| Message ID | 20161202205122.4331.70274.stgit@john-Precision-Tower-5810 |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
On 16-12-02 12:51 PM, John Fastabend wrote: > This adds support for the XDP_TX action to virtio_net. When an XDP > program is run and returns the XDP_TX action the virtio_net XDP > implementation will transmit the packet on a TX queue that aligns > with the current CPU that the XDP packet was processed on. > > Before sending the packet the header is zeroed. Also XDP is expected > to handle checksum correctly so no checksum offload support is > provided. > > Signed-off-by: John Fastabend <john.r.fastabend@intel.com> > --- > drivers/net/virtio_net.c | 63 ++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 60 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index b67203e..137caba 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -330,12 +330,43 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, > return skb; > } > > +static void virtnet_xdp_xmit(struct virtnet_info *vi, > + unsigned int qnum, struct xdp_buff *xdp) > +{ > + struct send_queue *sq = &vi->sq[qnum]; > + struct virtio_net_hdr_mrg_rxbuf *hdr; > + unsigned int num_sg, len; > + void *xdp_sent; > + int err; > + > + /* Free up any pending old buffers before queueing new ones. */ > + while ((xdp_sent = virtqueue_get_buf(sq->vq, &len)) != NULL) { > + struct page *page = virt_to_head_page(xdp_sent); > + > + put_page(page); > + } > + > + /* Zero header and leave csum up to XDP layers */ > + hdr = xdp->data; > + memset(hdr, 0, vi->hdr_len); > + > + num_sg = 1; > + sg_init_one(sq->sg, xdp->data, xdp->data_end - xdp->data); > + err = virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, > + xdp->data, GFP_ATOMIC); > + if (unlikely(err)) > + put_page(virt_to_head_page(xdp->data)); > + else > + virtqueue_kick(sq->vq); > +} > + Hi Michael, Any idea why the above pattern > + err = virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, > + xdp->data, GFP_ATOMIC); > + if (unlikely(err)) > + put_page(virt_to_head_page(xdp->data)); > + else > + virtqueue_kick(sq->vq); > +} would cause a hang but if I call the virtqueue_kick as below even in the error case everything seems to be fine. err = virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, xdp->data, GFP_ATOMIC); if (unlikely(err)) put_page(virt_to_head_page(xdp->data)); virtqueue_kick(sq->vq); I'll take a look through the virtio code but thought I might ask in case you know off-hand or it could be something else entirely. I noticed virtio_input.c uses the second pattern and virtio_net.c uses the above pattern but I'm guessing it never gets exercised due to stack backoff. Thanks, John
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index b67203e..137caba 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -330,12 +330,43 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, return skb; } +static void virtnet_xdp_xmit(struct virtnet_info *vi, + unsigned int qnum, struct xdp_buff *xdp) +{ + struct send_queue *sq = &vi->sq[qnum]; + struct virtio_net_hdr_mrg_rxbuf *hdr; + unsigned int num_sg, len; + void *xdp_sent; + int err; + + /* Free up any pending old buffers before queueing new ones. */ + while ((xdp_sent = virtqueue_get_buf(sq->vq, &len)) != NULL) { + struct page *page = virt_to_head_page(xdp_sent); + + put_page(page); + } + + /* Zero header and leave csum up to XDP layers */ + hdr = xdp->data; + memset(hdr, 0, vi->hdr_len); + + num_sg = 1; + sg_init_one(sq->sg, xdp->data, xdp->data_end - xdp->data); + err = virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, + xdp->data, GFP_ATOMIC); + if (unlikely(err)) + put_page(virt_to_head_page(xdp->data)); + else + virtqueue_kick(sq->vq); +} + static u32 do_xdp_prog(struct virtnet_info *vi, struct bpf_prog *xdp_prog, struct page *page, int offset, int len) { int hdr_padded_len; struct xdp_buff xdp; + unsigned int qp; u32 act; u8 *buf; @@ -353,9 +384,15 @@ static u32 do_xdp_prog(struct virtnet_info *vi, switch (act) { case XDP_PASS: return XDP_PASS; + case XDP_TX: + qp = vi->curr_queue_pairs - + vi->xdp_queue_pairs + + smp_processor_id(); + xdp.data = buf + (vi->mergeable_rx_bufs ? 0 : 4); + virtnet_xdp_xmit(vi, qp, &xdp); + return XDP_TX; default: bpf_warn_invalid_xdp_action(act); - case XDP_TX: case XDP_ABORTED: case XDP_DROP: return XDP_DROP; @@ -391,8 +428,16 @@ static struct sk_buff *receive_big(struct net_device *dev, if (unlikely(hdr->hdr.gso_type || hdr->hdr.flags)) goto err_xdp; act = do_xdp_prog(vi, xdp_prog, page, 0, len); - if (act == XDP_DROP) + switch (act) { + case XDP_PASS: + break; + case XDP_TX: + rcu_read_unlock(); + goto xdp_xmit; + case XDP_DROP: + default: goto err_xdp; + } } rcu_read_unlock(); @@ -407,6 +452,7 @@ static struct sk_buff *receive_big(struct net_device *dev, err: dev->stats.rx_dropped++; give_pages(rq, page); +xdp_xmit: return NULL; } @@ -425,6 +471,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, struct bpf_prog *xdp_prog; unsigned int truesize; + head_skb = NULL; + rcu_read_lock(); xdp_prog = rcu_dereference(rq->xdp_prog); if (xdp_prog) { @@ -449,8 +497,16 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, goto err_xdp; act = do_xdp_prog(vi, xdp_prog, page, offset, len); - if (act == XDP_DROP) + switch (act) { + case XDP_PASS: + break; + case XDP_TX: + rcu_read_unlock(); + goto xdp_xmit; + case XDP_DROP: + default: goto err_xdp; + } } rcu_read_unlock(); @@ -528,6 +584,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, err_buf: dev->stats.rx_dropped++; dev_kfree_skb(head_skb); +xdp_xmit: return NULL; }
This adds support for the XDP_TX action to virtio_net. When an XDP program is run and returns the XDP_TX action the virtio_net XDP implementation will transmit the packet on a TX queue that aligns with the current CPU that the XDP packet was processed on. Before sending the packet the header is zeroed. Also XDP is expected to handle checksum correctly so no checksum offload support is provided. Signed-off-by: John Fastabend <john.r.fastabend@intel.com> --- drivers/net/virtio_net.c | 63 ++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 60 insertions(+), 3 deletions(-)