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Date: Thu, 14 Jan 2021 16:57:32 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Boris Pismenny <borisp@...lanox.com>
Cc: Jakub Kicinski <kuba@...nel.org>,
David Miller <davem@...emloft.net>,
Saeed Mahameed <saeedm@...dia.com>,
Christoph Hellwig <hch@....de>, sagi@...mberg.me, axboe@...com,
kbusch@...nel.org, Al Viro <viro@...iv.linux.org.uk>,
David Ahern <dsahern@...il.com>, smalin@...vell.com,
boris.pismenny@...il.com, linux-nvme@...ts.infradead.org,
netdev <netdev@...r.kernel.org>, benishay@...dia.com,
ogerlitz@...dia.com, yorayz@...dia.com,
Ben Ben-Ishay <benishay@...lanox.com>,
Or Gerlitz <ogerlitz@...lanox.com>,
Yoray Zack <yorayz@...lanox.com>
Subject: Re: [PATCH v2 net-next 02/21] net: Introduce direct data placement
tcp offload
On Thu, Jan 14, 2021 at 4:10 PM Boris Pismenny <borisp@...lanox.com> wrote:
>
> This commit introduces direct data placement offload for TCP.
> This capability is accompanied by new net_device operations that
> configure hardware contexts. There is a context per socket, and a context per DDP
> opreation. Additionally, a resynchronization routine is used to assist
> hardware handle TCP OOO, and continue the offload.
> Furthermore, we let the offloading driver advertise what is the max hw
> sectors/segments.
>
> Using this interface, the NIC hardware will scatter TCP payload directly
> to the BIO pages according to the command_id.
> To maintain the correctness of the network stack, the driver is expected
> to construct SKBs that point to the BIO pages.
>
> This, the SKB represents the data on the wire, while it is pointing
> to data that is already placed in the destination buffer.
> As a result, data from page frags should not be copied out to
> the linear part.
>
> As SKBs that use DDP are already very memory efficient, we modify
> skb_condence to avoid copying data from fragments to the linear
> part of SKBs that belong to a socket that uses DDP offload.
>
> A follow-up patch will use this interface for DDP in NVMe-TCP.
>
> Signed-off-by: Boris Pismenny <borisp@...lanox.com>
> Signed-off-by: Ben Ben-Ishay <benishay@...lanox.com>
> Signed-off-by: Or Gerlitz <ogerlitz@...lanox.com>
> Signed-off-by: Yoray Zack <yorayz@...lanox.com>
> ---
> include/linux/netdev_features.h | 2 +
> include/linux/netdevice.h | 5 ++
> include/net/inet_connection_sock.h | 4 +
> include/net/tcp_ddp.h | 136 +++++++++++++++++++++++++++++
> net/Kconfig | 9 ++
> net/core/skbuff.c | 9 +-
> net/ethtool/common.c | 1 +
> 7 files changed, 165 insertions(+), 1 deletion(-)
> create mode 100644 include/net/tcp_ddp.h
>
> diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
> index 934de56644e7..fb35dcac03d2 100644
> --- a/include/linux/netdev_features.h
> +++ b/include/linux/netdev_features.h
> @@ -84,6 +84,7 @@ enum {
> NETIF_F_GRO_FRAGLIST_BIT, /* Fraglist GRO */
>
> NETIF_F_HW_MACSEC_BIT, /* Offload MACsec operations */
> + NETIF_F_HW_TCP_DDP_BIT, /* TCP direct data placement offload */
>
> /*
> * Add your fresh new feature above and remember to update
> @@ -157,6 +158,7 @@ enum {
> #define NETIF_F_GRO_FRAGLIST __NETIF_F(GRO_FRAGLIST)
> #define NETIF_F_GSO_FRAGLIST __NETIF_F(GSO_FRAGLIST)
> #define NETIF_F_HW_MACSEC __NETIF_F(HW_MACSEC)
> +#define NETIF_F_HW_TCP_DDP __NETIF_F(HW_TCP_DDP)
>
> /* Finds the next feature with the highest number of the range of start till 0.
> */
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 259be67644e3..3dd3cdf5dec3 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -941,6 +941,7 @@ struct dev_ifalias {
>
> struct devlink;
> struct tlsdev_ops;
> +struct tcp_ddp_dev_ops;
>
> struct netdev_name_node {
> struct hlist_node hlist;
> @@ -1937,6 +1938,10 @@ struct net_device {
> const struct tlsdev_ops *tlsdev_ops;
> #endif
>
> +#ifdef CONFIG_TCP_DDP
> + const struct tcp_ddp_dev_ops *tcp_ddp_ops;
> +#endif
> +
> const struct header_ops *header_ops;
>
> unsigned int flags;
> diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
> index 7338b3865a2a..a08b85b53aa8 100644
> --- a/include/net/inet_connection_sock.h
> +++ b/include/net/inet_connection_sock.h
> @@ -66,6 +66,8 @@ struct inet_connection_sock_af_ops {
> * @icsk_ulp_ops Pluggable ULP control hook
> * @icsk_ulp_data ULP private data
> * @icsk_clean_acked Clean acked data hook
> + * @icsk_ulp_ddp_ops Pluggable ULP direct data placement control hook
> + * @icsk_ulp_ddp_data ULP direct data placement private data
> * @icsk_listen_portaddr_node hash to the portaddr listener hashtable
> * @icsk_ca_state: Congestion control state
> * @icsk_retransmits: Number of unrecovered [RTO] timeouts
> @@ -94,6 +96,8 @@ struct inet_connection_sock {
> const struct tcp_ulp_ops *icsk_ulp_ops;
> void __rcu *icsk_ulp_data;
> void (*icsk_clean_acked)(struct sock *sk, u32 acked_seq);
#ifdef CONFIG_TCP_DDP ?
> + const struct tcp_ddp_ulp_ops *icsk_ulp_ddp_ops;
> + void __rcu *icsk_ulp_ddp_data;
> struct hlist_node icsk_listen_portaddr_node;
> unsigned int (*icsk_sync_mss)(struct sock *sk, u32 pmtu);
> __u8 icsk_ca_state:5,
> diff --git a/include/net/tcp_ddp.h b/include/net/tcp_ddp.h
> new file mode 100644
> index 000000000000..31e5b1a16d0f
> --- /dev/null
> +++ b/include/net/tcp_ddp.h
> @@ -0,0 +1,136 @@
> +/* SPDX-License-Identifier: GPL-2.0
> + *
> + * tcp_ddp.h
> + * Author: Boris Pismenny <borisp@...lanox.com>
> + * Copyright (C) 2021 Mellanox Technologies.
> + */
> +#ifndef _TCP_DDP_H
> +#define _TCP_DDP_H
> +
> +#include <linux/netdevice.h>
> +#include <net/inet_connection_sock.h>
> +#include <net/sock.h>
> +
> +/* limits returned by the offload driver, zero means don't care */
> +struct tcp_ddp_limits {
> + int max_ddp_sgl_len;
> +};
> +
> +enum tcp_ddp_type {
> + TCP_DDP_NVME = 1,
> +};
> +
> +/**
> + * struct tcp_ddp_config - Generic tcp ddp configuration: tcp ddp IO queue
> + * config implementations must use this as the first member.
> + * Add new instances of tcp_ddp_config below (nvme-tcp, etc.).
> + */
> +struct tcp_ddp_config {
> + enum tcp_ddp_type type;
> + unsigned char buf[];
> +};
> +
> +/**
> + * struct nvme_tcp_ddp_config - nvme tcp ddp configuration for an IO queue
> + *
> + * @pfv: pdu version (e.g., NVME_TCP_PFV_1_0)
> + * @cpda: controller pdu data alignmend (dwords, 0's based)
> + * @dgst: digest types enabled.
> + * The netdev will offload crc if ddp_crc is supported.
> + * @queue_size: number of nvme-tcp IO queue elements
> + * @queue_id: queue identifier
> + * @cpu_io: cpu core running the IO thread for this queue
> + */
> +struct nvme_tcp_ddp_config {
> + struct tcp_ddp_config cfg;
> +
> + u16 pfv;
> + u8 cpda;
> + u8 dgst;
> + int queue_size;
> + int queue_id;
> + int io_cpu;
> +};
> +
> +/**
> + * struct tcp_ddp_io - tcp ddp configuration for an IO request.
> + *
> + * @command_id: identifier on the wire associated with these buffers
> + * @nents: number of entries in the sg_table
> + * @sg_table: describing the buffers for this IO request
> + * @first_sgl: first SGL in sg_table
> + */
> +struct tcp_ddp_io {
> + u32 command_id;
> + int nents;
> + struct sg_table sg_table;
> + struct scatterlist first_sgl[SG_CHUNK_SIZE];
> +};
> +
> +/* struct tcp_ddp_dev_ops - operations used by an upper layer protocol to configure ddp offload
> + *
> + * @tcp_ddp_limits: limit the number of scatter gather entries per IO.
> + * the device driver can use this to limit the resources allocated per queue.
> + * @tcp_ddp_sk_add: add offload for the queue represennted by the socket+config pair.
> + * this function is used to configure either copy, crc or both offloads.
> + * @tcp_ddp_sk_del: remove offload from the socket, and release any device related resources.
> + * @tcp_ddp_setup: request copy offload for buffers associated with a command_id in tcp_ddp_io.
> + * @tcp_ddp_teardown: release offload resources association between buffers and command_id in
> + * tcp_ddp_io.
> + * @tcp_ddp_resync: respond to the driver's resync_request. Called only if resync is successful.
> + */
> +struct tcp_ddp_dev_ops {
> + int (*tcp_ddp_limits)(struct net_device *netdev,
> + struct tcp_ddp_limits *limits);
> + int (*tcp_ddp_sk_add)(struct net_device *netdev,
> + struct sock *sk,
> + struct tcp_ddp_config *config);
> + void (*tcp_ddp_sk_del)(struct net_device *netdev,
> + struct sock *sk);
> + int (*tcp_ddp_setup)(struct net_device *netdev,
> + struct sock *sk,
> + struct tcp_ddp_io *io);
> + int (*tcp_ddp_teardown)(struct net_device *netdev,
> + struct sock *sk,
> + struct tcp_ddp_io *io,
> + void *ddp_ctx);
> + void (*tcp_ddp_resync)(struct net_device *netdev,
> + struct sock *sk, u32 seq);
> +};
> +
> +#define TCP_DDP_RESYNC_REQ BIT(0)
> +
> +/**
> + * struct tcp_ddp_ulp_ops - Interface to register uppper layer Direct Data Placement (DDP) TCP offload
> + */
> +struct tcp_ddp_ulp_ops {
> + /* NIC requests ulp to indicate if @seq is the start of a message */
> + bool (*resync_request)(struct sock *sk, u32 seq, u32 flags);
> + /* NIC driver informs the ulp that ddp teardown is done - used for async completions*/
> + void (*ddp_teardown_done)(void *ddp_ctx);
> +};
> +
> +/**
> + * struct tcp_ddp_ctx - Generic tcp ddp context: device driver per queue contexts must
> + * use this as the first member.
> + */
> +struct tcp_ddp_ctx {
> + enum tcp_ddp_type type;
> + unsigned char buf[];
> +};
> +
> +static inline struct tcp_ddp_ctx *tcp_ddp_get_ctx(const struct sock *sk)
> +{
> + struct inet_connection_sock *icsk = inet_csk(sk);
> +
> + return (__force struct tcp_ddp_ctx *)icsk->icsk_ulp_ddp_data;
> +}
> +
> +static inline void tcp_ddp_set_ctx(struct sock *sk, void *ctx)
> +{
> + struct inet_connection_sock *icsk = inet_csk(sk);
> +
> + rcu_assign_pointer(icsk->icsk_ulp_ddp_data, ctx);
> +}
> +
> +#endif //_TCP_DDP_H
> diff --git a/net/Kconfig b/net/Kconfig
> index f4c32d982af6..3876861cdc90 100644
> --- a/net/Kconfig
> +++ b/net/Kconfig
> @@ -457,6 +457,15 @@ config ETHTOOL_NETLINK
> netlink. It provides better extensibility and some new features,
> e.g. notification messages.
>
> +config TCP_DDP
> + bool "TCP direct data placement offload"
> + default n
> + help
> + Direct Data Placement (DDP) offload for TCP enables ULP, such as
> + NVMe-TCP/iSCSI, to request the NIC to place TCP payload data
> + of a command response directly into kernel pages.
> +
> +
> endif # if NET
>
> # Used by archs to tell that they support BPF JIT compiler plus which flavour.
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index f62cae3f75d8..791c1b6bc067 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -69,6 +69,7 @@
> #include <net/xfrm.h>
> #include <net/mpls.h>
> #include <net/mptcp.h>
> +#include <net/tcp_ddp.h>
>
> #include <linux/uaccess.h>
> #include <trace/events/skb.h>
> @@ -6140,9 +6141,15 @@ EXPORT_SYMBOL(pskb_extract);
> */
> void skb_condense(struct sk_buff *skb)
> {
> + bool is_ddp = false;
> +
> +#ifdef CONFIG_TCP_DDP
This looks strange to me : TCP should call this helper while skb->sk is NULL
Are you sure this is not dead code ?
> + is_ddp = skb->sk && inet_csk(skb->sk) &&
> + inet_csk(skb->sk)->icsk_ulp_ddp_data;
> +#endif
> if (skb->data_len) {
> if (skb->data_len > skb->end - skb->tail ||
> - skb_cloned(skb))
> + skb_cloned(skb) || is_ddp)
> return;
>
> /* Nice, we can free page frag(s) right now */
> diff --git a/net/ethtool/common.c b/net/ethtool/common.c
> index 24036e3055a1..a2ff7a4a6bbf 100644
> --- a/net/ethtool/common.c
> +++ b/net/ethtool/common.c
> @@ -68,6 +68,7 @@ const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN] = {
> [NETIF_F_HW_TLS_RX_BIT] = "tls-hw-rx-offload",
> [NETIF_F_GRO_FRAGLIST_BIT] = "rx-gro-list",
> [NETIF_F_HW_MACSEC_BIT] = "macsec-hw-offload",
> + [NETIF_F_HW_TCP_DDP_BIT] = "tcp-ddp-offload",
> };
>
> const char
> --
> 2.24.1
>
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