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Message-ID: <1720424536.972943-1-xuanzhuo@linux.alibaba.com>
Date: Mon, 8 Jul 2024 15:42:16 +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 v7 09/10] virtio_net: xsk: rx: support recv small mode
On Mon, 8 Jul 2024 15:00:50 +0800, Jason Wang <jasowang@...hat.com> wrote:
> On Fri, Jul 5, 2024 at 3:38 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> >
> > In the process:
> > 1. We may need to copy data to create skb for XDP_PASS.
> > 2. We may need to call xsk_buff_free() to release the buffer.
> > 3. The handle for xdp_buff is difference from the buffer.
> >
> > If we pushed this logic into existing receive handle(merge and small),
> > we would have to maintain code scattered inside merge and small (and big).
> > So I think it is a good choice for us to put the xsk code into an
> > independent function.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > ---
> >
> > v7:
> > 1. rename xdp_construct_skb to xsk_construct_skb
> > 2. refactor virtnet_receive()
> >
> > drivers/net/virtio_net.c | 176 +++++++++++++++++++++++++++++++++++++--
> > 1 file changed, 168 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 2b27f5ada64a..64d8cd481890 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -498,6 +498,12 @@ struct virtio_net_common_hdr {
> > };
> >
> > static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf);
> > +static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
> > + struct net_device *dev,
> > + unsigned int *xdp_xmit,
> > + struct virtnet_rq_stats *stats);
> > +static void virtnet_receive_done(struct virtnet_info *vi, struct receive_queue *rq,
> > + struct sk_buff *skb, u8 flags);
> >
> > static bool is_xdp_frame(void *ptr)
> > {
> > @@ -1062,6 +1068,124 @@ static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
> > sg->length = len;
> > }
> >
> > +static struct xdp_buff *buf_to_xdp(struct virtnet_info *vi,
> > + struct receive_queue *rq, void *buf, u32 len)
> > +{
> > + struct xdp_buff *xdp;
> > + u32 bufsize;
> > +
> > + xdp = (struct xdp_buff *)buf;
> > +
> > + bufsize = xsk_pool_get_rx_frame_size(rq->xsk_pool) + vi->hdr_len;
> > +
> > + if (unlikely(len > bufsize)) {
> > + pr_debug("%s: rx error: len %u exceeds truesize %u\n",
> > + vi->dev->name, len, bufsize);
> > + DEV_STATS_INC(vi->dev, rx_length_errors);
> > + xsk_buff_free(xdp);
> > + return NULL;
> > + }
> > +
> > + xsk_buff_set_size(xdp, len);
> > + xsk_buff_dma_sync_for_cpu(xdp);
> > +
> > + return xdp;
> > +}
> > +
> > +static struct sk_buff *xsk_construct_skb(struct receive_queue *rq,
> > + struct xdp_buff *xdp)
> > +{
> > + unsigned int metasize = xdp->data - xdp->data_meta;
> > + struct sk_buff *skb;
> > + unsigned int size;
> > +
> > + size = xdp->data_end - xdp->data_hard_start;
> > + skb = napi_alloc_skb(&rq->napi, size);
> > + if (unlikely(!skb)) {
> > + xsk_buff_free(xdp);
> > + return NULL;
> > + }
> > +
> > + skb_reserve(skb, xdp->data_meta - xdp->data_hard_start);
> > +
> > + size = xdp->data_end - xdp->data_meta;
> > + memcpy(__skb_put(skb, size), xdp->data_meta, size);
> > +
> > + if (metasize) {
> > + __skb_pull(skb, metasize);
> > + skb_metadata_set(skb, metasize);
> > + }
> > +
> > + xsk_buff_free(xdp);
> > +
> > + return skb;
> > +}
> > +
> > +static struct sk_buff *virtnet_receive_xsk_small(struct net_device *dev, struct virtnet_info *vi,
> > + struct receive_queue *rq, struct xdp_buff *xdp,
> > + unsigned int *xdp_xmit,
> > + struct virtnet_rq_stats *stats)
> > +{
> > + struct bpf_prog *prog;
> > + u32 ret;
> > +
> > + ret = XDP_PASS;
> > + rcu_read_lock();
> > + prog = rcu_dereference(rq->xdp_prog);
> > + if (prog)
> > + ret = virtnet_xdp_handler(prog, xdp, dev, xdp_xmit, stats);
> > + rcu_read_unlock();
> > +
> > + switch (ret) {
> > + case XDP_PASS:
> > + return xsk_construct_skb(rq, xdp);
> > +
> > + case XDP_TX:
> > + case XDP_REDIRECT:
> > + return NULL;
> > +
> > + default:
> > + /* drop packet */
> > + xsk_buff_free(xdp);
> > + u64_stats_inc(&stats->drops);
> > + return NULL;
> > + }
> > +}
> > +
> > +static void virtnet_receive_xsk_buf(struct virtnet_info *vi, struct receive_queue *rq,
> > + void *buf, u32 len,
> > + unsigned int *xdp_xmit,
> > + struct virtnet_rq_stats *stats)
> > +{
> > + struct net_device *dev = vi->dev;
> > + struct sk_buff *skb = NULL;
> > + struct xdp_buff *xdp;
> > + u8 flags;
> > +
> > + len -= vi->hdr_len;
> > +
> > + u64_stats_add(&stats->bytes, len);
> > +
> > + xdp = buf_to_xdp(vi, rq, buf, len);
> > + if (!xdp)
> > + return;
> > +
> > + if (unlikely(len < ETH_HLEN)) {
> > + pr_debug("%s: short packet %i\n", dev->name, len);
> > + DEV_STATS_INC(dev, rx_length_errors);
> > + xsk_buff_free(xdp);
> > + return;
> > + }
> > +
> > + flags = ((struct virtio_net_common_hdr *)(xdp->data - vi->hdr_len))->hdr.flags;
> > +
> > + if (!vi->mergeable_rx_bufs)
> > + skb = virtnet_receive_xsk_small(dev, vi, rq, xdp, xdp_xmit, stats);
>
> I wonder if we add the mergeable support in the next patch would it be
> better to re-order the patch? For example, the xsk binding needs to be
> moved to the last patch, otherwise we break xsk with a mergeable
> buffer here?
If you worry that the user works with this commit, I want to say you do not
worry.
Because the flags NETDEV_XDP_ACT_XSK_ZEROCOPY is not added. I plan to add that
after the tx is completed.
I do test by adding this flags locally.
Thanks.
>
> Or anything I missed here?
>
> Thanks
>
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