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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * cpu_rmap.c: CPU affinity reverse-map support
4 * Copyright 2011 Solarflare Communications Inc.
5 */
6
7#include <linux/cpu_rmap.h>
8#include <linux/interrupt.h>
9#include <linux/export.h>
10
11/*
12 * These functions maintain a mapping from CPUs to some ordered set of
13 * objects with CPU affinities. This can be seen as a reverse-map of
14 * CPU affinity. However, we do not assume that the object affinities
15 * cover all CPUs in the system. For those CPUs not directly covered
16 * by object affinities, we attempt to find a nearest object based on
17 * CPU topology.
18 */
19
20/**
21 * alloc_cpu_rmap - allocate CPU affinity reverse-map
22 * @size: Number of objects to be mapped
23 * @flags: Allocation flags e.g. %GFP_KERNEL
24 */
25struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags)
26{
27 struct cpu_rmap *rmap;
28 unsigned int cpu;
29 size_t obj_offset;
30
31 /* This is a silly number of objects, and we use u16 indices. */
32 if (size > 0xffff)
33 return NULL;
34
35 /* Offset of object pointer array from base structure */
36 obj_offset = ALIGN(offsetof(struct cpu_rmap, near[nr_cpu_ids]),
37 sizeof(void *));
38
39 rmap = kzalloc(obj_offset + size * sizeof(rmap->obj[0]), flags);
40 if (!rmap)
41 return NULL;
42
43 kref_init(&rmap->refcount);
44 rmap->obj = (void **)((char *)rmap + obj_offset);
45
46 /* Initially assign CPUs to objects on a rota, since we have
47 * no idea where the objects are. Use infinite distance, so
48 * any object with known distance is preferable. Include the
49 * CPUs that are not present/online, since we definitely want
50 * any newly-hotplugged CPUs to have some object assigned.
51 */
52 for_each_possible_cpu(cpu) {
53 rmap->near[cpu].index = cpu % size;
54 rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
55 }
56
57 rmap->size = size;
58 return rmap;
59}
60EXPORT_SYMBOL(alloc_cpu_rmap);
61
62/**
63 * cpu_rmap_release - internal reclaiming helper called from kref_put
64 * @ref: kref to struct cpu_rmap
65 */
66static void cpu_rmap_release(struct kref *ref)
67{
68 struct cpu_rmap *rmap = container_of(ref, struct cpu_rmap, refcount);
69 kfree(rmap);
70}
71
72/**
73 * cpu_rmap_get - internal helper to get new ref on a cpu_rmap
74 * @rmap: reverse-map allocated with alloc_cpu_rmap()
75 */
76void cpu_rmap_get(struct cpu_rmap *rmap)
77{
78 kref_get(&rmap->refcount);
79}
80
81/**
82 * cpu_rmap_put - release ref on a cpu_rmap
83 * @rmap: reverse-map allocated with alloc_cpu_rmap()
84 */
85int cpu_rmap_put(struct cpu_rmap *rmap)
86{
87 return kref_put(&rmap->refcount, cpu_rmap_release);
88}
89EXPORT_SYMBOL(cpu_rmap_put);
90
91/* Reevaluate nearest object for given CPU, comparing with the given
92 * neighbours at the given distance.
93 */
94static bool cpu_rmap_copy_neigh(struct cpu_rmap *rmap, unsigned int cpu,
95 const struct cpumask *mask, u16 dist)
96{
97 int neigh;
98
99 for_each_cpu(neigh, mask) {
100 if (rmap->near[cpu].dist > dist &&
101 rmap->near[neigh].dist <= dist) {
102 rmap->near[cpu].index = rmap->near[neigh].index;
103 rmap->near[cpu].dist = dist;
104 return true;
105 }
106 }
107 return false;
108}
109
110#ifdef DEBUG
111static void debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
112{
113 unsigned index;
114 unsigned int cpu;
115
116 pr_info("cpu_rmap %p, %s:\n", rmap, prefix);
117
118 for_each_possible_cpu(cpu) {
119 index = rmap->near[cpu].index;
120 pr_info("cpu %d -> obj %u (distance %u)\n",
121 cpu, index, rmap->near[cpu].dist);
122 }
123}
124#else
125static inline void
126debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
127{
128}
129#endif
130
131static int get_free_index(struct cpu_rmap *rmap)
132{
133 int i;
134
135 for (i = 0; i < rmap->size; i++)
136 if (!rmap->obj[i])
137 return i;
138
139 return -ENOSPC;
140}
141
142/**
143 * cpu_rmap_add - add object to a rmap
144 * @rmap: CPU rmap allocated with alloc_cpu_rmap()
145 * @obj: Object to add to rmap
146 *
147 * Return index of object or -ENOSPC if no free entry was found
148 */
149int cpu_rmap_add(struct cpu_rmap *rmap, void *obj)
150{
151 int index = get_free_index(rmap);
152
153 if (index < 0)
154 return index;
155
156 rmap->obj[index] = obj;
157 return index;
158}
159EXPORT_SYMBOL(cpu_rmap_add);
160
161/**
162 * cpu_rmap_update - update CPU rmap following a change of object affinity
163 * @rmap: CPU rmap to update
164 * @index: Index of object whose affinity changed
165 * @affinity: New CPU affinity of object
166 */
167int cpu_rmap_update(struct cpu_rmap *rmap, u16 index,
168 const struct cpumask *affinity)
169{
170 cpumask_var_t update_mask;
171 unsigned int cpu;
172
173 if (unlikely(!zalloc_cpumask_var(&update_mask, GFP_KERNEL)))
174 return -ENOMEM;
175
176 /* Invalidate distance for all CPUs for which this used to be
177 * the nearest object. Mark those CPUs for update.
178 */
179 for_each_online_cpu(cpu) {
180 if (rmap->near[cpu].index == index) {
181 rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
182 cpumask_set_cpu(cpu, update_mask);
183 }
184 }
185
186 debug_print_rmap(rmap, "after invalidating old distances");
187
188 /* Set distance to 0 for all CPUs in the new affinity mask.
189 * Mark all CPUs within their NUMA nodes for update.
190 */
191 for_each_cpu(cpu, affinity) {
192 rmap->near[cpu].index = index;
193 rmap->near[cpu].dist = 0;
194 cpumask_or(update_mask, update_mask,
195 cpumask_of_node(cpu_to_node(cpu)));
196 }
197
198 debug_print_rmap(rmap, "after updating neighbours");
199
200 /* Update distances based on topology */
201 for_each_cpu(cpu, update_mask) {
202 if (cpu_rmap_copy_neigh(rmap, cpu,
203 topology_sibling_cpumask(cpu), 1))
204 continue;
205 if (cpu_rmap_copy_neigh(rmap, cpu,
206 topology_core_cpumask(cpu), 2))
207 continue;
208 if (cpu_rmap_copy_neigh(rmap, cpu,
209 cpumask_of_node(cpu_to_node(cpu)), 3))
210 continue;
211 /* We could continue into NUMA node distances, but for now
212 * we give up.
213 */
214 }
215
216 debug_print_rmap(rmap, "after copying neighbours");
217
218 free_cpumask_var(update_mask);
219 return 0;
220}
221EXPORT_SYMBOL(cpu_rmap_update);
222
223/* Glue between IRQ affinity notifiers and CPU rmaps */
224
225struct irq_glue {
226 struct irq_affinity_notify notify;
227 struct cpu_rmap *rmap;
228 u16 index;
229};
230
231/**
232 * free_irq_cpu_rmap - free a CPU affinity reverse-map used for IRQs
233 * @rmap: Reverse-map allocated with alloc_irq_cpu_map(), or %NULL
234 *
235 * Must be called in process context, before freeing the IRQs.
236 */
237void free_irq_cpu_rmap(struct cpu_rmap *rmap)
238{
239 struct irq_glue *glue;
240 u16 index;
241
242 if (!rmap)
243 return;
244
245 for (index = 0; index < rmap->size; index++) {
246 glue = rmap->obj[index];
247 if (glue)
248 irq_set_affinity_notifier(glue->notify.irq, NULL);
249 }
250
251 cpu_rmap_put(rmap);
252}
253EXPORT_SYMBOL(free_irq_cpu_rmap);
254
255/**
256 * irq_cpu_rmap_notify - callback for IRQ subsystem when IRQ affinity updated
257 * @notify: struct irq_affinity_notify passed by irq/manage.c
258 * @mask: cpu mask for new SMP affinity
259 *
260 * This is executed in workqueue context.
261 */
262static void
263irq_cpu_rmap_notify(struct irq_affinity_notify *notify, const cpumask_t *mask)
264{
265 struct irq_glue *glue =
266 container_of(notify, struct irq_glue, notify);
267 int rc;
268
269 rc = cpu_rmap_update(glue->rmap, glue->index, mask);
270 if (rc)
271 pr_warn("irq_cpu_rmap_notify: update failed: %d\n", rc);
272}
273
274/**
275 * irq_cpu_rmap_release - reclaiming callback for IRQ subsystem
276 * @ref: kref to struct irq_affinity_notify passed by irq/manage.c
277 */
278static void irq_cpu_rmap_release(struct kref *ref)
279{
280 struct irq_glue *glue =
281 container_of(ref, struct irq_glue, notify.kref);
282
283 glue->rmap->obj[glue->index] = NULL;
284 cpu_rmap_put(glue->rmap);
285 kfree(glue);
286}
287
288/**
289 * irq_cpu_rmap_remove - remove an IRQ from a CPU affinity reverse-map
290 * @rmap: The reverse-map
291 * @irq: The IRQ number
292 */
293int irq_cpu_rmap_remove(struct cpu_rmap *rmap, int irq)
294{
295 return irq_set_affinity_notifier(irq, NULL);
296}
297EXPORT_SYMBOL(irq_cpu_rmap_remove);
298
299/**
300 * irq_cpu_rmap_add - add an IRQ to a CPU affinity reverse-map
301 * @rmap: The reverse-map
302 * @irq: The IRQ number
303 *
304 * This adds an IRQ affinity notifier that will update the reverse-map
305 * automatically.
306 *
307 * Must be called in process context, after the IRQ is allocated but
308 * before it is bound with request_irq().
309 */
310int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq)
311{
312 struct irq_glue *glue = kzalloc_obj(*glue);
313 int rc;
314
315 if (!glue)
316 return -ENOMEM;
317 glue->notify.notify = irq_cpu_rmap_notify;
318 glue->notify.release = irq_cpu_rmap_release;
319 glue->rmap = rmap;
320 cpu_rmap_get(rmap);
321 rc = cpu_rmap_add(rmap, glue);
322 if (rc < 0)
323 goto err_add;
324
325 glue->index = rc;
326 rc = irq_set_affinity_notifier(irq, &glue->notify);
327 if (rc)
328 goto err_set;
329
330 return rc;
331
332err_set:
333 rmap->obj[glue->index] = NULL;
334err_add:
335 cpu_rmap_put(glue->rmap);
336 kfree(glue);
337 return rc;
338}
339EXPORT_SYMBOL(irq_cpu_rmap_add);