Re: [PATCH net-next v5 09/15] virtio_net: xsk: bind/unbind xsk

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

On Tue, 18 Jun 2024 09:04:03 +0800, Jason Wang <jasowang@redhat.com> wrote:
> On Mon, Jun 17, 2024 at 3:49 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> >
> > On Mon, 17 Jun 2024 14:19:10 +0800, Jason Wang <jasowang@redhat.com> wrote:
> > > On Fri, Jun 14, 2024 at 2:39 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> > > >
> > > > This patch implement the logic of bind/unbind xsk pool to sq and rq.
> > > >
> > > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > > ---
> > > >  drivers/net/virtio_net.c | 201 ++++++++++++++++++++++++++++++++++++++-
> > > >  1 file changed, 200 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > index 88ab9ea1646f..35fd8bca7fcf 100644
> > > > --- a/drivers/net/virtio_net.c
> > > > +++ b/drivers/net/virtio_net.c
> > > > @@ -26,6 +26,7 @@
> > > >  #include <net/netdev_rx_queue.h>
> > > >  #include <net/netdev_queues.h>
> > > >  #include <uapi/linux/virtio_ring.h>
> > > > +#include <net/xdp_sock_drv.h>
> > > >
> > > >  static int napi_weight = NAPI_POLL_WEIGHT;
> > > >  module_param(napi_weight, int, 0444);
> > > > @@ -57,6 +58,8 @@ DECLARE_EWMA(pkt_len, 0, 64)
> > > >
> > > >  #define VIRTNET_DRIVER_VERSION "1.0.0"
> > > >
> > > > +static struct virtio_net_hdr_mrg_rxbuf xsk_hdr;
> > >
> > > Does this mean AF_XDP only supports virtio_net_hdr_mrg_rxbuf but not others?
> >
> > Sorry, this is the old code.
> >
> > Should be virtio_net_common_hdr.
> >
> > Here we should use the max size of the virtio-net header.
>
> Better but still suboptimal, for example it could be extended as we're
> adding more features?

When we use this, we will work with hdr_len.

	sg_fill_dma(sq->sg, sq->xsk.hdr_dma_address, vi->hdr_len);

So, I think it is ok.

>
> >
> > >
> > > > +
> > > >  static const unsigned long guest_offloads[] = {
> > > >         VIRTIO_NET_F_GUEST_TSO4,
> > > >         VIRTIO_NET_F_GUEST_TSO6,
> > > > @@ -321,6 +324,12 @@ struct send_queue {
> > > >         bool premapped;
> > > >
> > > >         struct virtnet_sq_dma_info dmainfo;
> > > > +
> > > > +       struct {
> > > > +               struct xsk_buff_pool *pool;
> > > > +
> > > > +               dma_addr_t hdr_dma_address;
> > > > +       } xsk;
> > > >  };
> > > >
> > > >  /* Internal representation of a receive virtqueue */
> > > > @@ -372,6 +381,13 @@ struct receive_queue {
> > > >
> > > >         /* Record the last dma info to free after new pages is allocated. */
> > > >         struct virtnet_rq_dma *last_dma;
> > > > +
> > > > +       struct {
> > > > +               struct xsk_buff_pool *pool;
> > > > +
> > > > +               /* xdp rxq used by xsk */
> > > > +               struct xdp_rxq_info xdp_rxq;
> > > > +       } xsk;
> > > >  };
> > > >
> > > >  /* This structure can contain rss message with maximum settings for indirection table and keysize
> > > > @@ -695,7 +711,7 @@ static void virtnet_sq_free_dma_meta(struct send_queue *sq)
> > > >  /* This function must be called immediately after creating the vq, or after vq
> > > >   * reset, and before adding any buffers to it.
> > > >   */
> > > > -static __maybe_unused int virtnet_sq_set_premapped(struct send_queue *sq, bool premapped)
> > > > +static int virtnet_sq_set_premapped(struct send_queue *sq, bool premapped)
> > > >  {
> > > >         if (premapped) {
> > > >                 int r;
> > > > @@ -5177,6 +5193,187 @@ static int virtnet_restore_guest_offloads(struct virtnet_info *vi)
> > > >         return virtnet_set_guest_offloads(vi, offloads);
> > > >  }
> > > >
> > > > +static int virtnet_rq_bind_xsk_pool(struct virtnet_info *vi, struct receive_queue *rq,
> > > > +                                   struct xsk_buff_pool *pool)
> > > > +{
> > > > +       int err, qindex;
> > > > +
> > > > +       qindex = rq - vi->rq;
> > > > +
> > > > +       if (pool) {
> > > > +               err = xdp_rxq_info_reg(&rq->xsk.xdp_rxq, vi->dev, qindex, rq->napi.napi_id);
> > > > +               if (err < 0)
> > > > +                       return err;
> > > > +
> > > > +               err = xdp_rxq_info_reg_mem_model(&rq->xsk.xdp_rxq,
> > > > +                                                MEM_TYPE_XSK_BUFF_POOL, NULL);
> > > > +               if (err < 0) {
> > > > +                       xdp_rxq_info_unreg(&rq->xsk.xdp_rxq);
> > > > +                       return err;
> > > > +               }
> > > > +
> > > > +               xsk_pool_set_rxq_info(pool, &rq->xsk.xdp_rxq);
> > > > +       }
> > > > +
> > > > +       virtnet_rx_pause(vi, rq);
> > > > +
> > > > +       err = virtqueue_reset(rq->vq, virtnet_rq_unmap_free_buf);
> > > > +       if (err) {
> > > > +               netdev_err(vi->dev, "reset rx fail: rx queue index: %d err: %d\n", qindex, err);
> > > > +
> > > > +               pool = NULL;
> > > > +       }
> > > > +
> > > > +       if (!pool)
> > > > +               xdp_rxq_info_unreg(&rq->xsk.xdp_rxq);
> > >
> > > Let's use err label instead of duplicating xdp_rxq_info_unreg() here?
> > >
> > > > +
> > > > +       rq->xsk.pool = pool;
> > > > +
> > > > +       virtnet_rx_resume(vi, rq);
> > > > +
> > > > +       return err;
> > > > +}
> > > > +
> > > > +static int virtnet_sq_bind_xsk_pool(struct virtnet_info *vi,
> > > > +                                   struct send_queue *sq,
> > > > +                                   struct xsk_buff_pool *pool)
> > > > +{
> > > > +       int err, qindex;
> > > > +
> > > > +       qindex = sq - vi->sq;
> > > > +
> > > > +       virtnet_tx_pause(vi, sq);
> > > > +
> > > > +       err = virtqueue_reset(sq->vq, virtnet_sq_free_unused_buf);
> > > > +       if (err)
> > > > +               netdev_err(vi->dev, "reset tx fail: tx queue index: %d err: %d\n", qindex, err);
> > > > +       else
> > > > +               err = virtnet_sq_set_premapped(sq, !!pool);
> > > > +
> > > > +       if (err)
> > > > +               pool = NULL;
> > > > +
> > > > +       sq->xsk.pool = pool;
> > > > +
> > > > +       virtnet_tx_resume(vi, sq);
> > > > +
> > > > +       return err;
> > > > +}
> > > > +
> > > > +static int virtnet_xsk_pool_enable(struct net_device *dev,
> > > > +                                  struct xsk_buff_pool *pool,
> > > > +                                  u16 qid)
> > > > +{
> > > > +       struct virtnet_info *vi = netdev_priv(dev);
> > > > +       struct receive_queue *rq;
> > > > +       struct send_queue *sq;
> > > > +       struct device *dma_dev;
> > > > +       dma_addr_t hdr_dma;
> > > > +       int err;
> > > > +
> > > > +       /* In big_packets mode, xdp cannot work, so there is no need to
> > > > +        * initialize xsk of rq.
> > > > +        *
> > > > +        * Support for small mode firstly.
> > >
> > > This comment is kind of confusing, I think mergeable mode is also
> > > supported. If it's true, we can simply remove it.
> >
> > For the commit num limit of the net-next, I have to remove some commits.
> >
> > So the mergeable mode is not supported by this patch set.
> >
> > I plan to support the merge mode after this patch set.
>
> Then, I'd suggest to split the patches into two series:
>
> 1) AF_XDP TX zerocopy
> 2) AF_XDP RX zerocopy
>
> And implement both small and mergeable in series 2).


I am ok.


>
> >
> >
> > >
> > > > +        */
> > > > +       if (vi->big_packets)
> > > > +               return -ENOENT;
> > > > +
> > > > +       if (qid >= vi->curr_queue_pairs)
> > > > +               return -EINVAL;
> > > > +
> > > > +       sq = &vi->sq[qid];
> > > > +       rq = &vi->rq[qid];
> > > > +
> > > > +       /* xsk tx zerocopy depend on the tx napi.
> > > > +        *
> > > > +        * All xsk packets are actually consumed and sent out from the xsk tx
> > > > +        * queue under the tx napi mechanism.
> > > > +        */
> > > > +       if (!sq->napi.weight)
> > > > +               return -EPERM;
> > > > +
> > > > +       /* For the xsk, the tx and rx should have the same device. But
> > > > +        * vq->dma_dev allows every vq has the respective dma dev. So I check
> > > > +        * the dma dev of vq and sq is the same dev.
> > > > +        */
> > > > +       if (virtqueue_dma_dev(rq->vq) != virtqueue_dma_dev(sq->vq))
> > > > +               return -EPERM;
> > >
> > > I don't understand how a different DMA device matters here. It looks
> > > like the code is using per virtqueue DMA below.
> >
> > The af-xdp may use one buffer to receive from the rx and reuse this buffer to
> > send by the tx.  So the dma dev of sq and rq should be the same one.
>
> Right, let's tweak the comment to say something like this.

Will fix.

Thanks.


>
> Thanks
>