netdev - Re: [PATCH bpf-next v2 1/3] net: add priv_flags for allow tx skb without linear

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Date:   Wed, 20 Jan 2021 11:01:24 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, netdev@...r.kernel.org
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Björn Töpel <bjorn.topel@...el.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 1/3] net: add priv_flags for allow tx skb
 without linear


On 2021/1/19 下午5:45, Xuan Zhuo wrote:
> In some cases, we hope to construct skb directly based on the existing
> memory without copying data. In this case, the page will be placed
> directly in the skb, and the linear space of skb is empty. But
> unfortunately, many the network card does not support this operation.
> For example Mellanox Technologies MT27710 Family [ConnectX-4 Lx] will
> get the following error message:
>
>      mlx5_core 0000:3b:00.1 eth1: Error cqe on cqn 0x817, ci 0x8, qn 0x1dbb, opcode 0xd, syndrome 0x1, vendor syndrome 0x68
>      00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>      00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>      00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>      00000030: 00 00 00 00 60 10 68 01 0a 00 1d bb 00 0f 9f d2
>      WQE DUMP: WQ size 1024 WQ cur size 0, WQE index 0xf, len: 64
>      00000000: 00 00 0f 0a 00 1d bb 03 00 00 00 08 00 00 00 00
>      00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>      00000020: 00 00 00 2b 00 08 00 00 00 00 00 05 9e e3 08 00
>      00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>      mlx5_core 0000:3b:00.1 eth1: ERR CQE on SQ: 0x1dbb
>
> So a priv_flag is added here to indicate whether the network card
> supports this feature.


I don't see Mellanox engineers are copied. I wonder if we need their 
confirmation on whether it's a bug or hardware limitation.

Thanks