Re: [PATCH bpf-next v3 1/3] net: add priv_flags for allow tx skb without linear

From: Alexander Lobakin <alobakin@pm.me>
To: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: "Alexander Lobakin" <alobakin@pm.me>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	"Jason Wang" <jasowang@redhat.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Björn Töpel" <bjorn@kernel.org>,
	"Magnus Karlsson" <magnus.karlsson@intel.com>,
	"Jonathan Lemon" <jonathan.lemon@gmail.com>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Jesper Dangaard Brouer" <hawk@kernel.org>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"Andrii Nakryiko" <andrii@kernel.org>,
	"Martin KaFai Lau" <kafai@fb.com>,
	"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
	"KP Singh" <kpsingh@kernel.org>,
	virtualization@lists.linux-foundation.org, bpf@vger.kernel.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf-next v3 1/3] net: add priv_flags for allow tx skb without linear
Date: Thu, 21 Jan 2021 15:13:39 +0000	[thread overview]
Message-ID: <20210121151320.3018-1-alobakin@pm.me> (raw)
In-Reply-To: <d44e0c054675e816b1ece745be795bd2a8b88350.1611236588.git.xuanzhuo@linux.alibaba.com>

From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Date: Thu, 21 Jan 2021 21:47:07 +0800

> 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.
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> Suggested-by: Alexander Lobakin <alobakin@pm.me>

Acked-by: Alexander Lobakin <alobakin@pm.me>

> ---
>  include/linux/netdevice.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index ef51725..135db8f 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1525,6 +1525,7 @@ struct net_device_ops {
>   * @IFF_FAILOVER_SLAVE: device is lower dev of a failover master device
>   * @IFF_L3MDEV_RX_HANDLER: only invoke the rx handler of L3 master device
>   * @IFF_LIVE_RENAME_OK: rename is allowed while device is up and running
> + * @IFF_TX_SKB_NO_LINEAR: allow tx skb linear is empty
>   */
>  enum netdev_priv_flags {
>  	IFF_802_1Q_VLAN			= 1<<0,
> @@ -1558,6 +1559,7 @@ enum netdev_priv_flags {
>  	IFF_FAILOVER_SLAVE		= 1<<28,
>  	IFF_L3MDEV_RX_HANDLER		= 1<<29,
>  	IFF_LIVE_RENAME_OK		= 1<<30,
> +	IFF_TX_SKB_NO_LINEAR		= 1<<31,
>  };
>  
>  #define IFF_802_1Q_VLAN			IFF_802_1Q_VLAN
> @@ -1590,6 +1592,7 @@ enum netdev_priv_flags {
>  #define IFF_FAILOVER_SLAVE		IFF_FAILOVER_SLAVE
>  #define IFF_L3MDEV_RX_HANDLER		IFF_L3MDEV_RX_HANDLER
>  #define IFF_LIVE_RENAME_OK		IFF_LIVE_RENAME_OK
> +#define IFF_TX_SKB_NO_LINEAR		IFF_TX_SKB_NO_LINEAR
>  
>  /**
>   *	struct net_device - The DEVICE structure.
> -- 
> 1.8.3.1

Thanks,
Al