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Message-ID: <fb4e9ec4-9ad2-ab64-1bca-579727fec8e0@linux.alibaba.com>
Date: Sat, 14 Jan 2023 15:16:15 +0800
From: Heng Qi <hengqi@...ux.alibaba.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org,
Jason Wang <jasowang@...hat.com>,
"Michael S . Tsirkin" <mst@...hat.com>,
Paolo Abeni <pabeni@...hat.com>,
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>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH net-next v4 02/10] virtio-net: fix calculation of MTU for
single buffer xdp
在 2023/1/14 下午2:24, Jakub Kicinski 写道:
> On Fri, 13 Jan 2023 16:00:08 +0800 Heng Qi wrote:
>> When single-buffer xdp is loaded, the size of the buffer filled each time
>> is 'sz = (PAGE_SIZE - headroom - tailroom)', which is the maximum packet
>> length that the driver allows the device to pass in. Otherwise, the packet
>> with a length greater than sz will come in, so num_buf will be greater than
>> or equal to 2, and then xdp_linearize_page() will be performed and the
>> packet will be dropped because the total length is greater than PAGE_SIZE.
>> So the maximum value of MTU for single-buffer xdp is 'max_sz = sz - ETH_HLEN'.
> drivers/net/virtio_net.c:3111:56: warning: format specifies type 'unsigned long' but the argument has type 'unsigned int' [-Wformat]
> netdev_warn(dev, "XDP requires MTU less than %lu\n", max_sz);
> ~~~ ^~~~~~
> %u
The corresponding netdev_warn are split into [PATCH net-next v4 03/10],
and I will reorganize the patches [PATCH net-next v4 02/10] and [PATCH
net-next v4 03/10] to be more independent.
Thanks.
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