Re: [PATCH v2] virtio_net: Fix mismatched buf address when unmapping for small packets
From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Date: 2024-09-04 06:46:21
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lkml, virtualization
On Wed, 4 Sep 2024 14:10:09 +0800, Wenbo Li [off-list ref] 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.
quoted hunk ↗ jump to hunk
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 <redacted> Signed-off-by: Jiahui Cen <redacted> Signed-off-by: Ying Fang <redacted> --- 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