netdev - Re: [PATCH net-next v6 07/10] virtio_net: xsk: rx: support fill with xsk buffer

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Date: Fri, 28 Jun 2024 13:42:36 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: Jason Wang <jasowang@...hat.com>
Cc: netdev@...r.kernel.org,
 "Michael S. Tsirkin" <mst@...hat.com>,
 Eugenio Pérez <eperezma@...hat.com>,
 "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>,
 Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>,
 virtualization@...ts.linux.dev,
 bpf@...r.kernel.org
Subject: Re: [PATCH net-next v6 07/10] virtio_net: xsk: rx: support fill with xsk buffer

On Fri, 28 Jun 2024 10:19:37 +0800, Jason Wang <jasowang@...hat.com> wrote:
> On Tue, Jun 18, 2024 at 3:57 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> >
> > Implement the logic of filling rq with XSK buffers.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > ---
> >  drivers/net/virtio_net.c | 68 ++++++++++++++++++++++++++++++++++++++--
> >  1 file changed, 66 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 2bbc715f22c6..2ac5668a94ce 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -355,6 +355,8 @@ struct receive_queue {
> >
> >                 /* xdp rxq used by xsk */
> >                 struct xdp_rxq_info xdp_rxq;
> > +
> > +               struct xdp_buff **xsk_buffs;
> >         } xsk;
> >  };
> >
> > @@ -1032,6 +1034,53 @@ static void check_sq_full_and_disable(struct virtnet_info *vi,
> >         }
> >  }
> >
> > +static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
> > +{
> > +       sg->dma_address = addr;
> > +       sg->length = len;
> > +}
> > +
> > +static int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct receive_queue *rq,
> > +                                  struct xsk_buff_pool *pool, gfp_t gfp)
> > +{
> > +       struct xdp_buff **xsk_buffs;
> > +       dma_addr_t addr;
> > +       u32 len, i;
> > +       int err = 0;
> > +       int num;
> > +
> > +       xsk_buffs = rq->xsk.xsk_buffs;
> > +
> > +       num = xsk_buff_alloc_batch(pool, xsk_buffs, rq->vq->num_free);
> > +       if (!num)
> > +               return -ENOMEM;
> > +
> > +       len = xsk_pool_get_rx_frame_size(pool) + vi->hdr_len;
> > +
> > +       for (i = 0; i < num; ++i) {
> > +               /* use the part of XDP_PACKET_HEADROOM as the virtnet hdr space */
> > +               addr = xsk_buff_xdp_get_dma(xsk_buffs[i]) - vi->hdr_len;
>
> We had VIRTIO_XDP_HEADROOM, can we reuse it? Or if it's redundant
> let's send a patch to switch to XDP_PACKET_HEADROOM.

Do you mean replace it inside the comment?

I want to describe use the headroom of xsk, the size of the headroom is
XDP_PACKET_HEADROOM.

>
> Btw, the code assumes vi->hdr_len < xsk_pool_get_headroom(). It's
> better to fail if it's not true when enabling xsk.

It is ok.

Thanks.


>
> Thanks
>