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[223.218.245.204]) by smtp.googlemail.com with ESMTPSA id p1sm1037307pjr.40.2020.03.30.23.16.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Mar 2020 23:16:27 -0700 (PDT) Subject: Re: [PATCH net v2] veth: xdp: use head instead of hard_start To: Mao Wenan , 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 Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kernel-janitors@vger.kernel.org References: <20200331060641.79999-1-maowenan@huawei.com> From: Toshiaki Makita Message-ID: <7a1d55ad-1427-67fe-f204-4d4a0ab2c4b1@gmail.com> Date: Tue, 31 Mar 2020 15:16:22 +0900 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200331060641.79999-1-maowenan@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2020/03/31 15:06, Mao Wenan wrote: > xdp.data_hard_start is equal to first address of > struct xdp_frame, which is mentioned in > convert_to_xdp_frame(). But the pointer hard_start > in veth_xdp_rcv_one() is 32 bytes offset of frame, > so 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 think you should discuss this more with Jesper before submitting v2. He does not like this to be included now due to merge conflict risk. Basically I agree with him that we don't need to hurry with this fix. Toshiaki Makita > > Fixes: 9fc8d518d9d5 ("veth: Handle xdp_frames in xdp napi ring") > Signed-off-by: Mao Wenan > --- > v2: add fixes tag, as well as commit log. > drivers/net/veth.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/net/veth.c b/drivers/net/veth.c > index d4cbb9e8c63f..5ea550884bf8 100644 > --- a/drivers/net/veth.c > +++ b/drivers/net/veth.c > @@ -506,7 +506,7 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq, > struct xdp_buff xdp; > u32 act; > > - xdp.data_hard_start = hard_start; > + xdp.data_hard_start = head; > xdp.data = frame->data; > xdp.data_end = frame->data + frame->len; > xdp.data_meta = frame->data - frame->metasize; >