1/* SPDX-License-Identifier: GPL-2.0-or-later */
  2#ifndef _NET_RPS_H
  3#define _NET_RPS_H
  4
  5#include <linux/types.h>
  6#include <linux/static_key.h>
  7#include <net/sock.h>
  8#include <net/hotdata.h>
  9
 10#ifdef CONFIG_RPS
 11
 12extern struct static_key_false rps_needed;
 13extern struct static_key_false rfs_needed;
 14
 15/*
 16 * This structure holds an RPS map which can be of variable length.  The
 17 * map is an array of CPUs.
 18 */
 19struct rps_map {
 20	unsigned int	len;
 21	struct rcu_head	rcu;
 22	u16		cpus[];
 23};
 24#define RPS_MAP_SIZE(_num) (sizeof(struct rps_map) + ((_num) * sizeof(u16)))
 25
 26/*
 27 * The rps_dev_flow structure contains the mapping of a flow to a CPU, the
 28 * tail pointer for that CPU's input queue at the time of last enqueue, and
 29 * a hardware filter index.
 30 */
 31struct rps_dev_flow {
 32	u16		cpu;
 33	u16		filter;
 34	unsigned int	last_qtail;
 35};
 36#define RPS_NO_FILTER 0xffff
 37
 38/*
 39 * The rps_dev_flow_table structure contains a table of flow mappings.
 40 */
 41struct rps_dev_flow_table {
 42	unsigned int		mask;
 43	struct rcu_head		rcu;
 44	struct rps_dev_flow	flows[];
 45};
 46#define RPS_DEV_FLOW_TABLE_SIZE(_num) (sizeof(struct rps_dev_flow_table) + \
 47    ((_num) * sizeof(struct rps_dev_flow)))
 48
 49/*
 50 * The rps_sock_flow_table contains mappings of flows to the last CPU
 51 * on which they were processed by the application (set in recvmsg).
 52 * Each entry is a 32bit value. Upper part is the high-order bits
 53 * of flow hash, lower part is CPU number.
 54 * rps_cpu_mask is used to partition the space, depending on number of
 55 * possible CPUs : rps_cpu_mask = roundup_pow_of_two(nr_cpu_ids) - 1
 56 * For example, if 64 CPUs are possible, rps_cpu_mask = 0x3f,
 57 * meaning we use 32-6=26 bits for the hash.
 58 */
 59struct rps_sock_flow_table {
 60	u32	mask;
 61
 62	u32	ents[] ____cacheline_aligned_in_smp;
 63};
 64#define	RPS_SOCK_FLOW_TABLE_SIZE(_num) (offsetof(struct rps_sock_flow_table, ents[_num]))
 65
 66#define RPS_NO_CPU 0xffff
 67
 68static inline void rps_record_sock_flow(struct rps_sock_flow_table *table,
 69					u32 hash)
 70{
 71	unsigned int index = hash & table->mask;
 72	u32 val = hash & ~net_hotdata.rps_cpu_mask;
 73
 74	/* We only give a hint, preemption can change CPU under us */
 75	val |= raw_smp_processor_id();
 76
 77	/* The following WRITE_ONCE() is paired with the READ_ONCE()
 78	 * here, and another one in get_rps_cpu().
 79	 */
 80	if (READ_ONCE(table->ents[index]) != val)
 81		WRITE_ONCE(table->ents[index], val);
 82}
 83
 84#endif /* CONFIG_RPS */
 85
 86static inline void sock_rps_record_flow_hash(__u32 hash)
 87{
 88#ifdef CONFIG_RPS
 89	struct rps_sock_flow_table *sock_flow_table;
 90
 91	if (!hash)
 92		return;
 93	rcu_read_lock();
 94	sock_flow_table = rcu_dereference(net_hotdata.rps_sock_flow_table);
 95	if (sock_flow_table)
 96		rps_record_sock_flow(sock_flow_table, hash);
 97	rcu_read_unlock();
 98#endif
 99}
100
101static inline void sock_rps_record_flow(const struct sock *sk)
102{
103#ifdef CONFIG_RPS
104	if (static_branch_unlikely(&rfs_needed)) {
105		/* Reading sk->sk_rxhash might incur an expensive cache line
106		 * miss.
107		 *
108		 * TCP_ESTABLISHED does cover almost all states where RFS
109		 * might be useful, and is cheaper [1] than testing :
110		 *	IPv4: inet_sk(sk)->inet_daddr
111		 * 	IPv6: ipv6_addr_any(&sk->sk_v6_daddr)
112		 * OR	an additional socket flag
113		 * [1] : sk_state and sk_prot are in the same cache line.
114		 */
115		if (sk->sk_state == TCP_ESTABLISHED) {
116			/* This READ_ONCE() is paired with the WRITE_ONCE()
117			 * from sock_rps_save_rxhash() and sock_rps_reset_rxhash().
118			 */
119			sock_rps_record_flow_hash(READ_ONCE(sk->sk_rxhash));
120		}
121	}
122#endif
123}
124
125static inline u32 rps_input_queue_tail_incr(struct softnet_data *sd)
126{
127#ifdef CONFIG_RPS
128	return ++sd->input_queue_tail;
129#else
130	return 0;
131#endif
132}
133
134static inline void rps_input_queue_tail_save(u32 *dest, u32 tail)
135{
136#ifdef CONFIG_RPS
137	WRITE_ONCE(*dest, tail);
138#endif
139}
140
141static inline void rps_input_queue_head_add(struct softnet_data *sd, int val)
142{
143#ifdef CONFIG_RPS
144	WRITE_ONCE(sd->input_queue_head, sd->input_queue_head + val);
145#endif
146}
147
148static inline void rps_input_queue_head_incr(struct softnet_data *sd)
149{
150	rps_input_queue_head_add(sd, 1);
151}
152
153#endif /* _NET_RPS_H */