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Message-ID: <CACGkMEv5DZgm1B5CXeHnP4ZPmZzQv7zWHT5=D1oH-h_bin2p7w@mail.gmail.com>
Date: Wed, 11 Sep 2024 12:31:32 +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 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?)
> +
> + 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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