From: Toshiaki Makita <toshiaki.makita1@gmail.com>
To: maowenan <maowenan@huawei.com>,
Jesper Dangaard Brouer <jbrouer@redhat.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 14:45:26 +0900 [thread overview]
Message-ID: <fb5ab568-9bc8-3145-a8db-3e975ccdf846@gmail.com> (raw)
In-Reply-To: <e7cf1271-2953-a5aa-ab25-c4b4a3843ee1@huawei.com>
On 2020/03/31 12:56, maowenan wrote:
> On 2020/3/31 7:35, Toshiaki Makita wrote:
>> 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.
>>>
> I consider that it is needed because bpf_xdp_adjust_head() just a common helper function,
> veth as one driver application should keep the same as 32 bytes of headroom as other driver.
> And convert_to_xdp_frame set() also store info in top of packet, and set:
> xdp_frame = xdp->data_hard_start;
>
>>> [1] https://lore.kernel.org/netdev/158446621887.702578.17234304084556809684.stgit@firesoul/
>>
>> You are right, the subtraction is not necessary here.
> I guess you mean that previous subtraction is not necessary ? this line : void *head = hard_start - sizeof(struct xdp_frame); ?
No I just mean subtraction of headroom is not necessary, and I noticed this
description was confusing. Sorry about that.
You can use "head" for data_hard_start.
Toshiaki Makita
next prev parent reply other threads:[~2020-03-31 5:45 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
2020-03-31 3:56 ` maowenan
2020-03-31 5:45 ` Toshiaki Makita [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=fb5ab568-9bc8-3145-a8db-3e975ccdf846@gmail.com \
--to=toshiaki.makita1@gmail.com \
--cc=andriin@fb.com \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=hawk@kernel.org \
--cc=jbrouer@redhat.com \
--cc=jianglidong3@jd.com \
--cc=john.fastabend@gmail.com \
--cc=jwi@linux.ibm.com \
--cc=kafai@fb.com \
--cc=kernel-janitors@vger.kernel.org \
--cc=kuba@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=maowenan@huawei.com \
--cc=netdev@vger.kernel.org \
--cc=songliubraving@fb.com \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).