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

Xuan Zhuo
2023-11-09T11:09:11Z

On Thu, 9 Nov 2023 03:09:00 -0500, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 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?

virtnet_xsk_xmit() return that it is busy or not. Not the errno.
Here just record whether this handler is busy or not.

>
>
> > + 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?

check_sq_full_and_disable()

Thanks.

>
> > + 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
>