header_offset;
> > +               unsigned int tlen = len + vi->hdr_len;
> > +               int num_buf = 1;
> > +
> > +               xdp_headroom = virtnet_get_headroom(vi);
> > +               header_offset = VIRTNET_RX_PAD + xdp_headroom;
> > +               headroom = vi->hdr_len + header_offset;
> > +               buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
> > +                       SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> > +               xdp_page = xdp_linearize_page(rq, &num_buf, page,
> > +                                             offset, header_offset,
> > +                                             &tlen);
> > +               if (!xdp_page)
> > +                       goto err_xdp;
> > +
> > +               buf = page_address(xdp_page);
> > +               put_page(page);
> > +               page = xdp_page;
> > +       }
> > +
> > +       xdp_init_buff(&xdp, buflen, &rq->xdp_rxq);
> > +       xdp_prepare_buff(&xdp, buf + VIRTNET_RX_PAD + vi->hdr_len,
> > +                        xdp_headroom, len, true);
> > +       orig_data = xdp.data;
> > +
> > +       act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> > +
> > +       switch (act) {
> > +       case XDP_PASS:
> > +               /* Recalculate length in case bpf program changed it */
> > +               delta = orig_data - xdp.data;
> > +               len = xdp.data_end - xdp.data;
> > +               metasize = xdp.data - xdp.data_meta;
> > +               break;
> > +
> > +       case XDP_TX:
> > +       case XDP_REDIRECT:
> > +               goto xdp_xmit;
> > +
> > +       default:
> > +               goto err_xdp;
> > +       }
> > +
> > +       skb = build_skb(buf, buflen);
> > +       if (!skb)
> > +               goto err;
> > +
> > +       skb_reserve(skb, headroom - delta);
> > +       skb_put(skb, len);
> > +       if (metasize)
> > +               skb_metadata_set(skb, metasize);
> > +
> > +       return skb;
> > +
> > +err_xdp:
> > +       stats->xdp_drops++;
> > +err:
> > +       stats->drops++;
> > +       put_page(page);
> > +xdp_xmit:
> > +       return NULL;
> > +}
>
> It looks like some of the comments of the above version is not addressed?
>
> "
> So we end up with some code duplication between receive_small() and
> receive_small_xdp() on building skbs. Is this intended?
> "

I answer you in the #13 commit of the above version. This patch-set has optimize
this with the last two commits. This commit is not unchanged.

Thanks.


>
> Thanks
>
> > +
> >  static struct sk_buff *receive_small(struct net_device *dev,
> >                                      struct virtnet_info *vi,
> >                                      struct receive_queue *rq,
> > @@ -947,9 +1040,6 @@ static struct sk_buff *receive_small(struct net_device *dev,
> >         unsigned int buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
> >                               SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> >         struct page *page = virt_to_head_page(buf);
> > -       unsigned int delta = 0;
> > -       struct page *xdp_page;
> > -       unsigned int metasize = 0;
> >
> >         len -= vi->hdr_len;
> >         stats->bytes += len;
> > @@ -969,56 +1059,10 @@ static struct sk_buff *receive_small(struct net_device *dev,
> >         rcu_read_lock();
> >         xdp_prog = rcu_dereference(rq->xdp_prog);
> >         if (xdp_prog) {
> > -               struct virtio_net_hdr_mrg_rxbuf *hdr = buf + header_offset;
> > -               struct xdp_buff xdp;
> > -               void *orig_data;
> > -               u32 act;
> > -
> > -               if (unlikely(hdr->hdr.gso_type))
> > -                       goto err_xdp;
> > -
> > -               if (unlikely(xdp_headroom < virtnet_get_headroom(vi))) {
> > -                       int offset = buf - page_address(page) + header_offset;
> > -                       unsigned int tlen = len + vi->hdr_len;
> > -                       int num_buf = 1;
> > -
> > -                       xdp_headroom = virtnet_get_headroom(vi);
> > -                       header_offset = VIRTNET_RX_PAD + xdp_headroom;
> > -                       headroom = vi->hdr_len + header_offset;
> > -                       buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
> > -                                SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> > -                       xdp_page = xdp_linearize_page(rq, &num_buf, page,
> > -                                                     offset, header_offset,
> > -                                                     &tlen);
> > -                       if (!xdp_page)
> > -                               goto err_xdp;
> > -
> > -                       buf = page_address(xdp_page);
> > -                       put_page(page);
> > -                       page = xdp_page;
> > -               }
> > -
> > -               xdp_init_buff(&xdp, buflen, &rq->xdp_rxq);
> > -               xdp_prepare_buff(&xdp, buf + VIRTNET_RX_PAD + vi->hdr_len,
> > -                                xdp_headroom, len, true);
> > -               orig_data = xdp.data;
> > -
> > -               act = virtnet_xdp_handler(xdp_prog, &xdp, dev, xdp_xmit, stats);
> > -
> > -               switch (act) {
> > -               case XDP_PASS:
> > -                       /* Recalculate length in case bpf program changed it */
> > -                       delta = orig_data - xdp.data;
> > -                       len = xdp.data_end - xdp.data;
> > -                       metasize = xdp.data - xdp.data_meta;
> > -                       break;
> > -               case XDP_TX:
> > -               case XDP_REDIRECT:
> > -                       rcu_read_unlock();
> > -                       goto xdp_xmit;
> > -               default:
> > -                       goto err_xdp;
> > -               }
> > +               skb = receive_small_xdp(dev, vi, rq, xdp_prog, buf, xdp_headroom,
> > +                                       len, xdp_xmit, stats);
> > +               rcu_read_unlock();
> > +               return skb;
> >         }
> >         rcu_read_unlock();
> >
> > @@ -1026,25 +1070,16 @@ static struct sk_buff *receive_small(struct net_device *dev,
> >         skb = build_skb(buf, buflen);
> >         if (!skb)
> >                 goto err;
> > -       skb_reserve(skb, headroom - delta);
> > +       skb_reserve(skb, headroom);
> >         skb_put(skb, len);
> > -       if (!xdp_prog) {
> > -               buf += header_offset;
> > -               memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
> > -       } /* keep zeroed vnet hdr since XDP is loaded */
> > -
> > -       if (metasize)
> > -               skb_metadata_set(skb, metasize);
> >
> > +       buf += header_offset;
> > +       memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
> >         return skb;
> >
> > -err_xdp:
> > -       rcu_read_unlock();
> > -       stats->xdp_drops++;
> >  err:
> >         stats->drops++;
> >         put_page(page);
> > -xdp_xmit:
> >         return NULL;
> >  }
> >
> > --
> > 2.32.0.3.g01195cf9f
> >
>




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