Re: [PATCH net-next v1 11/19] virtio_net: xsk: tx: support tx

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Fri, 20 Oct 2023 14:52:08 +0800, Jason Wang <jasowang@redhat.com> wrote:
> On Mon, Oct 16, 2023 at 8:01 PM Xuan Zhuo <xuanzhuo@linux.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@linux.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.

Will fix.

Thanks.


>
> 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
> >
>