Re: [PATCH net-next v5 07/15] virtio_net: refactor the xmit type

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Mon, 17 Jun 2024 13:00:11 +0800, Jason Wang <jasowang@redhat.com> wrote:
> On Fri, Jun 14, 2024 at 2:40 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> >
> > Because the af-xdp and sq premapped mode will introduce two
> > new xmit type, so I refactor the xmit type mechanism first.
> >
> > We use the last two bits of the pointer to distinguish the xmit type,
> > so we can distinguish four xmit types. Now we have two xmit types:
> > SKB and XDP.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > ---
> >  drivers/net/virtio_net.c | 58 +++++++++++++++++++++++++++-------------
> >  1 file changed, 40 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 161694957065..e84a4624549b 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -47,8 +47,6 @@ module_param(napi_tx, bool, 0644);
> >  #define VIRTIO_XDP_TX          BIT(0)
> >  #define VIRTIO_XDP_REDIR       BIT(1)
> >
> > -#define VIRTIO_XDP_FLAG        BIT(0)
> > -
> >  /* RX packet size EWMA. The average packet size is used to determine the packet
> >   * buffer size when refilling RX rings. As the entire RX ring may be refilled
> >   * at once, the weight is chosen so that the EWMA will be insensitive to short-
> > @@ -491,42 +489,62 @@ struct virtio_net_common_hdr {
> >
> >  static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf);
> >
> > -static bool is_xdp_frame(void *ptr)
> > +enum virtnet_xmit_type {
> > +       VIRTNET_XMIT_TYPE_SKB,
> > +       VIRTNET_XMIT_TYPE_XDP,
> > +};
> > +
> > +#define VIRTNET_XMIT_TYPE_MASK (VIRTNET_XMIT_TYPE_SKB | VIRTNET_XMIT_TYPE_XDP)
> > +
> > +static enum virtnet_xmit_type virtnet_xmit_ptr_strip(void **ptr)
> >  {
> > -       return (unsigned long)ptr & VIRTIO_XDP_FLAG;
> > +       unsigned long p = (unsigned long)*ptr;
> > +
> > +       *ptr = (void *)(p & ~VIRTNET_XMIT_TYPE_MASK);
> > +
> > +       return p & VIRTNET_XMIT_TYPE_MASK;
> >  }
> >
> > -static void *xdp_to_ptr(struct xdp_frame *ptr)
> > +static void *virtnet_xmit_ptr_mix(void *ptr, enum virtnet_xmit_type type)
>
> How about rename this to virtnet_ptr_to_token()?

Will fix.

>
> >  {
> > -       return (void *)((unsigned long)ptr | VIRTIO_XDP_FLAG);
> > +       return (void *)((unsigned long)ptr | type);
> >  }
> >
> > -static struct xdp_frame *ptr_to_xdp(void *ptr)
> > +static int virtnet_add_outbuf(struct send_queue *sq, int num, void *data,
> > +                             enum virtnet_xmit_type type)
> >  {
> > -       return (struct xdp_frame *)((unsigned long)ptr & ~VIRTIO_XDP_FLAG);
> > +       return virtqueue_add_outbuf(sq->vq, sq->sg, num,
> > +                                   virtnet_xmit_ptr_mix(data, type),
> > +                                   GFP_ATOMIC);
>
> Nit: I think we can just open-code this instead of using a helper.

Will fix.

Thanks.


>
> Others look good.
>
> Thanks
>
>
> >  }
> >
> >  static void __free_old_xmit(struct send_queue *sq, bool in_napi,
> >                             struct virtnet_sq_free_stats *stats)
> >  {
> > +       struct xdp_frame *frame;
> > +       struct sk_buff *skb;
> >         unsigned int len;
> >         void *ptr;
> >
> >         while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) {
> >                 ++stats->packets;
> >
> > -               if (!is_xdp_frame(ptr)) {
> > -                       struct sk_buff *skb = ptr;
> > +               switch (virtnet_xmit_ptr_strip(&ptr)) {
> > +               case VIRTNET_XMIT_TYPE_SKB:
> > +                       skb = ptr;
> >
> >                         pr_debug("Sent skb %p\n", skb);
> >
> >                         stats->bytes += skb->len;
> >                         napi_consume_skb(skb, in_napi);
> > -               } else {
> > -                       struct xdp_frame *frame = ptr_to_xdp(ptr);
> > +                       break;
> > +
> > +               case VIRTNET_XMIT_TYPE_XDP:
> > +                       frame = ptr;
> >
> >                         stats->bytes += xdp_get_frame_len(frame);
> >                         xdp_return_frame(frame);
> > +                       break;
> >                 }
> >         }
> >  }
> > @@ -1064,8 +1082,7 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
> >                             skb_frag_size(frag), skb_frag_off(frag));
> >         }
> >
> > -       err = virtqueue_add_outbuf(sq->vq, sq->sg, nr_frags + 1,
> > -                                  xdp_to_ptr(xdpf), GFP_ATOMIC);
> > +       err = virtnet_add_outbuf(sq, nr_frags + 1, xdpf, VIRTNET_XMIT_TYPE_XDP);
> >         if (unlikely(err))
> >                 return -ENOSPC; /* Caller handle free/refcnt */
> >
> > @@ -2557,7 +2574,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
> >                         return num_sg;
> >                 num_sg++;
> >         }
> > -       return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, GFP_ATOMIC);
> > +       return virtnet_add_outbuf(sq, num_sg, skb, VIRTNET_XMIT_TYPE_SKB);
> >  }
> >
> >  static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
> > @@ -5263,10 +5280,15 @@ static void free_receive_page_frags(struct virtnet_info *vi)
> >
> >  static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf)
> >  {
> > -       if (!is_xdp_frame(buf))
> > +       switch (virtnet_xmit_ptr_strip(&buf)) {
> > +       case VIRTNET_XMIT_TYPE_SKB:
> >                 dev_kfree_skb(buf);
> > -       else
> > -               xdp_return_frame(ptr_to_xdp(buf));
> > +               break;
> > +
> > +       case VIRTNET_XMIT_TYPE_XDP:
> > +               xdp_return_frame(buf);
> > +               break;
> > +       }
> >  }
> >
> >  static void free_unused_bufs(struct virtnet_info *vi)
> > --
> > 2.32.0.3.g01195cf9f
> >
>