Re: [PATCH net-next v5 11/15] virtio_net: xsk: tx: support xmit xsk buffer

[Jason Wang <jasowang@redhat.com>]

On Mon, Jun 17, 2024 at 3:54 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>
> On Mon, 17 Jun 2024 14:30:07 +0800, Jason Wang <jasowang@redhat.com> wrote:
> > On Fri, Jun 14, 2024 at 2:40 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_net.c | 121 ++++++++++++++++++++++++++++++++++++++-
> > >  1 file changed, 119 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index 2767338dc060..7e811f392768 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -535,10 +535,13 @@ enum virtnet_xmit_type {
> > >         VIRTNET_XMIT_TYPE_SKB,
> > >         VIRTNET_XMIT_TYPE_XDP,
> > >         VIRTNET_XMIT_TYPE_DMA,
> > > +       VIRTNET_XMIT_TYPE_XSK,
> > >  };
> > >
> > >  #define VIRTNET_XMIT_TYPE_MASK (VIRTNET_XMIT_TYPE_SKB | VIRTNET_XMIT_TYPE_XDP \
> > > -                               | VIRTNET_XMIT_TYPE_DMA)
> > > +                               | VIRTNET_XMIT_TYPE_DMA | VIRTNET_XMIT_TYPE_XSK)
> > > +
> > > +#define VIRTIO_XSK_FLAG_OFFSET 4
> > >
> > >  static enum virtnet_xmit_type virtnet_xmit_ptr_strip(void **ptr)
> > >  {
> > > @@ -768,6 +771,10 @@ static void __free_old_xmit(struct send_queue *sq, bool in_napi,
> > >                          * func again.
> > >                          */
> > >                         goto retry;
> > > +
> > > +               case VIRTNET_XMIT_TYPE_XSK:
> > > +                       /* Make gcc happy. DONE in subsequent commit */
> >
> > This is probably a hint that the next patch should be squashed here.
>
> The code for the xmit patch is more. So I separate the code out.
>
> >
> > > +                       break;
> > >                 }
> > >         }
> > >  }
> > > @@ -1265,6 +1272,102 @@ static void check_sq_full_and_disable(struct virtnet_info *vi,
> > >         }
> > >  }
> > >
> > > +static void *virtnet_xsk_to_ptr(u32 len)
> > > +{
> > > +       unsigned long p;
> > > +
> > > +       p = len << VIRTIO_XSK_FLAG_OFFSET;
> > > +
> > > +       return virtnet_xmit_ptr_mix((void *)p, VIRTNET_XMIT_TYPE_XSK);
> > > +}
> > > +
> > > +static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
> > > +{
> > > +       sg->dma_address = addr;
> > > +       sg->length = len;
> > > +}
> > > +
> > > +static int virtnet_xsk_xmit_one(struct send_queue *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 send_queue *sq,
> > > +                                 struct xsk_buff_pool *pool,
> > > +                                 unsigned int budget,
> > > +                                 u64 *kicks)
> > > +{
> > > +       struct xdp_desc *descs = pool->tx_descs;
> > > +       bool kick = false;
> > > +       u32 nb_pkts, i;
> > > +       int err;
> > > +
> > > +       budget = min_t(u32, budget, sq->vq->num_free);
> > > +
> > > +       nb_pkts = xsk_tx_peek_release_desc_batch(pool, budget);
> > > +       if (!nb_pkts)
> > > +               return 0;
> > > +
> > > +       for (i = 0; i < nb_pkts; i++) {
> > > +               err = virtnet_xsk_xmit_one(sq, pool, &descs[i]);
> > > +               if (unlikely(err)) {
> > > +                       xsk_tx_completed(sq->xsk.pool, nb_pkts - i);
> > > +                       break;
> >
> > Any reason we don't need a kick here?
>
> After the loop, I checked the kick.
>
> Do you mean kick for the packet that encountered the error?

Nope, I mis-read the code but kick is actually i == 0 here.

>
>
> >
> > > +               }
> > > +
> > > +               kick = true;
> > > +       }
> > > +
> > > +       if (kick && virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq))
> > > +               (*kicks)++;
> > > +
> > > +       return i;
> > > +}
> > > +
> > > +static bool virtnet_xsk_xmit(struct send_queue *sq, struct xsk_buff_pool *pool,
> > > +                            int budget)
> > > +{
> > > +       struct virtnet_info *vi = sq->vq->vdev->priv;
> > > +       struct virtnet_sq_free_stats stats = {};
> > > +       u64 kicks = 0;
> > > +       int sent;
> > > +
> > > +       __free_old_xmit(sq, true, &stats);
> > > +
> > > +       sent = virtnet_xsk_xmit_batch(sq, pool, budget, &kicks);
> > > +
> > > +       if (!is_xdp_raw_buffer_queue(vi, sq - vi->sq))
> > > +               check_sq_full_and_disable(vi, vi->dev, sq);
> > > +
> > > +       u64_stats_update_begin(&sq->stats.syncp);
> > > +       u64_stats_add(&sq->stats.packets, stats.packets);
> > > +       u64_stats_add(&sq->stats.bytes,   stats.bytes);
> > > +       u64_stats_add(&sq->stats.kicks,   kicks);
> > > +       u64_stats_add(&sq->stats.xdp_tx,  sent);
> > > +       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_xdp_xmit_one(struct virtnet_info *vi,
> > >                                    struct send_queue *sq,
> > >                                    struct xdp_frame *xdpf)
> > > @@ -2707,6 +2810,7 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
> > >         struct virtnet_info *vi = sq->vq->vdev->priv;
> > >         unsigned int index = vq2txq(sq->vq);
> > >         struct netdev_queue *txq;
> > > +       bool xsk_busy = false;
> > >         int opaque;
> > >         bool done;
> > >
> > > @@ -2719,7 +2823,11 @@ 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);
> > > +
> > > +       if (sq->xsk.pool)
> > > +               xsk_busy = virtnet_xsk_xmit(sq, sq->xsk.pool, budget);
> >
> > How about rename this to "xsk_sent"?
>
>
> OK
>
> Thanks.
>
>
> >
> > > +       else
> > > +               free_old_xmit(sq, true);
> > >
> > >         if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) {
> > >                 if (netif_tx_queue_stopped(txq)) {
> > > @@ -2730,6 +2838,11 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
> > >                 netif_tx_wake_queue(txq);
> > >         }
> > >
> > > +       if (xsk_busy) {
> > > +               __netif_tx_unlock(txq);
> > > +               return budget;
> > > +       }
> > > +
> > >         opaque = virtqueue_enable_cb_prepare(sq->vq);
> > >
> > >         done = napi_complete_done(napi, 0);
> > > @@ -5715,6 +5828,10 @@ static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf)
> > >         case VIRTNET_XMIT_TYPE_DMA:
> > >                 virtnet_sq_unmap(sq, &buf);
> > >                 goto retry;
> > > +
> > > +       case VIRTNET_XMIT_TYPE_XSK:
> > > +               /* Make gcc happy. DONE in subsequent commit */
> > > +               break;
> > >         }
> > >  }
> > >
> > > --
> > > 2.32.0.3.g01195cf9f
> > >
> >
> > Thanks
> >
>