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Date: Mon, 23 Oct 2023 14:56:52 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: Jason Wang <jasowang@...hat.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 15/19] virtio_net: xsk: rx: introduce add_recvbuf_xsk()

On Fri, 20 Oct 2023 14:56:51 +0800, Jason Wang <jasowang@...hat.com> wrote:
> On Mon, Oct 16, 2023 at 8:01 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> >
> > Implement the logic of filling vq with XSK buffer.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.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?


YES. we synchronize the rx_pause and this.

But for the rcu object, I think we should use rcu_xxx() API.

Thanks.


>
> 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
> >
>

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