On Wed, 11 Sep 2024 12:31:32 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
> On Tue, Aug 20, 2024 at 3:33 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxx>
> > ---
> > drivers/net/virtio_net.c | 127 ++++++++++++++++++++++++++++++++++++++-
> > 1 file changed, 125 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 221681926d23..3743694d3c3b 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -516,10 +516,13 @@ enum virtnet_xmit_type {
> > VIRTNET_XMIT_TYPE_SKB,
> > VIRTNET_XMIT_TYPE_ORPHAN,
> > VIRTNET_XMIT_TYPE_XDP,
> > + VIRTNET_XMIT_TYPE_XSK,
> > };
> >
> > #define VIRTNET_XMIT_TYPE_MASK (VIRTNET_XMIT_TYPE_SKB | VIRTNET_XMIT_TYPE_ORPHAN \
> > - | VIRTNET_XMIT_TYPE_XDP)
> > + | VIRTNET_XMIT_TYPE_XDP | VIRTNET_XMIT_TYPE_XSK)
> > +
> > +#define VIRTIO_XSK_FLAG_OFFSET 4
> >
> > static enum virtnet_xmit_type virtnet_xmit_ptr_strip(void **ptr)
> > {
> > @@ -543,6 +546,11 @@ static int virtnet_add_outbuf(struct send_queue *sq, int num, void *data,
> > GFP_ATOMIC);
> > }
> >
> > +static u32 virtnet_ptr_to_xsk(void *ptr)
> > +{
> > + return ((unsigned long)ptr) >> VIRTIO_XSK_FLAG_OFFSET;
> > +}
> > +
>
> This needs a better name, otherwise readers might be confused.
>
> E.g something like virtnet_ptr_to_xsk_buff_len()?
>
> > static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
> > {
> > sg_assign_page(sg, NULL);
> > @@ -584,6 +592,10 @@ static void __free_old_xmit(struct send_queue *sq, struct netdev_queue *txq,
> > stats->bytes += xdp_get_frame_len(frame);
> > xdp_return_frame(frame);
> > break;
> > +
> > + case VIRTNET_XMIT_TYPE_XSK:
> > + stats->bytes += virtnet_ptr_to_xsk(ptr);
> > + break;
>
> Do we miss xsk_tx_completed() here?
>
> > }
> > }
> > netdev_tx_completed_queue(txq, stats->napi_packets, stats->napi_bytes);
> > @@ -1393,6 +1405,97 @@ static int virtnet_xsk_wakeup(struct net_device *dev, u32 qid, u32 flag)
> > return 0;
> > }
> >
> > +static void *virtnet_xsk_to_ptr(u32 len)
> > +{
> > + unsigned long p;
> > +
> > + p = len << VIRTIO_XSK_FLAG_OFFSET;
> > +
> > + return virtnet_xmit_ptr_mix((void *)p, VIRTNET_XMIT_TYPE_XSK);
> > +}
> > +
> > +static int virtnet_xsk_xmit_one(struct send_queue *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_addr, 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 send_queue *sq,
> > + struct xsk_buff_pool *pool,
> > + unsigned int budget,
> > + u64 *kicks)
> > +{
> > + struct xdp_desc *descs = pool->tx_descs;
> > + bool kick = false;
> > + u32 nb_pkts, i;
> > + int err;
> > +
> > + budget = min_t(u32, budget, sq->vq->num_free);
> > +
> > + nb_pkts = xsk_tx_peek_release_desc_batch(pool, budget);
> > + if (!nb_pkts)
> > + return 0;
> > +
> > + for (i = 0; i < nb_pkts; i++) {
> > + err = virtnet_xsk_xmit_one(sq, pool, &descs[i]);
> > + if (unlikely(err)) {
> > + xsk_tx_completed(sq->xsk_pool, nb_pkts - i);
>
> Should we kick in this condition?
>
> > + break;
> > + }
> > +
> > + kick = true;
> > + }
> > +
> > + if (kick && virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq))
>
> Can we simply use virtqueue_kick() here?
>
> > + (*kicks)++;
> > +
> > + return i;
> > +}
> > +
> > +static bool virtnet_xsk_xmit(struct send_queue *sq, struct xsk_buff_pool *pool,
> > + int budget)
> > +{
> > + struct virtnet_info *vi = sq->vq->vdev->priv;
> > + struct virtnet_sq_free_stats stats = {};
> > + struct net_device *dev = vi->dev;
> > + u64 kicks = 0;
> > + int sent;
> > +
> > + __free_old_xmit(sq, netdev_get_tx_queue(dev, sq - vi->sq), true, &stats);
>
> I haven't checked in depth, but I wonder if we have some side effects
> when using non NAPI tx mode:
>
> if (napi->weight)
> virtqueue_napi_schedule(napi, vq);
> else
> /* We were probably waiting for more output buffers. */
> netif_wake_subqueue(vi->dev, vq2txq(vq));
>
> Does this mean xsk will suffer the same issue like when there's no xsk
> xmit request, we could end up with no way to reclaim xmitted xsk
> buffers? (Or should we disallow AF_XDP to be used for non TX-NAPI
> mode?)
Disallow AF_XDP to be used for non TX-NAPI mode.
The last patch #9 does this.
#9 [PATCH net-next 09/13] virtio_net: xsk: prevent disable tx napi
Thanks.
>
> > +
> > + sent = virtnet_xsk_xmit_batch(sq, pool, budget, &kicks);
> > +
> > + if (!is_xdp_raw_buffer_queue(vi, sq - vi->sq))
> > + check_sq_full_and_disable(vi, vi->dev, sq);
> > +
> > + u64_stats_update_begin(&sq->stats.syncp);
> > + u64_stats_add(&sq->stats.packets, stats.packets);
> > + u64_stats_add(&sq->stats.bytes, stats.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_xdp_xmit_one(struct virtnet_info *vi,
> > struct send_queue *sq,
> > struct xdp_frame *xdpf)
> > @@ -2949,6 +3052,7 @@ 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;
> > + bool xsk_busy = false;
> > int opaque;
> > bool done;
> >
> > @@ -2961,7 +3065,11 @@ 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, txq, !!budget);
> > +
> > + if (sq->xsk_pool)
> > + xsk_busy = virtnet_xsk_xmit(sq, sq->xsk_pool, budget);
> > + else
> > + free_old_xmit(sq, txq, !!budget);
> >
> > if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) {
> > if (netif_tx_queue_stopped(txq)) {
> > @@ -2972,6 +3080,11 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
> > netif_tx_wake_queue(txq);
> > }
> >
> > + if (xsk_busy) {
> > + __netif_tx_unlock(txq);
> > + return budget;
> > + }
> > +
> > opaque = virtqueue_enable_cb_prepare(sq->vq);
> >
> > done = napi_complete_done(napi, 0);
> > @@ -5974,6 +6087,12 @@ static void free_receive_page_frags(struct virtnet_info *vi)
> >
> > static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf)
> > {
> > + struct virtnet_info *vi = vq->vdev->priv;
> > + struct send_queue *sq;
> > + int i = vq2rxq(vq);
> > +
> > + sq = &vi->sq[i];
> > +
> > switch (virtnet_xmit_ptr_strip(&buf)) {
> > case VIRTNET_XMIT_TYPE_SKB:
> > case VIRTNET_XMIT_TYPE_ORPHAN:
> > @@ -5983,6 +6102,10 @@ static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf)
> > case VIRTNET_XMIT_TYPE_XDP:
> > xdp_return_frame(buf);
> > break;
> > +
> > + case VIRTNET_XMIT_TYPE_XSK:
> > + xsk_tx_completed(sq->xsk_pool, 1);
> > + break;
> > }
> > }
> >
> > --
> > 2.32.0.3.g01195cf9f
> >
>
> Thanks
>
