On Wed, 4 Sep 2024 14:10:09 +0800, Wenbo Li <liwenbo.martin@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> Signed-off-by: Jiahui Cen <cenjiahui@xxxxxxxxxxxxx>
> Signed-off-by: Ying Fang <fangying.tommy@xxxxxxxxxxxxx>
> ---
> 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
>
