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 <asm/cache.h> 7 8 #ifndef L1_CACHE_ALIGN 9 #define L1_CACHE_ALIGN(x) __ALIGN_KERNEL(x, L1_CACHE_BYTES) 10 #endif 11 12 #ifndef SMP_CACHE_BYTES 13 #define SMP_CACHE_BYTES L1_CACHE_BYTES 14 #endif 15 16 /** 17 * SMP_CACHE_ALIGN - align a value to the L2 cacheline size 18 * @x: value to align 19 * 20 * On some architectures, L2 ("SMP") CL size is bigger than L1, and sometimes, 21 * this needs to be accounted. 22 * 23 * Return: aligned value. 24 */ 25 #ifndef SMP_CACHE_ALIGN 26 #define SMP_CACHE_ALIGN(x) ALIGN(x, SMP_CACHE_BYTES) 27 #endif 28 29 /* 30 * ``__aligned_largest`` aligns a field to the value most optimal for the 31 * target architecture to perform memory operations. Get the actual value 32 * to be able to use it anywhere else. 33 */ 34 #ifndef __LARGEST_ALIGN 35 #define __LARGEST_ALIGN sizeof(struct { long x; } __aligned_largest) 36 #endif 37 38 #ifndef LARGEST_ALIGN 39 #define LARGEST_ALIGN(x) ALIGN(x, __LARGEST_ALIGN) 40 #endif 41 42 /* 43 * __read_mostly is used to keep rarely changing variables out of frequently 44 * updated cachelines. Its use should be reserved for data that is used 45 * frequently in hot paths. Performance traces can help decide when to use 46 * this. You want __read_mostly data to be tightly packed, so that in the 47 * best case multiple frequently read variables for a hot path will be next 48 * to each other in order to reduce the number of cachelines needed to 49 * execute a critical path. We should be mindful and selective of its use. 50 * ie: if you're going to use it please supply a *good* justification in your 51 * commit log 52 */ 53 #ifndef __read_mostly 54 #define __read_mostly 55 #endif 56 57 /* 58 * __ro_after_init is used to mark things that are read-only after init (i.e. 59 * after mark_rodata_ro() has been called). These are effectively read-only, 60 * but may get written to during init, so can't live in .rodata (via "const"). 61 */ 62 #ifndef __ro_after_init 63 #define __ro_after_init __section(".data..ro_after_init") 64 #endif 65 66 #ifndef ____cacheline_aligned 67 #define ____cacheline_aligned __attribute__((__aligned__(SMP_CACHE_BYTES))) 68 #endif 69 70 #ifndef ____cacheline_aligned_in_smp 71 #ifdef CONFIG_SMP 72 #define ____cacheline_aligned_in_smp ____cacheline_aligned 73 #else 74 #define ____cacheline_aligned_in_smp 75 #endif /* CONFIG_SMP */ 76 #endif 77 78 #ifndef __cacheline_aligned 79 #define __cacheline_aligned \ 80 __attribute__((__aligned__(SMP_CACHE_BYTES), \ 81 __section__(".data..cacheline_aligned"))) 82 #endif /* __cacheline_aligned */ 83 84 #ifndef __cacheline_aligned_in_smp 85 #ifdef CONFIG_SMP 86 #define __cacheline_aligned_in_smp __cacheline_aligned 87 #else 88 #define __cacheline_aligned_in_smp 89 #endif /* CONFIG_SMP */ 90 #endif 91 92 /* 93 * The maximum alignment needed for some critical structures 94 * These could be inter-node cacheline sizes/L3 cacheline 95 * size etc. Define this in asm/cache.h for your arch 96 */ 97 #ifndef INTERNODE_CACHE_SHIFT 98 #define INTERNODE_CACHE_SHIFT L1_CACHE_SHIFT 99 #endif 100 101 #if !defined(____cacheline_internodealigned_in_smp) 102 #if defined(CONFIG_SMP) 103 #define ____cacheline_internodealigned_in_smp \ 104 __attribute__((__aligned__(1 << (INTERNODE_CACHE_SHIFT)))) 105 #else 106 #define ____cacheline_internodealigned_in_smp 107 #endif 108 #endif 109 110 #ifndef CONFIG_ARCH_HAS_CACHE_LINE_SIZE 111 #define cache_line_size() L1_CACHE_BYTES 112 #endif 113 114 #ifndef __cacheline_group_begin 115 #define __cacheline_group_begin(GROUP) \ 116 __u8 __cacheline_group_begin__##GROUP[0] 117 #endif 118 119 #ifndef __cacheline_group_end 120 #define __cacheline_group_end(GROUP) \ 121 __u8 __cacheline_group_end__##GROUP[0] 122 #endif 123 124 /** 125 * __cacheline_group_begin_aligned - declare an aligned group start 126 * @GROUP: name of the group 127 * @...: optional group alignment 128 * 129 * The following block inside a struct: 130 * 131 * __cacheline_group_begin_aligned(grp); 132 * field a; 133 * field b; 134 * __cacheline_group_end_aligned(grp); 135 * 136 * will always be aligned to either the specified alignment or 137 * ``SMP_CACHE_BYTES``. 138 */ 139 #define __cacheline_group_begin_aligned(GROUP, ...) \ 140 __cacheline_group_begin(GROUP) \ 141 __aligned((__VA_ARGS__ + 0) ? : SMP_CACHE_BYTES) 142 143 /** 144 * __cacheline_group_end_aligned - declare an aligned group end 145 * @GROUP: name of the group 146 * @...: optional alignment (same as was in __cacheline_group_begin_aligned()) 147 * 148 * Note that the end marker is aligned to sizeof(long) to allow more precise 149 * size assertion. It also declares a padding at the end to avoid next field 150 * falling into this cacheline. 151 */ 152 #define __cacheline_group_end_aligned(GROUP, ...) \ 153 __cacheline_group_end(GROUP) __aligned(sizeof(long)); \ 154 struct { } __cacheline_group_pad__##GROUP \ 155 __aligned((__VA_ARGS__ + 0) ? : SMP_CACHE_BYTES) 156 157 #ifndef CACHELINE_ASSERT_GROUP_MEMBER 158 #define CACHELINE_ASSERT_GROUP_MEMBER(TYPE, GROUP, MEMBER) \ 159 BUILD_BUG_ON(!(offsetof(TYPE, MEMBER) >= \ 160 offsetofend(TYPE, __cacheline_group_begin__##GROUP) && \ 161 offsetofend(TYPE, MEMBER) <= \ 162 offsetof(TYPE, __cacheline_group_end__##GROUP))) 163 #endif 164 165 #ifndef CACHELINE_ASSERT_GROUP_SIZE 166 #define CACHELINE_ASSERT_GROUP_SIZE(TYPE, GROUP, SIZE) \ 167 BUILD_BUG_ON(offsetof(TYPE, __cacheline_group_end__##GROUP) - \ 168 offsetofend(TYPE, __cacheline_group_begin__##GROUP) > \ 169 SIZE) 170 #endif 171 172 /* 173 * Helper to add padding within a struct to ensure data fall into separate 174 * cachelines. 175 */ 176 #if defined(CONFIG_SMP) 177 struct cacheline_padding { 178 char x[0]; 179 } ____cacheline_internodealigned_in_smp; 180 #define CACHELINE_PADDING(name) struct cacheline_padding name 181 #else 182 #define CACHELINE_PADDING(name) 183 #endif 184 185 #ifdef ARCH_DMA_MINALIGN 186 #define ARCH_HAS_DMA_MINALIGN 187 #else 188 #define ARCH_DMA_MINALIGN __alignof__(unsigned long long) 189 #endif 190 191 #endif /* __LINUX_CACHE_H */ 192