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

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Date: Mon, 1 Jul 2024 11:05:33 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.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, Jun 28, 2024 at 1:44 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> 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 meant a patch to s/VIRTIO_XDP_HEADROOM/XDP_PACKET_HEADROOM/g.

>
> 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.

I mean do we need a check to fail xsk binding if vi->hdr_len >
xsk_pool_get_headroom() or it has been guaranteed by the code already.

Thanks

>
> Thanks.
>
>
> >
> > Thanks
> >
>