1 // SPDX-License-Identifier: GPL-2.0 2 /* cpumap.c: used for optimizing CPU assignment 3 * 4 * Copyright (C) 2009 Hong H. Pham <hong.pham@windriver.com> 5 */ 6 7 #include <linux/export.h> 8 #include <linux/slab.h> 9 #include <linux/kernel.h> 10 #include <linux/cpumask.h> 11 #include <linux/spinlock.h> 12 #include <asm/cpudata.h> 13 #include "cpumap.h" 14 15 16 enum { 17 CPUINFO_LVL_ROOT = 0, 18 CPUINFO_LVL_NODE, 19 CPUINFO_LVL_CORE, 20 CPUINFO_LVL_PROC, 21 CPUINFO_LVL_MAX, 22 }; 23 24 enum { 25 ROVER_NO_OP = 0, 26 /* Increment rover every time level is visited */ 27 ROVER_INC_ON_VISIT = 1 << 0, 28 /* Increment parent's rover every time rover wraps around */ 29 ROVER_INC_PARENT_ON_LOOP = 1 << 1, 30 }; 31 32 struct cpuinfo_node { 33 int id; 34 int level; 35 int num_cpus; /* Number of CPUs in this hierarchy */ 36 int parent_index; 37 int child_start; /* Array index of the first child node */ 38 int child_end; /* Array index of the last child node */ 39 int rover; /* Child node iterator */ 40 }; 41 42 struct cpuinfo_level { 43 int start_index; /* Index of first node of a level in a cpuinfo tree */ 44 int end_index; /* Index of last node of a level in a cpuinfo tree */ 45 int num_nodes; /* Number of nodes in a level in a cpuinfo tree */ 46 }; 47 48 struct cpuinfo_tree { 49 int total_nodes; 50 51 /* Offsets into nodes[] for each level of the tree */ 52 struct cpuinfo_level level[CPUINFO_LVL_MAX]; 53 struct cpuinfo_node nodes[0]; 54 }; 55 56 57 static struct cpuinfo_tree *cpuinfo_tree; 58 59 static u16 cpu_distribution_map[NR_CPUS]; 60 static DEFINE_SPINLOCK(cpu_map_lock); 61 62 63 /* Niagara optimized cpuinfo tree traversal. */ 64 static const int niagara_iterate_method[] = { 65 [CPUINFO_LVL_ROOT] = ROVER_NO_OP, 66 67 /* Strands (or virtual CPUs) within a core may not run concurrently 68 * on the Niagara, as instruction pipeline(s) are shared. Distribute 69 * work to strands in different cores first for better concurrency. 70 * Go to next NUMA node when all cores are used. 71 */ 72 [CPUINFO_LVL_NODE] = ROVER_INC_ON_VISIT|ROVER_INC_PARENT_ON_LOOP, 73 74 /* Strands are grouped together by proc_id in cpuinfo_sparc, i.e. 75 * a proc_id represents an instruction pipeline. Distribute work to 76 * strands in different proc_id groups if the core has multiple 77 * instruction pipelines (e.g. the Niagara 2/2+ has two). 78 */ 79 [CPUINFO_LVL_CORE] = ROVER_INC_ON_VISIT, 80 81 /* Pick the next strand in the proc_id group. */ 82 [CPUINFO_LVL_PROC] = ROVER_INC_ON_VISIT, 83 }; 84 85 /* Generic cpuinfo tree traversal. Distribute work round robin across NUMA 86 * nodes. 87 */ 88 static const int generic_iterate_method[] = { 89 [CPUINFO_LVL_ROOT] = ROVER_INC_ON_VISIT, 90 [CPUINFO_LVL_NODE] = ROVER_NO_OP, 91 [CPUINFO_LVL_CORE] = ROVER_INC_PARENT_ON_LOOP, 92 [CPUINFO_LVL_PROC] = ROVER_INC_ON_VISIT|ROVER_INC_PARENT_ON_LOOP, 93 }; 94 95 96 static int cpuinfo_id(int cpu, int level) 97 { 98 int id; 99 100 switch (level) { 101 case CPUINFO_LVL_ROOT: 102 id = 0; 103 break; 104 case CPUINFO_LVL_NODE: 105 id = cpu_to_node(cpu); 106 break; 107 case CPUINFO_LVL_CORE: 108 id = cpu_data(cpu).core_id; 109 break; 110 case CPUINFO_LVL_PROC: 111 id = cpu_data(cpu).proc_id; 112 break; 113 default: 114 id = -EINVAL; 115 } 116 return id; 117 } 118 119 /* 120 * Enumerate the CPU information in __cpu_data to determine the start index, 121 * end index, and number of nodes for each level in the cpuinfo tree. The 122 * total number of cpuinfo nodes required to build the tree is returned. 123 */ 124 static int enumerate_cpuinfo_nodes(struct cpuinfo_level *tree_level) 125 { 126 int prev_id[CPUINFO_LVL_MAX]; 127 int i, n, num_nodes; 128 129 for (i = CPUINFO_LVL_ROOT; i < CPUINFO_LVL_MAX; i++) { 130 struct cpuinfo_level *lv = &tree_level[i]; 131 132 prev_id[i] = -1; 133 lv->start_index = lv->end_index = lv->num_nodes = 0; 134 } 135 136 num_nodes = 1; /* Include the root node */ 137 138 for (i = 0; i < num_possible_cpus(); i++) { 139 if (!cpu_online(i)) 140 continue; 141 142 n = cpuinfo_id(i, CPUINFO_LVL_NODE); 143 if (n > prev_id[CPUINFO_LVL_NODE]) { 144 tree_level[CPUINFO_LVL_NODE].num_nodes++; 145 prev_id[CPUINFO_LVL_NODE] = n; 146 num_nodes++; 147 } 148 n = cpuinfo_id(i, CPUINFO_LVL_CORE); 149 if (n > prev_id[CPUINFO_LVL_CORE]) { 150 tree_level[CPUINFO_LVL_CORE].num_nodes++; 151 prev_id[CPUINFO_LVL_CORE] = n; 152 num_nodes++; 153 } 154 n = cpuinfo_id(i, CPUINFO_LVL_PROC); 155 if (n > prev_id[CPUINFO_LVL_PROC]) { 156 tree_level[CPUINFO_LVL_PROC].num_nodes++; 157 prev_id[CPUINFO_LVL_PROC] = n; 158 num_nodes++; 159 } 160 } 161 162 tree_level[CPUINFO_LVL_ROOT].num_nodes = 1; 163 164 n = tree_level[CPUINFO_LVL_NODE].num_nodes; 165 tree_level[CPUINFO_LVL_NODE].start_index = 1; 166 tree_level[CPUINFO_LVL_NODE].end_index = n; 167 168 n++; 169 tree_level[CPUINFO_LVL_CORE].start_index = n; 170 n += tree_level[CPUINFO_LVL_CORE].num_nodes; 171 tree_level[CPUINFO_LVL_CORE].end_index = n - 1; 172 173 tree_level[CPUINFO_LVL_PROC].start_index = n; 174 n += tree_level[CPUINFO_LVL_PROC].num_nodes; 175 tree_level[CPUINFO_LVL_PROC].end_index = n - 1; 176 177 return num_nodes; 178 } 179 180 /* Build a tree representation of the CPU hierarchy using the per CPU 181 * information in __cpu_data. Entries in __cpu_data[0..NR_CPUS] are 182 * assumed to be sorted in ascending order based on node, core_id, and 183 * proc_id (in order of significance). 184 */ 185 static struct cpuinfo_tree *build_cpuinfo_tree(void) 186 { 187 struct cpuinfo_tree *new_tree; 188 struct cpuinfo_node *node; 189 struct cpuinfo_level tmp_level[CPUINFO_LVL_MAX]; 190 int num_cpus[CPUINFO_LVL_MAX]; 191 int level_rover[CPUINFO_LVL_MAX]; 192 int prev_id[CPUINFO_LVL_MAX]; 193 int n, id, cpu, prev_cpu, last_cpu, level; 194 195 n = enumerate_cpuinfo_nodes(tmp_level); 196 197 new_tree = kzalloc(struct_size(new_tree, nodes, n), GFP_ATOMIC); 198 if (!new_tree) 199 return NULL; 200 201 new_tree->total_nodes = n; 202 memcpy(&new_tree->level, tmp_level, sizeof(tmp_level)); 203 204 prev_cpu = cpu = cpumask_first(cpu_online_mask); 205 206 /* Initialize all levels in the tree with the first CPU */ 207 for (level = CPUINFO_LVL_PROC; level >= CPUINFO_LVL_ROOT; level--) { 208 n = new_tree->level[level].start_index; 209 210 level_rover[level] = n; 211 node = &new_tree->nodes[n]; 212 213 id = cpuinfo_id(cpu, level); 214 if (unlikely(id < 0)) { 215 kfree(new_tree); 216 return NULL; 217 } 218 node->id = id; 219 node->level = level; 220 node->num_cpus = 1; 221 222 node->parent_index = (level > CPUINFO_LVL_ROOT) 223 ? new_tree->level[level - 1].start_index : -1; 224 225 node->child_start = node->child_end = node->rover = 226 (level == CPUINFO_LVL_PROC) 227 ? cpu : new_tree->level[level + 1].start_index; 228 229 prev_id[level] = node->id; 230 num_cpus[level] = 1; 231 } 232 233 for (last_cpu = (num_possible_cpus() - 1); last_cpu >= 0; last_cpu--) { 234 if (cpu_online(last_cpu)) 235 break; 236 } 237 238 while (++cpu <= last_cpu) { 239 if (!cpu_online(cpu)) 240 continue; 241 242 for (level = CPUINFO_LVL_PROC; level >= CPUINFO_LVL_ROOT; 243 level--) { 244 id = cpuinfo_id(cpu, level); 245 if (unlikely(id < 0)) { 246 kfree(new_tree); 247 return NULL; 248 } 249 250 if ((id != prev_id[level]) || (cpu == last_cpu)) { 251 prev_id[level] = id; 252 node = &new_tree->nodes[level_rover[level]]; 253 node->num_cpus = num_cpus[level]; 254 num_cpus[level] = 1; 255 256 if (cpu == last_cpu) 257 node->num_cpus++; 258 259 /* Connect tree node to parent */ 260 if (level == CPUINFO_LVL_ROOT) 261 node->parent_index = -1; 262 else 263 node->parent_index = 264 level_rover[level - 1]; 265 266 if (level == CPUINFO_LVL_PROC) { 267 node->child_end = 268 (cpu == last_cpu) ? cpu : prev_cpu; 269 } else { 270 node->child_end = 271 level_rover[level + 1] - 1; 272 } 273 274 /* Initialize the next node in the same level */ 275 n = ++level_rover[level]; 276 if (n <= new_tree->level[level].end_index) { 277 node = &new_tree->nodes[n]; 278 node->id = id; 279 node->level = level; 280 281 /* Connect node to child */ 282 node->child_start = node->child_end = 283 node->rover = 284 (level == CPUINFO_LVL_PROC) 285 ? cpu : level_rover[level + 1]; 286 } 287 } else 288 num_cpus[level]++; 289 } 290 prev_cpu = cpu; 291 } 292 293 return new_tree; 294 } 295 296 static void increment_rover(struct cpuinfo_tree *t, int node_index, 297 int root_index, const int *rover_inc_table) 298 { 299 struct cpuinfo_node *node = &t->nodes[node_index]; 300 int top_level, level; 301 302 top_level = t->nodes[root_index].level; 303 for (level = node->level; level >= top_level; level--) { 304 node->rover++; 305 if (node->rover <= node->child_end) 306 return; 307 308 node->rover = node->child_start; 309 /* If parent's rover does not need to be adjusted, stop here. */ 310 if ((level == top_level) || 311 !(rover_inc_table[level] & ROVER_INC_PARENT_ON_LOOP)) 312 return; 313 314 node = &t->nodes[node->parent_index]; 315 } 316 } 317 318 static int iterate_cpu(struct cpuinfo_tree *t, unsigned int root_index) 319 { 320 const int *rover_inc_table; 321 int level, new_index, index = root_index; 322 323 switch (sun4v_chip_type) { 324 case SUN4V_CHIP_NIAGARA1: 325 case SUN4V_CHIP_NIAGARA2: 326 case SUN4V_CHIP_NIAGARA3: 327 case SUN4V_CHIP_NIAGARA4: 328 case SUN4V_CHIP_NIAGARA5: 329 case SUN4V_CHIP_SPARC_M6: 330 case SUN4V_CHIP_SPARC_M7: 331 case SUN4V_CHIP_SPARC_M8: 332 case SUN4V_CHIP_SPARC_SN: 333 case SUN4V_CHIP_SPARC64X: 334 rover_inc_table = niagara_iterate_method; 335 break; 336 default: 337 rover_inc_table = generic_iterate_method; 338 } 339 340 for (level = t->nodes[root_index].level; level < CPUINFO_LVL_MAX; 341 level++) { 342 new_index = t->nodes[index].rover; 343 if (rover_inc_table[level] & ROVER_INC_ON_VISIT) 344 increment_rover(t, index, root_index, rover_inc_table); 345 346 index = new_index; 347 } 348 return index; 349 } 350 351 static void _cpu_map_rebuild(void) 352 { 353 int i; 354 355 if (cpuinfo_tree) { 356 kfree(cpuinfo_tree); 357 cpuinfo_tree = NULL; 358 } 359 360 cpuinfo_tree = build_cpuinfo_tree(); 361 if (!cpuinfo_tree) 362 return; 363 364 /* Build CPU distribution map that spans all online CPUs. No need 365 * to check if the CPU is online, as that is done when the cpuinfo 366 * tree is being built. 367 */ 368 for (i = 0; i < cpuinfo_tree->nodes[0].num_cpus; i++) 369 cpu_distribution_map[i] = iterate_cpu(cpuinfo_tree, 0); 370 } 371 372 /* Fallback if the cpuinfo tree could not be built. CPU mapping is linear 373 * round robin. 374 */ 375 static int simple_map_to_cpu(unsigned int index) 376 { 377 int i, end, cpu_rover; 378 379 cpu_rover = 0; 380 end = index % num_online_cpus(); 381 for (i = 0; i < num_possible_cpus(); i++) { 382 if (cpu_online(cpu_rover)) { 383 if (cpu_rover >= end) 384 return cpu_rover; 385 386 cpu_rover++; 387 } 388 } 389 390 /* Impossible, since num_online_cpus() <= num_possible_cpus() */ 391 return cpumask_first(cpu_online_mask); 392 } 393 394 static int _map_to_cpu(unsigned int index) 395 { 396 struct cpuinfo_node *root_node; 397 398 if (unlikely(!cpuinfo_tree)) { 399 _cpu_map_rebuild(); 400 if (!cpuinfo_tree) 401 return simple_map_to_cpu(index); 402 } 403 404 root_node = &cpuinfo_tree->nodes[0]; 405 #ifdef CONFIG_HOTPLUG_CPU 406 if (unlikely(root_node->num_cpus != num_online_cpus())) { 407 _cpu_map_rebuild(); 408 if (!cpuinfo_tree) 409 return simple_map_to_cpu(index); 410 } 411 #endif 412 return cpu_distribution_map[index % root_node->num_cpus]; 413 } 414 415 int map_to_cpu(unsigned int index) 416 { 417 int mapped_cpu; 418 unsigned long flag; 419 420 spin_lock_irqsave(&cpu_map_lock, flag); 421 mapped_cpu = _map_to_cpu(index); 422 423 #ifdef CONFIG_HOTPLUG_CPU 424 while (unlikely(!cpu_online(mapped_cpu))) 425 mapped_cpu = _map_to_cpu(index); 426 #endif 427 spin_unlock_irqrestore(&cpu_map_lock, flag); 428 return mapped_cpu; 429 } 430 EXPORT_SYMBOL(map_to_cpu); 431 432 void cpu_map_rebuild(void) 433 { 434 unsigned long flag; 435 436 spin_lock_irqsave(&cpu_map_lock, flag); 437 _cpu_map_rebuild(); 438 spin_unlock_irqrestore(&cpu_map_lock, flag); 439 } 440