From: Toshiaki Makita <toshiaki.makita1@gmail.com>
To: Jesper Dangaard Brouer <jbrouer@redhat.com>,
Mao Wenan <maowenan@huawei.com>
Cc: davem@davemloft.net, ast@kernel.org, daniel@iogearbox.net,
kuba@kernel.org, hawk@kernel.org, john.fastabend@gmail.com,
kafai@fb.com, songliubraving@fb.com, yhs@fb.com, andriin@fb.com,
jwi@linux.ibm.com, jianglidong3@jd.com, edumazet@google.com,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
bpf@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH net] veth: xdp: use head instead of hard_start
Date: Tue, 31 Mar 2020 08:35:39 +0900 [thread overview]
Message-ID: <3053de4c-cee6-f6fc-efc2-09c6250f3ef2@gmail.com> (raw)
In-Reply-To: <20200330133442.132bde0c@carbon>
Hi Mao & Jesper
(Resending with plain text...)
On 2020/03/30 20:34, Jesper Dangaard Brouer wrote:
> On Mon, 30 Mar 2020 18:26:31 +0800
> Mao Wenan <maowenan@huawei.com> wrote:
>
>> xdp.data_hard_start is mapped to the first
>> address of xdp_frame, but the pointer hard_start
>> is the offset(sizeof(struct xdp_frame)) of xdp_frame,
>> it should use head instead of hard_start to
>> set xdp.data_hard_start. Otherwise, if BPF program
>> calls helper_function such as bpf_xdp_adjust_head, it
>> will be confused for xdp_frame_end.
>
> I have noticed this[1] and have a patch in my current patchset for
> fixing this. IMHO is is not so important fix right now, as the effect
> is that you currently only lose 32 bytes of headroom.
>
> [1] https://lore.kernel.org/netdev/158446621887.702578.17234304084556809684.stgit@firesoul/
You are right, the subtraction is not necessary here.
Thank you for working on this.
Toshiaki Makita
next prev parent reply other threads:[~2020-03-30 23:35 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-30 10:26 [PATCH net] veth: xdp: use head instead of hard_start Mao Wenan
2020-03-30 11:34 ` Jesper Dangaard Brouer
2020-03-30 23:35 ` Toshiaki Makita [this message]
2020-03-31 3:56 ` maowenan
2020-03-31 5:45 ` Toshiaki Makita
2020-03-31 6:06 ` [PATCH net v2] " Mao Wenan
2020-03-31 6:16 ` Toshiaki Makita
2020-04-01 16:15 ` Jesper Dangaard Brouer
2020-04-02 0:47 ` Toshiaki Makita
2020-04-02 9:06 ` Jesper Dangaard Brouer
2020-04-02 15:40 ` Alexei Starovoitov
2020-04-03 7:58 ` Jesper Dangaard Brouer
2020-04-03 21:12 ` Alexei Starovoitov
2020-04-02 1:23 ` maowenan
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