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
16enum {
17	CPUINFO_LVL_ROOT = 0,
18	CPUINFO_LVL_NODE,
19	CPUINFO_LVL_CORE,
20	CPUINFO_LVL_PROC,
21	CPUINFO_LVL_MAX,
22};
23
24enum {
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
32struct 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
42struct 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
48struct 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[] __counted_by(total_nodes);
54};
55
56
57static struct cpuinfo_tree *cpuinfo_tree;
58
59static u16 cpu_distribution_map[NR_CPUS];
60static DEFINE_SPINLOCK(cpu_map_lock);
61
62
63/* Niagara optimized cpuinfo tree traversal. */
64static 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 */
88static 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
96static 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 */
124static 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 */
185static 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
296static 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
318static 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
351static 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 */
375static 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
394static 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
415int 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}
430EXPORT_SYMBOL(map_to_cpu);
431
432void 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