Re: [PATCH net-next v1 15/19] virtio_net: xsk: rx: introduce add_recvbuf_xsk()

[Jason Wang <jasowang@redhat.com>]

On Mon, Oct 16, 2023 at 8:01 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>
> Implement the logic of filling vq with XSK buffer.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
>  drivers/net/virtio/main.c       | 13 +++++++
>  drivers/net/virtio/virtio_net.h |  5 +++
>  drivers/net/virtio/xsk.c        | 66 ++++++++++++++++++++++++++++++++-
>  drivers/net/virtio/xsk.h        |  2 +
>  4 files changed, 85 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio/main.c b/drivers/net/virtio/main.c
> index 58bb38f9b453..0e740447b142 100644
> --- a/drivers/net/virtio/main.c
> +++ b/drivers/net/virtio/main.c
> @@ -1787,9 +1787,20 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
>  static bool try_fill_recv(struct virtnet_info *vi, struct virtnet_rq *rq,
>                           gfp_t gfp)
>  {
> +       struct xsk_buff_pool *pool;
>         int err;
>         bool oom;
>
> +       rcu_read_lock();

A question here: should we sync with refill work during rx_pause?

> +       pool = rcu_dereference(rq->xsk.pool);
> +       if (pool) {
> +               err = virtnet_add_recvbuf_xsk(vi, rq, pool, gfp);
> +               oom = err == -ENOMEM;
> +               rcu_read_unlock();
> +               goto kick;
> +       }
> +       rcu_read_unlock();

And if we synchronize with that there's probably no need for the rcu
and we can merge the logic with the following ones?

Thanks


> +
>         do {
>                 if (vi->mergeable_rx_bufs)
>                         err = add_recvbuf_mergeable(vi, rq, gfp);
> @@ -1802,6 +1813,8 @@ static bool try_fill_recv(struct virtnet_info *vi, struct virtnet_rq *rq,
>                 if (err)
>                         break;
>         } while (rq->vq->num_free);
> +
> +kick:
>         if (virtqueue_kick_prepare(rq->vq) && virtqueue_notify(rq->vq)) {
>                 unsigned long flags;
>
> diff --git a/drivers/net/virtio/virtio_net.h b/drivers/net/virtio/virtio_net.h
> index d4e620a084f4..6e71622fca45 100644
> --- a/drivers/net/virtio/virtio_net.h
> +++ b/drivers/net/virtio/virtio_net.h
> @@ -156,6 +156,11 @@ struct virtnet_rq {
>
>                 /* xdp rxq used by xsk */
>                 struct xdp_rxq_info xdp_rxq;
> +
> +               struct xdp_buff **xsk_buffs;
> +               u32 nxt_idx;
> +               u32 num;
> +               u32 size;
>         } xsk;
>  };
>
> diff --git a/drivers/net/virtio/xsk.c b/drivers/net/virtio/xsk.c
> index 973e783260c3..841fb078882a 100644
> --- a/drivers/net/virtio/xsk.c
> +++ b/drivers/net/virtio/xsk.c
> @@ -37,6 +37,58 @@ static void virtnet_xsk_check_queue(struct virtnet_sq *sq)
>                 netif_stop_subqueue(dev, qnum);
>  }
>
> +static int virtnet_add_recvbuf_batch(struct virtnet_info *vi, struct virtnet_rq *rq,
> +                                    struct xsk_buff_pool *pool, gfp_t gfp)
> +{
> +       struct xdp_buff **xsk_buffs;
> +       dma_addr_t addr;
> +       u32 len, i;
> +       int err = 0;
> +
> +       xsk_buffs = rq->xsk.xsk_buffs;
> +
> +       if (rq->xsk.nxt_idx >= rq->xsk.num) {
> +               rq->xsk.num = xsk_buff_alloc_batch(pool, xsk_buffs, rq->xsk.size);
> +               if (!rq->xsk.num)
> +                       return -ENOMEM;
> +               rq->xsk.nxt_idx = 0;
> +       }
> +
> +       while (rq->xsk.nxt_idx < rq->xsk.num) {
> +               i = rq->xsk.nxt_idx;
> +
> +               /* use the part of XDP_PACKET_HEADROOM as the virtnet hdr space */
> +               addr = xsk_buff_xdp_get_dma(xsk_buffs[i]) - vi->hdr_len;
> +               len = xsk_pool_get_rx_frame_size(pool) + vi->hdr_len;
> +
> +               sg_init_table(rq->sg, 1);
> +               sg_fill_dma(rq->sg, addr, len);
> +
> +               err = virtqueue_add_inbuf(rq->vq, rq->sg, 1, xsk_buffs[i], gfp);
> +               if (err)
> +                       return err;
> +
> +               rq->xsk.nxt_idx++;
> +       }
> +
> +       return 0;
> +}
> +
> +int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct virtnet_rq *rq,
> +                           struct xsk_buff_pool *pool, gfp_t gfp)
> +{
> +       int err;
> +
> +       do {
> +               err = virtnet_add_recvbuf_batch(vi, rq, pool, gfp);
> +               if (err)
> +                       return err;
> +
> +       } while (rq->vq->num_free);
> +
> +       return 0;
> +}
> +
>  static int virtnet_xsk_xmit_one(struct virtnet_sq *sq,
>                                 struct xsk_buff_pool *pool,
>                                 struct xdp_desc *desc)
> @@ -244,7 +296,7 @@ static int virtnet_xsk_pool_enable(struct net_device *dev,
>         struct virtnet_sq *sq;
>         struct device *dma_dev;
>         dma_addr_t hdr_dma;
> -       int err;
> +       int err, size;
>
>         /* In big_packets mode, xdp cannot work, so there is no need to
>          * initialize xsk of rq.
> @@ -276,6 +328,16 @@ static int virtnet_xsk_pool_enable(struct net_device *dev,
>         if (!dma_dev)
>                 return -EPERM;
>
> +       size = virtqueue_get_vring_size(rq->vq);
> +
> +       rq->xsk.xsk_buffs = kcalloc(size, sizeof(*rq->xsk.xsk_buffs), GFP_KERNEL);
> +       if (!rq->xsk.xsk_buffs)
> +               return -ENOMEM;
> +
> +       rq->xsk.size = size;
> +       rq->xsk.nxt_idx = 0;
> +       rq->xsk.num = 0;
> +
>         hdr_dma = dma_map_single(dma_dev, &xsk_hdr, vi->hdr_len, DMA_TO_DEVICE);
>         if (dma_mapping_error(dma_dev, hdr_dma))
>                 return -ENOMEM;
> @@ -338,6 +400,8 @@ static int virtnet_xsk_pool_disable(struct net_device *dev, u16 qid)
>         err1 = virtnet_sq_bind_xsk_pool(vi, sq, NULL);
>         err2 = virtnet_rq_bind_xsk_pool(vi, rq, NULL);
>
> +       kfree(rq->xsk.xsk_buffs);
> +
>         return err1 | err2;
>  }
>
> diff --git a/drivers/net/virtio/xsk.h b/drivers/net/virtio/xsk.h
> index 7ebc9bda7aee..bef41a3f954e 100644
> --- a/drivers/net/virtio/xsk.h
> +++ b/drivers/net/virtio/xsk.h
> @@ -23,4 +23,6 @@ int virtnet_xsk_pool_setup(struct net_device *dev, struct netdev_bpf *xdp);
>  bool virtnet_xsk_xmit(struct virtnet_sq *sq, struct xsk_buff_pool *pool,
>                       int budget);
>  int virtnet_xsk_wakeup(struct net_device *dev, u32 qid, u32 flag);
> +int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct virtnet_rq *rq,
> +                           struct xsk_buff_pool *pool, gfp_t gfp);
>  #endif
> --
> 2.32.0.3.g01195cf9f
>