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Message-ID: <CACGkMEtgWw9J4Y8fQCWY4ED_=Bdi6ArmOMMA2OjyGbOOu90OTg@mail.gmail.com>
Date: Fri, 13 Sep 2024 11:21:21 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.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: [PATCH net-next 10/13] virtio_net: xsk: tx: support xmit xsk buffer
On Thu, Sep 12, 2024 at 4:50 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> On Wed, 11 Sep 2024 12:31:32 +0800, Jason Wang <jasowang@...hat.com> wrote:
> > On Tue, Aug 20, 2024 at 3:33 PM 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.
> > >
> > > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > > ---
> > > 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
Great, for some reason I miss that.
Thanks
>
> 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
> >
>
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