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

[Jason Wang <jasowang@redhat.com>]

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?

> +
>  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.

> +        */
> +       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.

> +
> +       dma_dev = virtqueue_dma_dev(rq->vq);
> +       if (!dma_dev)
> +               return -EPERM;
> +
> +       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;
> +
> +       err = xsk_pool_dma_map(pool, dma_dev, 0);
> +       if (err)
> +               goto err_xsk_map;
> +
> +       err = virtnet_rq_bind_xsk_pool(vi, rq, pool);
> +       if (err)
> +               goto err_rq;
> +
> +       err = virtnet_sq_bind_xsk_pool(vi, sq, pool);
> +       if (err)
> +               goto err_sq;
> +
> +       /* Now, we do not support tx offset, so all the tx virtnet hdr is zero.
> +        * So all the tx packets can share a single hdr.
> +        */
> +       sq->xsk.hdr_dma_address = hdr_dma;
> +
> +       return 0;
> +
> +err_sq:
> +       virtnet_rq_bind_xsk_pool(vi, rq, NULL);
> +err_rq:
> +       xsk_pool_dma_unmap(pool, 0);
> +err_xsk_map:
> +       dma_unmap_single(dma_dev, hdr_dma, vi->hdr_len, DMA_TO_DEVICE);
> +       return err;
> +}
> +
> +static int virtnet_xsk_pool_disable(struct net_device *dev, u16 qid)
> +{
> +       struct virtnet_info *vi = netdev_priv(dev);
> +       struct xsk_buff_pool *pool;
> +       struct device *dma_dev;
> +       struct receive_queue *rq;
> +       struct send_queue *sq;
> +       int err1, err2;
> +
> +       if (qid >= vi->curr_queue_pairs)
> +               return -EINVAL;
> +
> +       sq = &vi->sq[qid];
> +       rq = &vi->rq[qid];
> +
> +       pool = sq->xsk.pool;
> +
> +       err1 = virtnet_sq_bind_xsk_pool(vi, sq, NULL);
> +       err2 = virtnet_rq_bind_xsk_pool(vi, rq, NULL);
> +
> +       xsk_pool_dma_unmap(pool, 0);
> +
> +       dma_dev = virtqueue_dma_dev(rq->vq);
> +
> +       dma_unmap_single(dma_dev, sq->xsk.hdr_dma_address, vi->hdr_len, DMA_TO_DEVICE);
> +
> +       return err1 | err2;
> +}
> +
> +static int virtnet_xsk_pool_setup(struct net_device *dev, struct netdev_bpf *xdp)
> +{
> +       if (xdp->xsk.pool)
> +               return virtnet_xsk_pool_enable(dev, xdp->xsk.pool,
> +                                              xdp->xsk.queue_id);
> +       else
> +               return virtnet_xsk_pool_disable(dev, xdp->xsk.queue_id);
> +}
> +
>  static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
>                            struct netlink_ext_ack *extack)
>  {
> @@ -5302,6 +5499,8 @@ static int virtnet_xdp(struct net_device *dev, struct netdev_bpf *xdp)
>         switch (xdp->command) {
>         case XDP_SETUP_PROG:
>                 return virtnet_xdp_set(dev, xdp->prog, xdp->extack);
> +       case XDP_SETUP_XSK_POOL:
> +               return virtnet_xsk_pool_setup(dev, xdp);
>         default:
>                 return -EINVAL;
>         }
> --
> 2.32.0.3.g01195cf9f
>

Thanks