Subject: Re: [PATCH net-next v2 16/21] virtio_net: xsk: rx: introduce add_recvbuf_xsk()

From: "Michael S. Tsirkin" <[email-masked]>
Date: Thu, 9 Nov 2023 03:12:27 -0500

On Tue, Nov 07, 2023 at 11:12:22AM +0800, Xuan Zhuo wrote:
> Implement the logic of filling rq with XSK buffers.
> 
> Signed-off-by: Xuan Zhuo <[email-masked]>
> ---
>  drivers/net/virtio/main.c       |  4 ++-
>  drivers/net/virtio/virtio_net.h |  5 ++++
>  drivers/net/virtio/xsk.c        | 49 ++++++++++++++++++++++++++++++++-
>  drivers/net/virtio/xsk.h        |  2 ++
>  4 files changed, 58 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio/main.c b/drivers/net/virtio/main.c
> index 6210a6e37396..15943a22e17d 100644
> --- a/drivers/net/virtio/main.c
> +++ b/drivers/net/virtio/main.c
> @@ -1798,7 +1798,9 @@ static bool try_fill_recv(struct virtnet_info *vi, struct virtnet_rq *rq,
>  	bool oom;
>  
>  	do {
> -		if (vi->mergeable_rx_bufs)
> +		if (rq->xsk.pool)
> +			err = virtnet_add_recvbuf_xsk(vi, rq, rq->xsk.pool, gfp);
> +		else if (vi->mergeable_rx_bufs)
>  			err = add_recvbuf_mergeable(vi, rq, gfp);
>  		else if (vi->big_packets)
>  			err = add_recvbuf_big(vi, rq, gfp);

I'm not sure I understand. How does this handle mergeable flag still being set?

> diff --git a/drivers/net/virtio/virtio_net.h b/drivers/net/virtio/virtio_net.h
> index a13d6d301fdb..1242785e311e 100644
> --- a/drivers/net/virtio/virtio_net.h
> +++ b/drivers/net/virtio/virtio_net.h
> @@ -140,6 +140,11 @@ 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 ea5804ddd44e..e737c3353212 100644
> --- a/drivers/net/virtio/xsk.c
> +++ b/drivers/net/virtio/xsk.c
> @@ -38,6 +38,41 @@ static void virtnet_xsk_check_queue(struct virtnet_sq *sq)
>  		netif_stop_subqueue(dev, qnum);
>  }
>  
> +int virtnet_add_recvbuf_xsk(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;
> +	}

Another manually rolled linked list implementation.
Please, don't.

> +
> +	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;
> +}
> +
>  static int virtnet_xsk_xmit_one(struct virtnet_sq *sq,
>  				struct xsk_buff_pool *pool,
>  				struct xdp_desc *desc)
> @@ -213,7 +248,7 @@ 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.
> @@ -249,6 +284,16 @@ 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;
> @@ -307,6 +352,8 @@ static int virtnet_xsk_pool_disable(struct net_device *dev, u16 qid)
>  
>  	dma_unmap_single(dma_dev, sq->xsk.hdr_dma_address, vi->hdr_len, DMA_TO_DEVICE);
>  
> +	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