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Message-ID: <CACGkMEuigM1k5kMc8qU3z2ZBvTGH6=oVRkOCAZ0apsoQF3yuaA@mail.gmail.com>
Date: Fri, 20 Oct 2023 14:52:08 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	"Michael S. Tsirkin" <mst@...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-foundation.org, bpf@...r.kernel.org
Subject: Re: [PATCH net-next v1 11/19] virtio_net: xsk: tx: support tx

On Mon, Oct 16, 2023 at 8:01 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> The driver's tx napi is very important for XSK. It is responsible for
> obtaining data from the XSK queue and sending it out.
>
> At the beginning, we need to trigger tx napi.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
>  drivers/net/virtio/main.c       |  18 +++++-
>  drivers/net/virtio/virtio_net.h |   3 +-
>  drivers/net/virtio/xsk.c        | 108 ++++++++++++++++++++++++++++++++
>  drivers/net/virtio/xsk.h        |  13 ++++
>  4 files changed, 140 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio/main.c b/drivers/net/virtio/main.c
> index b320770e5f4e..a08429bef61f 100644
> --- a/drivers/net/virtio/main.c
> +++ b/drivers/net/virtio/main.c
> @@ -2054,7 +2054,9 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
>         struct virtnet_sq *sq = container_of(napi, struct virtnet_sq, napi);
>         struct virtnet_info *vi = sq->vq->vdev->priv;
>         unsigned int index = vq2txq(sq->vq);
> +       struct xsk_buff_pool *pool;
>         struct netdev_queue *txq;
> +       int busy = 0;
>         int opaque;
>         bool done;
>
> @@ -2067,11 +2069,25 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
>         txq = netdev_get_tx_queue(vi->dev, index);
>         __netif_tx_lock(txq, raw_smp_processor_id());
>         virtqueue_disable_cb(sq->vq);
> -       free_old_xmit(sq, true);
> +
> +       rcu_read_lock();
> +       pool = rcu_dereference(sq->xsk.pool);
> +       if (pool) {
> +               busy |= virtnet_xsk_xmit(sq, pool, budget);
> +               rcu_read_unlock();
> +       } else {
> +               rcu_read_unlock();
> +               free_old_xmit(sq, true);
> +       }
>
>         if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
>                 netif_tx_wake_queue(txq);
>
> +       if (busy) {
> +               __netif_tx_unlock(txq);
> +               return budget;
> +       }
> +
>         opaque = virtqueue_enable_cb_prepare(sq->vq);
>
>         done = napi_complete_done(napi, 0);
> diff --git a/drivers/net/virtio/virtio_net.h b/drivers/net/virtio/virtio_net.h
> index 9e69b6c5921b..3bbb1f5baad5 100644
> --- a/drivers/net/virtio/virtio_net.h
> +++ b/drivers/net/virtio/virtio_net.h
> @@ -9,7 +9,8 @@
>  #include <net/xdp_sock_drv.h>
>
>  #define VIRTIO_XDP_FLAG        BIT(0)
> -#define VIRTIO_XMIT_DATA_MASK (VIRTIO_XDP_FLAG)
> +#define VIRTIO_XSK_FLAG        BIT(1)
> +#define VIRTIO_XMIT_DATA_MASK (VIRTIO_XDP_FLAG | VIRTIO_XSK_FLAG)
>
>  /* 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
> diff --git a/drivers/net/virtio/xsk.c b/drivers/net/virtio/xsk.c
> index dddd01962a3f..0e775a9d270f 100644
> --- a/drivers/net/virtio/xsk.c
> +++ b/drivers/net/virtio/xsk.c
> @@ -7,6 +7,114 @@
>
>  static struct virtio_net_hdr_mrg_rxbuf xsk_hdr;
>
> +static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
> +{
> +       sg->dma_address = addr;
> +       sg->length = len;
> +}
> +
> +static void virtnet_xsk_check_queue(struct virtnet_sq *sq)
> +{
> +       struct virtnet_info *vi = sq->vq->vdev->priv;
> +       struct net_device *dev = vi->dev;
> +       int qnum = sq - vi->sq;
> +
> +       /* If it is a raw buffer queue, it does not check whether the status
> +        * of the queue is stopped when sending. So there is no need to check
> +        * the situation of the raw buffer queue.
> +        */
> +       if (virtnet_is_xdp_raw_buffer_queue(vi, qnum))
> +               return;
> +
> +       /* If this sq is not the exclusive queue of the current cpu,
> +        * then it may be called by start_xmit, so check it running out
> +        * of space.
> +        *
> +        * Stop the queue to avoid getting packets that we are
> +        * then unable to transmit. Then wait the tx interrupt.
> +        */
> +       if (sq->vq->num_free < 2 + MAX_SKB_FRAGS)
> +               netif_stop_subqueue(dev, qnum);
> +}
> +
> +static int virtnet_xsk_xmit_one(struct virtnet_sq *sq,
> +                               struct xsk_buff_pool *pool,
> +                               struct xdp_desc *desc)
> +{
> +       struct virtnet_info *vi;
> +       dma_addr_t addr;
> +
> +       vi = sq->vq->vdev->priv;
> +
> +       addr = xsk_buff_raw_get_dma(pool, desc->addr);
> +       xsk_buff_raw_dma_sync_for_device(pool, addr, desc->len);
> +
> +       sg_init_table(sq->sg, 2);
> +
> +       sg_fill_dma(sq->sg, sq->xsk.hdr_dma_address, vi->hdr_len);
> +       sg_fill_dma(sq->sg + 1, addr, desc->len);
> +
> +       return virtqueue_add_outbuf(sq->vq, sq->sg, 2,
> +                                   virtnet_xsk_to_ptr(desc->len), GFP_ATOMIC);
> +}
> +
> +static int virtnet_xsk_xmit_batch(struct virtnet_sq *sq,
> +                                 struct xsk_buff_pool *pool,
> +                                 unsigned int budget,
> +                                 struct virtnet_sq_stats *stats)
> +{
> +       struct xdp_desc *descs = pool->tx_descs;
> +       u32 nb_pkts, max_pkts, i;
> +       bool kick = false;
> +       int err;
> +
> +       max_pkts = min_t(u32, budget, sq->vq->num_free / 2);

Need document why num_free / 2 is chosen here.

Others look fine.

Thanks


> +
> +       nb_pkts = xsk_tx_peek_release_desc_batch(pool, max_pkts);
> +       if (!nb_pkts)
> +               return 0;
> +
> +       for (i = 0; i < nb_pkts; i++) {
> +               err = virtnet_xsk_xmit_one(sq, pool, &descs[i]);
> +               if (unlikely(err))
> +                       break;
> +
> +               kick = true;
> +       }
> +
> +       if (kick && virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq))
> +               ++stats->kicks;
> +
> +       stats->xdp_tx += i;
> +
> +       return i;
> +}
> +
> +bool virtnet_xsk_xmit(struct virtnet_sq *sq, struct xsk_buff_pool *pool,
> +                     int budget)
> +{
> +       struct virtnet_sq_stats stats = {};
> +       int sent;
> +
> +       virtnet_free_old_xmit(sq, true, &stats);
> +
> +       sent = virtnet_xsk_xmit_batch(sq, pool, budget, &stats);
> +
> +       virtnet_xsk_check_queue(sq);
> +
> +       u64_stats_update_begin(&sq->stats.syncp);
> +       sq->stats.packets += stats.packets;
> +       sq->stats.bytes += stats.bytes;
> +       sq->stats.kicks += stats.kicks;
> +       sq->stats.xdp_tx += stats.xdp_tx;
> +       u64_stats_update_end(&sq->stats.syncp);
> +
> +       if (xsk_uses_need_wakeup(pool))
> +               xsk_set_tx_need_wakeup(pool);
> +
> +       return sent == budget;
> +}
> +
>  static int virtnet_rq_bind_xsk_pool(struct virtnet_info *vi, struct virtnet_rq *rq,
>                                     struct xsk_buff_pool *pool)
>  {
> diff --git a/drivers/net/virtio/xsk.h b/drivers/net/virtio/xsk.h
> index 1918285c310c..73ca8cd5308b 100644
> --- a/drivers/net/virtio/xsk.h
> +++ b/drivers/net/virtio/xsk.h
> @@ -3,5 +3,18 @@
>  #ifndef __XSK_H__
>  #define __XSK_H__
>
> +#define VIRTIO_XSK_FLAG_OFFSET 4
> +
> +static inline void *virtnet_xsk_to_ptr(u32 len)
> +{
> +       unsigned long p;
> +
> +       p = len << VIRTIO_XSK_FLAG_OFFSET;
> +
> +       return (void *)(p | VIRTIO_XSK_FLAG);
> +}
> +
>  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);
>  #endif
> --
> 2.32.0.3.g01195cf9f
>


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