cache.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef __LINUX_CACHE_H
  3#define __LINUX_CACHE_H
  4
  5#include <uapi/linux/kernel.h>
  6#include <vdso/cache.h>
  7#include <asm/cache.h>
  8
  9#ifndef L1_CACHE_ALIGN
 10#define L1_CACHE_ALIGN(x) __ALIGN_KERNEL(x, L1_CACHE_BYTES)
 11#endif
 12
 13/**
 14 * SMP_CACHE_ALIGN - align a value to the L2 cacheline size
 15 * @x: value to align
 16 *
 17 * On some architectures, L2 ("SMP") CL size is bigger than L1, and sometimes,
 18 * this needs to be accounted.
 19 *
 20 * Return: aligned value.
 21 */
 22#ifndef SMP_CACHE_ALIGN
 23#define SMP_CACHE_ALIGN(x)	ALIGN(x, SMP_CACHE_BYTES)
 24#endif
 25
 26/*
 27 * ``__aligned_largest`` aligns a field to the value most optimal for the
 28 * target architecture to perform memory operations. Get the actual value
 29 * to be able to use it anywhere else.
 30 */
 31#ifndef __LARGEST_ALIGN
 32#define __LARGEST_ALIGN		sizeof(struct { long x; } __aligned_largest)
 33#endif
 34
 35#ifndef LARGEST_ALIGN
 36#define LARGEST_ALIGN(x)	ALIGN(x, __LARGEST_ALIGN)
 37#endif
 38
 39/*
 40 * __read_mostly is used to keep rarely changing variables out of frequently
 41 * updated cachelines. Its use should be reserved for data that is used
 42 * frequently in hot paths. Performance traces can help decide when to use
 43 * this. You want __read_mostly data to be tightly packed, so that in the
 44 * best case multiple frequently read variables for a hot path will be next
 45 * to each other in order to reduce the number of cachelines needed to
 46 * execute a critical path. We should be mindful and selective of its use.
 47 * ie: if you're going to use it please supply a *good* justification in your
 48 * commit log
 49 */
 50#ifndef __read_mostly
 51#define __read_mostly
 52#endif
 53
 54/*
 55 * __ro_after_init is used to mark things that are read-only after init (i.e.
 56 * after mark_rodata_ro() has been called). These are effectively read-only,
 57 * but may get written to during init, so can't live in .rodata (via "const").
 58 */
 59#ifndef __ro_after_init
 60#define __ro_after_init __section(".data..ro_after_init")
 61#endif
 62
 63#ifndef ____cacheline_aligned_in_smp
 64#ifdef CONFIG_SMP
 65#define ____cacheline_aligned_in_smp ____cacheline_aligned
 66#else
 67#define ____cacheline_aligned_in_smp
 68#endif /* CONFIG_SMP */
 69#endif
 70
 71#ifndef __cacheline_aligned
 72#define __cacheline_aligned					\
 73  __attribute__((__aligned__(SMP_CACHE_BYTES),			\
 74		 __section__(".data..cacheline_aligned")))
 75#endif /* __cacheline_aligned */
 76
 77#ifndef __cacheline_aligned_in_smp
 78#ifdef CONFIG_SMP
 79#define __cacheline_aligned_in_smp __cacheline_aligned
 80#else
 81#define __cacheline_aligned_in_smp
 82#endif /* CONFIG_SMP */
 83#endif
 84
 85/*
 86 * The maximum alignment needed for some critical structures
 87 * These could be inter-node cacheline sizes/L3 cacheline
 88 * size etc.  Define this in asm/cache.h for your arch
 89 */
 90#ifndef INTERNODE_CACHE_SHIFT
 91#define INTERNODE_CACHE_SHIFT L1_CACHE_SHIFT
 92#endif
 93
 94#if !defined(____cacheline_internodealigned_in_smp)
 95#if defined(CONFIG_SMP)
 96#define ____cacheline_internodealigned_in_smp \
 97	__attribute__((__aligned__(1 << (INTERNODE_CACHE_SHIFT))))
 98#else
 99#define ____cacheline_internodealigned_in_smp
100#endif
101#endif
102
103#ifndef CONFIG_ARCH_HAS_CACHE_LINE_SIZE
104#define cache_line_size()	L1_CACHE_BYTES
105#endif
106
107#ifndef __cacheline_group_begin
108#define __cacheline_group_begin(GROUP) \
109	__u8 __cacheline_group_begin__##GROUP[0]
110#endif
111
112#ifndef __cacheline_group_end
113#define __cacheline_group_end(GROUP) \
114	__u8 __cacheline_group_end__##GROUP[0]
115#endif
116
117/**
118 * __cacheline_group_begin_aligned - declare an aligned group start
119 * @GROUP: name of the group
120 * @...: optional group alignment
121 *
122 * The following block inside a struct:
123 *
124 *	__cacheline_group_begin_aligned(grp);
125 *	field a;
126 *	field b;
127 *	__cacheline_group_end_aligned(grp);
128 *
129 * will always be aligned to either the specified alignment or
130 * ``SMP_CACHE_BYTES``.
131 */
132#define __cacheline_group_begin_aligned(GROUP, ...)		\
133	__cacheline_group_begin(GROUP)				\
134	__aligned((__VA_ARGS__ + 0) ? : SMP_CACHE_BYTES)
135
136/**
137 * __cacheline_group_end_aligned - declare an aligned group end
138 * @GROUP: name of the group
139 * @...: optional alignment (same as was in __cacheline_group_begin_aligned())
140 *
141 * Note that the end marker is aligned to sizeof(long) to allow more precise
142 * size assertion. It also declares a padding at the end to avoid next field
143 * falling into this cacheline.
144 */
145#define __cacheline_group_end_aligned(GROUP, ...)		\
146	__cacheline_group_end(GROUP) __aligned(sizeof(long));	\
147	struct { } __cacheline_group_pad__##GROUP		\
148	__aligned((__VA_ARGS__ + 0) ? : SMP_CACHE_BYTES)
149
150#ifndef CACHELINE_ASSERT_GROUP_MEMBER
151#define CACHELINE_ASSERT_GROUP_MEMBER(TYPE, GROUP, MEMBER) \
152	BUILD_BUG_ON(!(offsetof(TYPE, MEMBER) >= \
153		       offsetofend(TYPE, __cacheline_group_begin__##GROUP) && \
154		       offsetofend(TYPE, MEMBER) <= \
155		       offsetof(TYPE, __cacheline_group_end__##GROUP)))
156#endif
157
158#ifndef CACHELINE_ASSERT_GROUP_SIZE
159#define CACHELINE_ASSERT_GROUP_SIZE(TYPE, GROUP, SIZE) \
160	BUILD_BUG_ON(offsetof(TYPE, __cacheline_group_end__##GROUP) - \
161		     offsetofend(TYPE, __cacheline_group_begin__##GROUP) > \
162		     SIZE)
163#endif
164
165/*
166 * Helper to add padding within a struct to ensure data fall into separate
167 * cachelines.
168 */
169#if defined(CONFIG_SMP)
170struct cacheline_padding {
171	char x[0];
172} ____cacheline_internodealigned_in_smp;
173#define CACHELINE_PADDING(name)		struct cacheline_padding name
174#else
175#define CACHELINE_PADDING(name)
176#endif
177
178#ifdef ARCH_DMA_MINALIGN
179#define ARCH_HAS_DMA_MINALIGN
180#else
181#define ARCH_DMA_MINALIGN __alignof__(unsigned long long)
182#endif
183
184#endif /* __LINUX_CACHE_H */