netdev - [RFC PATCH 1/9] virtio_net: disable the hole mechanism for xdp

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Message-Id: <20221122074348.88601-2-hengqi@linux.alibaba.com>
Date:   Tue, 22 Nov 2022 15:43:40 +0800
From:   Heng Qi <hengqi@...ux.alibaba.com>
To:     netdev@...r.kernel.org, bpf@...r.kernel.org
Cc:     Jason Wang <jasowang@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>
Subject: [RFC PATCH 1/9] virtio_net: disable the hole mechanism for xdp

XDP core assumes that the frame_size of xdp_buff and the length of
the frag are PAGE_SIZE. But before xdp is set, the length of the prefilled
buffer may exceed PAGE_SIZE, which may cause the processing of xdp to fail,
so we disable the hole mechanism when xdp is loaded.

Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
---
 drivers/net/virtio_net.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 9cce7dec7366..c5046d21b281 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1419,8 +1419,11 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
 		/* To avoid internal fragmentation, if there is very likely not
 		 * enough space for another buffer, add the remaining space to
 		 * the current buffer.
+		 * XDP core assumes that frame_size of xdp_buff and the length
+		 * of the frag are PAGE_SIZE, so we disable the hole mechanism.
 		 */
-		len += hole;
+		if (!vi->xdp_enabled)
+			len += hole;
 		alloc_frag->offset += hole;
 	}
 
-- 
2.19.1.6.gb485710b