| Message ID | 1547724045-2726-8-git-send-email-makita.toshiaki@lab.ntt.co.jp |
|---|---|
| State | Changes Requested |
| Delegated to: | David Miller |
| Headers | show |
| Series | virtio_net: Fix problems around XDP tx and napi_tx | expand |
On 2019/1/17 7:20, Toshiaki Makita wrote: > We do not reset or free up unused buffers when enabling/disabling XDP, > so it can happen that xdp_frames are freed after disabling XDP or > sk_buffs are freed after enabling XDP on xdp tx queues. > Thus we need to handle both forms (xdp_frames and sk_buffs) regardless > of XDP setting. > One way to trigger this problem is to disable XDP when napi_tx is > enabled. In that case, virtnet_xdp_set() calls virtnet_napi_enable() > which kicks NAPI. The NAPI handler will call virtnet_poll_cleantx() > which invokes free_old_xmit_skbs() for queues which have been used by > XDP. > > Note that even with this change we need to keep skipping > free_old_xmit_skbs() from NAPI handlers when XDP is enabled, because XDP > tx queues do not aquire queue locks. > > Fixes: 4941d472bf95 ("virtio-net: do not reset during XDP set") > Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp> > --- > drivers/net/virtio_net.c | 54 +++++++++++++++++++++++++++++++++++++----------- > 1 file changed, 42 insertions(+), 12 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 996de69..6598c25 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -57,6 +57,8 @@ > #define VIRTIO_XDP_TX BIT(0) > #define VIRTIO_XDP_REDIR BIT(1) > > +#define VIRTIO_XDP_FLAG BIT(0) > + > /* RX packet size EWMA. The average packet size is used to determine the packet > * buffer size when refilling RX rings. As the entire RX ring may be refilled > * at once, the weight is chosen so that the EWMA will be insensitive to short- > @@ -252,6 +254,21 @@ struct padded_vnet_hdr { > char padding[4]; > }; > > +static bool is_xdp_frame(void *ptr) > +{ > + return (unsigned long)ptr & VIRTIO_XDP_FLAG; > +} > + > +static void *xdp_to_ptr(struct xdp_frame *ptr) > +{ > + return (void *)((unsigned long)ptr | VIRTIO_XDP_FLAG); > +} > + > +static struct xdp_frame *ptr_to_xdp(void *ptr) > +{ > + return (struct xdp_frame *)((unsigned long)ptr & ~VIRTIO_XDP_FLAG); > +} > + > /* 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 > */ > @@ -462,7 +479,8 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi, > > sg_init_one(sq->sg, xdpf->data, xdpf->len); > > - err = virtqueue_add_outbuf(sq->vq, sq->sg, 1, xdpf, GFP_ATOMIC); > + err = virtqueue_add_outbuf(sq->vq, sq->sg, 1, xdp_to_ptr(xdpf), > + GFP_ATOMIC); > if (unlikely(err)) > return -ENOSPC; /* Caller handle free/refcnt */ > > @@ -482,13 +500,13 @@ static int virtnet_xdp_xmit(struct net_device *dev, > { > struct virtnet_info *vi = netdev_priv(dev); > struct receive_queue *rq = vi->rq; > - struct xdp_frame *xdpf_sent; > struct bpf_prog *xdp_prog; > struct send_queue *sq; > unsigned int len; > int drops = 0; > int kicks = 0; > int ret, err; > + void *ptr; > int i; > > /* Only allow ndo_xdp_xmit if XDP is loaded on dev, as this > @@ -507,8 +525,12 @@ static int virtnet_xdp_xmit(struct net_device *dev, > } > > /* Free up any pending old buffers before queueing new ones. */ > - while ((xdpf_sent = virtqueue_get_buf(sq->vq, &len)) != NULL) > - xdp_return_frame(xdpf_sent); > + while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) { > + if (likely(is_xdp_frame(ptr))) > + xdp_return_frame(ptr_to_xdp(ptr)); > + else > + dev_consume_skb_any(ptr); > + } > > for (i = 0; i < n; i++) { > struct xdp_frame *xdpf = frames[i]; > @@ -1329,18 +1351,26 @@ static int virtnet_receive(struct receive_queue *rq, int budget, > > static void free_old_xmit_skbs(struct send_queue *sq) > { > - struct sk_buff *skb; > unsigned int len; > unsigned int packets = 0; > unsigned int bytes = 0; > + void *ptr; > > - while ((skb = virtqueue_get_buf(sq->vq, &len)) != NULL) { > - pr_debug("Sent skb %p\n", skb); > + while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) { > + if (likely(!is_xdp_frame(ptr))) { > + struct sk_buff *skb = ptr; > > - bytes += skb->len; > - packets++; > + pr_debug("Sent skb %p\n", skb); > > - dev_consume_skb_any(skb); > + bytes += skb->len; > + dev_consume_skb_any(skb); > + } else { > + struct xdp_frame *frame = ptr_to_xdp(ptr); > + > + bytes += frame->len; > + xdp_return_frame(frame); > + } > + packets++; > } > > /* Avoid overhead when no packets have been processed > @@ -2665,10 +2695,10 @@ static void free_unused_bufs(struct virtnet_info *vi) > for (i = 0; i < vi->max_queue_pairs; i++) { > struct virtqueue *vq = vi->sq[i].vq; > while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) { > - if (!is_xdp_raw_buffer_queue(vi, i)) > + if (!is_xdp_frame(buf)) > dev_kfree_skb(buf); > else > - xdp_return_frame(buf); > + xdp_return_frame(ptr_to_xdp(buf)); > } > } > Acked-by: Jason Wang <jasowang@redhat.com> Thanks!
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 996de69..6598c25 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -57,6 +57,8 @@ #define VIRTIO_XDP_TX BIT(0) #define VIRTIO_XDP_REDIR BIT(1) +#define VIRTIO_XDP_FLAG BIT(0) + /* RX packet size EWMA. The average packet size is used to determine the packet * buffer size when refilling RX rings. As the entire RX ring may be refilled * at once, the weight is chosen so that the EWMA will be insensitive to short- @@ -252,6 +254,21 @@ struct padded_vnet_hdr { char padding[4]; }; +static bool is_xdp_frame(void *ptr) +{ + return (unsigned long)ptr & VIRTIO_XDP_FLAG; +} + +static void *xdp_to_ptr(struct xdp_frame *ptr) +{ + return (void *)((unsigned long)ptr | VIRTIO_XDP_FLAG); +} + +static struct xdp_frame *ptr_to_xdp(void *ptr) +{ + return (struct xdp_frame *)((unsigned long)ptr & ~VIRTIO_XDP_FLAG); +} + /* 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 */ @@ -462,7 +479,8 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi, sg_init_one(sq->sg, xdpf->data, xdpf->len); - err = virtqueue_add_outbuf(sq->vq, sq->sg, 1, xdpf, GFP_ATOMIC); + err = virtqueue_add_outbuf(sq->vq, sq->sg, 1, xdp_to_ptr(xdpf), + GFP_ATOMIC); if (unlikely(err)) return -ENOSPC; /* Caller handle free/refcnt */ @@ -482,13 +500,13 @@ static int virtnet_xdp_xmit(struct net_device *dev, { struct virtnet_info *vi = netdev_priv(dev); struct receive_queue *rq = vi->rq; - struct xdp_frame *xdpf_sent; struct bpf_prog *xdp_prog; struct send_queue *sq; unsigned int len; int drops = 0; int kicks = 0; int ret, err; + void *ptr; int i; /* Only allow ndo_xdp_xmit if XDP is loaded on dev, as this @@ -507,8 +525,12 @@ static int virtnet_xdp_xmit(struct net_device *dev, } /* Free up any pending old buffers before queueing new ones. */ - while ((xdpf_sent = virtqueue_get_buf(sq->vq, &len)) != NULL) - xdp_return_frame(xdpf_sent); + while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) { + if (likely(is_xdp_frame(ptr))) + xdp_return_frame(ptr_to_xdp(ptr)); + else + dev_consume_skb_any(ptr); + } for (i = 0; i < n; i++) { struct xdp_frame *xdpf = frames[i]; @@ -1329,18 +1351,26 @@ static int virtnet_receive(struct receive_queue *rq, int budget, static void free_old_xmit_skbs(struct send_queue *sq) { - struct sk_buff *skb; unsigned int len; unsigned int packets = 0; unsigned int bytes = 0; + void *ptr; - while ((skb = virtqueue_get_buf(sq->vq, &len)) != NULL) { - pr_debug("Sent skb %p\n", skb); + while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) { + if (likely(!is_xdp_frame(ptr))) { + struct sk_buff *skb = ptr; - bytes += skb->len; - packets++; + pr_debug("Sent skb %p\n", skb); - dev_consume_skb_any(skb); + bytes += skb->len; + dev_consume_skb_any(skb); + } else { + struct xdp_frame *frame = ptr_to_xdp(ptr); + + bytes += frame->len; + xdp_return_frame(frame); + } + packets++; } /* Avoid overhead when no packets have been processed @@ -2665,10 +2695,10 @@ static void free_unused_bufs(struct virtnet_info *vi) for (i = 0; i < vi->max_queue_pairs; i++) { struct virtqueue *vq = vi->sq[i].vq; while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) { - if (!is_xdp_raw_buffer_queue(vi, i)) + if (!is_xdp_frame(buf)) dev_kfree_skb(buf); else - xdp_return_frame(buf); + xdp_return_frame(ptr_to_xdp(buf)); } }
We do not reset or free up unused buffers when enabling/disabling XDP, so it can happen that xdp_frames are freed after disabling XDP or sk_buffs are freed after enabling XDP on xdp tx queues. Thus we need to handle both forms (xdp_frames and sk_buffs) regardless of XDP setting. One way to trigger this problem is to disable XDP when napi_tx is enabled. In that case, virtnet_xdp_set() calls virtnet_napi_enable() which kicks NAPI. The NAPI handler will call virtnet_poll_cleantx() which invokes free_old_xmit_skbs() for queues which have been used by XDP. Note that even with this change we need to keep skipping free_old_xmit_skbs() from NAPI handlers when XDP is enabled, because XDP tx queues do not aquire queue locks. Fixes: 4941d472bf95 ("virtio-net: do not reset during XDP set") Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp> --- drivers/net/virtio_net.c | 54 +++++++++++++++++++++++++++++++++++++----------- 1 file changed, 42 insertions(+), 12 deletions(-)