| Message ID | 20240919035214.41805-1-liwenbo.martin@bytedance.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [RESEND,v3] virtio_net: Fix mismatched buf address when unmapping for small packets | expand |
On Thu, 19 Sep 2024 11:52:14 +0800, Wenbo Li <liwenbo.martin@bytedance.com> wrote: > Currently, the virtio-net driver will perform a pre-dma-mapping for > small or mergeable RX buffer. But for small packets, a mismatched address > without VIRTNET_RX_PAD and xdp_headroom is used for unmapping. > > That will result in unsynchronized buffers when SWIOTLB is enabled, for > example, when running as a TDX guest. > > This patch unifies the address passed to the virtio core into the address > of the virtnet header and fixes the mismatched buffer address. > > Changes from v2: unify the buf that passed to the virtio core in small > and merge mode. > Changes from v1: Use ctx to get xdp_headroom. > > Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling mergeable buffers") > Signed-off-by: Wenbo Li <liwenbo.martin@bytedance.com> > Signed-off-by: Jiahui Cen <cenjiahui@bytedance.com> > Signed-off-by: Ying Fang <fangying.tommy@bytedance.com> > --- > drivers/net/virtio_net.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 6f4781ec2b36..9446666c84aa 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -1804,9 +1804,15 @@ static struct sk_buff *receive_small(struct net_device *dev, > struct virtnet_rq_stats *stats) > { > unsigned int xdp_headroom = (unsigned long)ctx; > - struct page *page = virt_to_head_page(buf); > + struct page *page; Because that here is head page, so you can keep the original code. > struct sk_buff *skb; > > + // We passed the address of virtnet header to virtio-core, > + // so truncate the padding. Please check the kernel code style. Thanks. > + buf -= VIRTNET_RX_PAD + xdp_headroom; > + > + page = virt_to_head_page(buf); > + > len -= vi->hdr_len; > u64_stats_add(&stats->bytes, len); > > @@ -2422,8 +2428,9 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq, > if (unlikely(!buf)) > return -ENOMEM; > > - virtnet_rq_init_one_sg(rq, buf + VIRTNET_RX_PAD + xdp_headroom, > - vi->hdr_len + GOOD_PACKET_LEN); > + buf += VIRTNET_RX_PAD + xdp_headroom; > + > + virtnet_rq_init_one_sg(rq, buf, vi->hdr_len + GOOD_PACKET_LEN); > > err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp); > if (err < 0) { > -- > 2.20.1 >
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 6f4781ec2b36..9446666c84aa 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1804,9 +1804,15 @@ static struct sk_buff *receive_small(struct net_device *dev, struct virtnet_rq_stats *stats) { unsigned int xdp_headroom = (unsigned long)ctx; - struct page *page = virt_to_head_page(buf); + struct page *page; struct sk_buff *skb; + // We passed the address of virtnet header to virtio-core, + // so truncate the padding. + buf -= VIRTNET_RX_PAD + xdp_headroom; + + page = virt_to_head_page(buf); + len -= vi->hdr_len; u64_stats_add(&stats->bytes, len); @@ -2422,8 +2428,9 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq, if (unlikely(!buf)) return -ENOMEM; - virtnet_rq_init_one_sg(rq, buf + VIRTNET_RX_PAD + xdp_headroom, - vi->hdr_len + GOOD_PACKET_LEN); + buf += VIRTNET_RX_PAD + xdp_headroom; + + virtnet_rq_init_one_sg(rq, buf, vi->hdr_len + GOOD_PACKET_LEN); err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp); if (err < 0) {
Currently, the virtio-net driver will perform a pre-dma-mapping for small or mergeable RX buffer. But for small packets, a mismatched address without VIRTNET_RX_PAD and xdp_headroom is used for unmapping. That will result in unsynchronized buffers when SWIOTLB is enabled, for example, when running as a TDX guest. This patch unifies the address passed to the virtio core into the address of the virtnet header and fixes the mismatched buffer address. Changes from v2: unify the buf that passed to the virtio core in small and merge mode. Changes from v1: Use ctx to get xdp_headroom. Fixes: 295525e29a5b ("virtio_net: merge dma operations when filling mergeable buffers") Signed-off-by: Wenbo Li <liwenbo.martin@bytedance.com> Signed-off-by: Jiahui Cen <cenjiahui@bytedance.com> Signed-off-by: Ying Fang <fangying.tommy@bytedance.com> --- drivers/net/virtio_net.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)