1. Patchew
  2. linux
  3. View series

[PATCH v2] virtio_net: Fix mismatched buf address when unmapping for small packets

Wenbo Li posted 1 patch 1 year, 5 months ago
There is a newer version of this series
drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)
[PATCH v2] virtio_net: Fix mismatched buf address when unmapping for small packets
Posted by Wenbo Li 1 year, 5 months ago 
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 handles small and mergeable packets separately and fixes
the mismatched buffer address.

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 | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index c6af18948..cbc3c0ae4 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -891,6 +891,23 @@ static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
 	return buf;
 }
 
+static void *virtnet_rq_get_buf_small(struct receive_queue *rq,
+				      u32 *len,
+				      void **ctx,
+				      unsigned int header_offset)
+{
+	void *buf;
+	unsigned int xdp_headroom;
+
+	buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
+	if (buf) {
+		xdp_headroom = (unsigned long)*ctx;
+		virtnet_rq_unmap(rq, buf + VIRTNET_RX_PAD + xdp_headroom, *len);
+	}
+
+	return buf;
+}
+
 static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
 {
 	struct virtnet_rq_dma *dma;
@@ -2692,13 +2709,23 @@ static int virtnet_receive_packets(struct virtnet_info *vi,
 	int packets = 0;
 	void *buf;
 
-	if (!vi->big_packets || vi->mergeable_rx_bufs) {
+	if (vi->mergeable_rx_bufs) {
 		void *ctx;
 		while (packets < budget &&
 		       (buf = virtnet_rq_get_buf(rq, &len, &ctx))) {
 			receive_buf(vi, rq, buf, len, ctx, xdp_xmit, stats);
 			packets++;
 		}
+	} else if (!vi->big_packets) {
+		void *ctx;
+		unsigned int xdp_headroom = virtnet_get_headroom(vi);
+		unsigned int header_offset = VIRTNET_RX_PAD + xdp_headroom;
+
+		while (packets < budget &&
+		       (buf = virtnet_rq_get_buf_small(rq, &len, &ctx, header_offset))) {
+			receive_buf(vi, rq, buf, len, ctx, xdp_xmit, stats);
+			packets++;
+		}
 	} else {
 		while (packets < budget &&
 		       (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
-- 
2.20.1
Re: [PATCH v2] virtio_net: Fix mismatched buf address when unmapping for small packets
Posted by Xuan Zhuo 1 year, 5 months ago 
On Wed,  4 Sep 2024 14:10:09 +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.

Will used virt_to_head_page(), so could you say more about it?

	struct page *page = virt_to_head_page(buf);

Thanks.

>
> That will result in unsynchronized buffers when SWIOTLB is enabled, for
> example, when running as a TDX guest.
>
> This patch handles small and mergeable packets separately and fixes
> the mismatched buffer address.
>
> 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 | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index c6af18948..cbc3c0ae4 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -891,6 +891,23 @@ static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
>  	return buf;
>  }
>
> +static void *virtnet_rq_get_buf_small(struct receive_queue *rq,
> +				      u32 *len,
> +				      void **ctx,
> +				      unsigned int header_offset)
> +{
> +	void *buf;
> +	unsigned int xdp_headroom;
> +
> +	buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
> +	if (buf) {
> +		xdp_headroom = (unsigned long)*ctx;
> +		virtnet_rq_unmap(rq, buf + VIRTNET_RX_PAD + xdp_headroom, *len);
> +	}
> +
> +	return buf;
> +}
> +
>  static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
>  {
>  	struct virtnet_rq_dma *dma;
> @@ -2692,13 +2709,23 @@ static int virtnet_receive_packets(struct virtnet_info *vi,
>  	int packets = 0;
>  	void *buf;
>
> -	if (!vi->big_packets || vi->mergeable_rx_bufs) {
> +	if (vi->mergeable_rx_bufs) {
>  		void *ctx;
>  		while (packets < budget &&
>  		       (buf = virtnet_rq_get_buf(rq, &len, &ctx))) {
>  			receive_buf(vi, rq, buf, len, ctx, xdp_xmit, stats);
>  			packets++;
>  		}
> +	} else if (!vi->big_packets) {
> +		void *ctx;
> +		unsigned int xdp_headroom = virtnet_get_headroom(vi);
> +		unsigned int header_offset = VIRTNET_RX_PAD + xdp_headroom;
> +
> +		while (packets < budget &&
> +		       (buf = virtnet_rq_get_buf_small(rq, &len, &ctx, header_offset))) {
> +			receive_buf(vi, rq, buf, len, ctx, xdp_xmit, stats);
> +			packets++;
> +		}
>  	} else {
>  		while (packets < budget &&
>  		       (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
> --
> 2.20.1
>
Re: [PATCH v2] virtio_net: Fix mismatched buf address when unmapping for small packets
Posted by Jason Wang 1 year, 5 months ago 
On Wed, Sep 4, 2024 at 2:10 PM 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 handles small and mergeable packets separately and fixes
> the mismatched buffer address.
>
> 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 | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index c6af18948..cbc3c0ae4 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -891,6 +891,23 @@ static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
>         return buf;
>  }
>
> +static void *virtnet_rq_get_buf_small(struct receive_queue *rq,
> +                                     u32 *len,
> +                                     void **ctx,
> +                                     unsigned int header_offset)

header_offset is unused?

> +{
> +       void *buf;
> +       unsigned int xdp_headroom;
> +
> +       buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
> +       if (buf) {
> +               xdp_headroom = (unsigned long)*ctx;
> +               virtnet_rq_unmap(rq, buf + VIRTNET_RX_PAD + xdp_headroom, *len);
> +       }
> +
> +       return buf;
> +}
> +
>  static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
>  {
>         struct virtnet_rq_dma *dma;
> @@ -2692,13 +2709,23 @@ static int virtnet_receive_packets(struct virtnet_info *vi,
>         int packets = 0;
>         void *buf;
>
> -       if (!vi->big_packets || vi->mergeable_rx_bufs) {
> +       if (vi->mergeable_rx_bufs) {
>                 void *ctx;
>                 while (packets < budget &&
>                        (buf = virtnet_rq_get_buf(rq, &len, &ctx))) {
>                         receive_buf(vi, rq, buf, len, ctx, xdp_xmit, stats);
>                         packets++;
>                 }
> +       } else if (!vi->big_packets) {
> +               void *ctx;
> +               unsigned int xdp_headroom = virtnet_get_headroom(vi);
> +               unsigned int header_offset = VIRTNET_RX_PAD + xdp_headroom;
> +
> +               while (packets < budget &&
> +                      (buf = virtnet_rq_get_buf_small(rq, &len, &ctx, header_offset))) {
> +                       receive_buf(vi, rq, buf, len, ctx, xdp_xmit, stats);
> +                       packets++;
> +               }
>         } else {
>                 while (packets < budget &&
>                        (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
> --
> 2.20.1
>

Thanks

Patchew 2.1-devel-b67e4c2

© 2016 - 2026 Red Hat, Inc.