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Message-ID: <1727178087.972947-2-xuanzhuo@linux.alibaba.com>
Date: Tue, 24 Sep 2024 19:41:27 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: Jason Wang <jasowang@...hat.com>
Cc: netdev@...r.kernel.org,
"Michael S. Tsirkin" <mst@...hat.com>,
Eugenio Pérez <eperezma@...hat.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
virtualization@...ts.linux.dev,
bpf@...r.kernel.org
Subject: Re: [RFC net-next v1 10/12] virtio_net: xsk: tx: support xmit xsk buffer
On Tue, 24 Sep 2024 15:35:08 +0800, Jason Wang <jasowang@...hat.com> wrote:
> On Tue, Sep 24, 2024 at 9:32 AM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> 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.
> >
> > virtnet_free_old_xmit distinguishes three type ptr(skb, xdp frame, xsk
> > buffer) by the last bits of the pointer.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > ---
> > drivers/net/virtio_net.c | 176 ++++++++++++++++++++++++++++++++++++---
> > 1 file changed, 166 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 3ad4c6e3ef18..1a870f1df910 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -83,6 +83,7 @@ struct virtnet_sq_free_stats {
> > u64 bytes;
> > u64 napi_packets;
> > u64 napi_bytes;
> > + u64 xsk;
> > };
> >
> > struct virtnet_sq_stats {
> > @@ -514,16 +515,20 @@ static struct sk_buff *virtnet_skb_append_frag(struct sk_buff *head_skb,
> > struct sk_buff *curr_skb,
> > struct page *page, void *buf,
> > int len, int truesize);
> > +static void virtnet_xsk_completed(struct send_queue *sq, int num);
> >
> > enum virtnet_xmit_type {
> > VIRTNET_XMIT_TYPE_SKB,
> > VIRTNET_XMIT_TYPE_SKB_ORPHAN,
> > VIRTNET_XMIT_TYPE_XDP,
> > + VIRTNET_XMIT_TYPE_XSK,
> > };
> >
> > /* We use the last two bits of the pointer to distinguish the xmit type. */
> > #define VIRTNET_XMIT_TYPE_MASK (BIT(0) | BIT(1))
> >
> > +#define VIRTIO_XSK_FLAG_OFFSET 4
>
> Any reason this is not 2?
There's no particular reason for this, any value greater than 2 will work.
>
> > +
> > static enum virtnet_xmit_type virtnet_xmit_ptr_strip(void **ptr)
> > {
> > unsigned long p = (unsigned long)*ptr;
> > @@ -546,6 +551,11 @@ static int virtnet_add_outbuf(struct send_queue *sq, int num, void *data,
> > GFP_ATOMIC);
> > }
> >
> > +static u32 virtnet_ptr_to_xsk_buff_len(void *ptr)
> > +{
> > + return ((unsigned long)ptr) >> VIRTIO_XSK_FLAG_OFFSET;
> > +}
> > +
> > static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
> > {
> > sg_assign_page(sg, NULL);
> > @@ -587,11 +597,27 @@ 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_buff_len(ptr);
> > + stats->xsk++;
> > + break;
> > }
> > }
> > netdev_tx_completed_queue(txq, stats->napi_packets, stats->napi_bytes);
>
> Not related to this patch, but this seems unnecessary to AF_XDP.
YES.
netdev_tx_completed_queue will check napi_bytes firstly.
So I do not think we need to do anything for this.
>
> > }
> >
> > +static void virtnet_free_old_xmit(struct send_queue *sq,
> > + struct netdev_queue *txq,
> > + bool in_napi,
> > + struct virtnet_sq_free_stats *stats)
> > +{
> > + __free_old_xmit(sq, txq, in_napi, stats);
> > +
> > + if (stats->xsk)
> > + virtnet_xsk_completed(sq, stats->xsk);
> > +}
> > +
> > /* Converting between virtqueue no. and kernel tx/rx queue no.
> > * 0:rx0 1:tx0 2:rx1 3:tx1 ... 2N:rxN 2N+1:txN 2N+2:cvq
> > */
> > @@ -1019,7 +1045,7 @@ static void free_old_xmit(struct send_queue *sq, struct netdev_queue *txq,
> > {
> > struct virtnet_sq_free_stats stats = {0};
> >
> > - __free_old_xmit(sq, txq, in_napi, &stats);
> > + virtnet_free_old_xmit(sq, txq, in_napi, &stats);
> >
> > /* Avoid overhead when no packets have been processed
> > * happens when called speculatively from start_xmit.
> > @@ -1380,6 +1406,111 @@ static int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct receive_queue
> > return err;
> > }
> >
> > +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);
> > + break;
> > + }
> > +
> > + kick = true;
> > + }
> > +
> > + if (kick && virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq))
> > + (*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;
> > +
> > + /* Avoid to wakeup napi meanless, so call __free_old_xmit. */
>
> I don't understand the meaning of this comment.
The comments need to be more detailed. Here I want to explain why not just use
free_old_xmit.
>
> > + __free_old_xmit(sq, netdev_get_tx_queue(dev, sq - vi->sq), true, &stats);
> > +
> > + if (stats.xsk)
> > + xsk_tx_completed(sq->xsk_pool, stats.xsk);
> > +
> > + 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 void xsk_wakeup(struct send_queue *sq)
> > +{
> > + if (napi_if_scheduled_mark_missed(&sq->napi))
> > + return;
> > +
> > + local_bh_disable();
> > + virtqueue_napi_schedule(&sq->napi, sq->vq);
> > + local_bh_enable();
> > +}
> > +
> > static int virtnet_xsk_wakeup(struct net_device *dev, u32 qid, u32 flag)
> > {
> > struct virtnet_info *vi = netdev_priv(dev);
> > @@ -1393,14 +1524,19 @@ static int virtnet_xsk_wakeup(struct net_device *dev, u32 qid, u32 flag)
> >
> > sq = &vi->sq[qid];
> >
> > - if (napi_if_scheduled_mark_missed(&sq->napi))
> > - return 0;
> > + xsk_wakeup(sq);
> > + return 0;
> > +}
> >
> > - local_bh_disable();
> > - virtqueue_napi_schedule(&sq->napi, sq->vq);
> > - local_bh_enable();
> > +static void virtnet_xsk_completed(struct send_queue *sq, int num)
> > +{
> > + xsk_tx_completed(sq->xsk_pool, num);
> >
> > - return 0;
> > + /* If this is called by rx poll, start_xmit and xdp xmit we should
> > + * wakeup the tx napi to consume the xsk tx queue, because the tx
> > + * interrupt may not be triggered.
> > + */
> > + xsk_wakeup(sq);
> > }
> >
> > static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
> > @@ -1516,8 +1652,8 @@ static int virtnet_xdp_xmit(struct net_device *dev,
> > }
> >
> > /* Free up any pending old buffers before queueing new ones. */
> > - __free_old_xmit(sq, netdev_get_tx_queue(dev, sq - vi->sq),
> > - false, &stats);
> > + virtnet_free_old_xmit(sq, netdev_get_tx_queue(dev, sq - vi->sq),
> > + false, &stats);
> >
> > for (i = 0; i < n; i++) {
> > struct xdp_frame *xdpf = frames[i];
> > @@ -2961,6 +3097,7 @@ 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;
> >
> > @@ -2973,7 +3110,11 @@ 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);
>
> I think we need a better name of "xsk_busy", it looks like it means we
> exceeds the quota. Or just return the number of buffers received and
> let the caller to judge.
Will fix.
Thanks.
>
> Other looks good.
>
> With this fixed.
>
> Acked-by: Jason Wang <jasowang@...hat.com>
>
> Thanks
>
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