Re: [PATCH net-next v2 12/21] virtio_net: xsk: tx: support tx

Michael S. Tsirkin
2023-11-09T08:09:10Z

On Tue, Nov 07, 2023 at 11:12:18AM +0800, Xuan Zhuo 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/main.c | 12 +++-
> drivers/net/virtio/virtio_net.h | 3 +-
> drivers/net/virtio/xsk.c | 110 ++++++++++++++++++++++++++++++++
> drivers/net/virtio/xsk.h | 13 ++++
> 4 files changed, 136 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio/main.c b/drivers/net/virtio/main.c
> index 6c608b3ce27d..ff6bc764089d 100644
> --- a/drivers/net/virtio/main.c
> +++ b/drivers/net/virtio/main.c
> @@ -2074,6 +2074,7 @@ 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;
> + int busy = 0;
> int opaque;
> bool done;
>
> @@ -2086,11 +2087,20 @@ 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)
> + busy |= virtnet_xsk_xmit(sq, sq->xsk.pool, budget);

You use bitwise or on errno values? What's going on here?

> + else
> + free_old_xmit(sq, true);
>
> if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
> netif_tx_wake_queue(txq);
>
> + if (busy) {
> + __netif_tx_unlock(txq);
> + return budget;
> + }
> +
> opaque = virtqueue_enable_cb_prepare(sq->vq);
>
> done = napi_complete_done(napi, 0);
> diff --git a/drivers/net/virtio/virtio_net.h b/drivers/net/virtio/virtio_net.h
> index 442af4673bf8..1c21af47e13c 100644
> --- a/drivers/net/virtio/virtio_net.h
> +++ b/drivers/net/virtio/virtio_net.h
> @@ -9,7 +9,8 @@
> #include <net/xdp_sock_drv.h>
>
> #define VIRTIO_XDP_FLAG BIT(0)
> -#define VIRTIO_XMIT_DATA_MASK (VIRTIO_XDP_FLAG)
> +#define VIRTIO_XSK_FLAG BIT(1)
> +#define VIRTIO_XMIT_DATA_MASK (VIRTIO_XDP_FLAG | VIRTIO_XSK_FLAG)
>
> /* RX packet size EWMA. The average packet size is used to determine the packet
> * buffer size when refilling RX rings. As the entire RX ring may be refilled
> diff --git a/drivers/net/virtio/xsk.c b/drivers/net/virtio/xsk.c
> index 8b397787603f..caa448308232 100644
> --- a/drivers/net/virtio/xsk.c
> +++ b/drivers/net/virtio/xsk.c
> @@ -4,9 +4,119 @@
> */
>
> #include "virtio_net.h"
> +#include "xsk.h"
>
> static struct virtio_net_hdr_mrg_rxbuf xsk_hdr;
>
> +static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
> +{
> + sg->dma_address = addr;
> + sg->length = len;
> +}
> +
> +static void virtnet_xsk_check_queue(struct virtnet_sq *sq)
> +{
> + struct virtnet_info *vi = sq->vq->vdev->priv;
> + struct net_device *dev = vi->dev;
> + int qnum = sq - vi->sq;
> +
> + /* If it is a raw buffer queue, it does not check whether the status
> + * of the queue is stopped when sending. So there is no need to check
> + * the situation of the raw buffer queue.
> + */
> + if (virtnet_is_xdp_raw_buffer_queue(vi, qnum))
> + return;
> +
> + /* If this sq is not the exclusive queue of the current cpu,
> + * then it may be called by start_xmit, so check it running out
> + * of space.
> + *
> + * Stop the queue to avoid getting packets that we are
> + * then unable to transmit. Then wait the tx interrupt.
> + */
> + if (sq->vq->num_free < 2 + MAX_SKB_FRAGS)

what does MAX_SKB_FRAGS have to do with it? And where's 2 coming from?

> + netif_stop_subqueue(dev, qnum);
> +}
> +
> +static int virtnet_xsk_xmit_one(struct virtnet_sq *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 virtnet_sq *sq,
> + struct xsk_buff_pool *pool,
> + unsigned int budget,
> + u64 *kicks)
> +{
> + struct xdp_desc *descs = pool->tx_descs;
> + u32 nb_pkts, max_pkts, i;
> + bool kick = false;
> + int err;
> +
> + /* Every xsk tx packet needs two desc(virtnet header and packet). So we
> + * use sq->vq->num_free / 2 as the limitation.
> + */
> + max_pkts = min_t(u32, budget, sq->vq->num_free / 2);
> +
> + nb_pkts = xsk_tx_peek_release_desc_batch(pool, max_pkts);
> + if (!nb_pkts)
> + return 0;
> +
> + for (i = 0; i < nb_pkts; i++) {
> + err = virtnet_xsk_xmit_one(sq, pool, &descs[i]);
> + if (unlikely(err))
> + break;
> +
> + kick = true;
> + }
> +
> + if (kick && virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq))
> + (*kicks)++;
> +
> + return i;
> +}
> +
> +bool virtnet_xsk_xmit(struct virtnet_sq *sq, struct xsk_buff_pool *pool,
> + int budget)
> +{
> + u64 bytes = 0, packets = 0, kicks = 0;
> + int sent;
> +
> + virtnet_free_old_xmit(sq, true, &bytes, &packets);
> +
> + sent = virtnet_xsk_xmit_batch(sq, pool, budget, &kicks);
> +
> + virtnet_xsk_check_queue(sq);
> +
> + u64_stats_update_begin(&sq->stats.syncp);
> + u64_stats_add(&sq->stats.packets, packets);
> + u64_stats_add(&sq->stats.bytes, 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_rq_bind_xsk_pool(struct virtnet_info *vi, struct virtnet_rq *rq,
> struct xsk_buff_pool *pool)
> {
> diff --git a/drivers/net/virtio/xsk.h b/drivers/net/virtio/xsk.h
> index 1918285c310c..73ca8cd5308b 100644
> --- a/drivers/net/virtio/xsk.h
> +++ b/drivers/net/virtio/xsk.h
> @@ -3,5 +3,18 @@
> #ifndef __XSK_H__
> #define __XSK_H__
>
> +#define VIRTIO_XSK_FLAG_OFFSET 4
> +
> +static inline void *virtnet_xsk_to_ptr(u32 len)
> +{
> + unsigned long p;
> +
> + p = len << VIRTIO_XSK_FLAG_OFFSET;
> +
> + return (void *)(p | VIRTIO_XSK_FLAG);
> +}
> +
> 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);
> #endif
> --
> 2.32.0.3.g01195cf9f