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 */
alloc_cpu_rmap(unsigned int size,gfp_t flags)25 struct 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 }
60 EXPORT_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 */
cpu_rmap_release(struct kref * ref)66 static 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 */
cpu_rmap_get(struct cpu_rmap * rmap)76 static inline void 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 */
cpu_rmap_put(struct cpu_rmap * rmap)85 int cpu_rmap_put(struct cpu_rmap *rmap)
86 {
87 return kref_put(&rmap->refcount, cpu_rmap_release);
88 }
89 EXPORT_SYMBOL(cpu_rmap_put);
90
91 /* Reevaluate nearest object for given CPU, comparing with the given
92 * neighbours at the given distance.
93 */
cpu_rmap_copy_neigh(struct cpu_rmap * rmap,unsigned int cpu,const struct cpumask * mask,u16 dist)94 static 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
debug_print_rmap(const struct cpu_rmap * rmap,const char * prefix)111 static 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
125 static inline void
debug_print_rmap(const struct cpu_rmap * rmap,const char * prefix)126 debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
127 {
128 }
129 #endif
130
131 /**
132 * cpu_rmap_add - add object to a rmap
133 * @rmap: CPU rmap allocated with alloc_cpu_rmap()
134 * @obj: Object to add to rmap
135 *
136 * Return index of object.
137 */
cpu_rmap_add(struct cpu_rmap * rmap,void * obj)138 int cpu_rmap_add(struct cpu_rmap *rmap, void *obj)
139 {
140 u16 index;
141
142 BUG_ON(rmap->used >= rmap->size);
143 index = rmap->used++;
144 rmap->obj[index] = obj;
145 return index;
146 }
147 EXPORT_SYMBOL(cpu_rmap_add);
148
149 /**
150 * cpu_rmap_update - update CPU rmap following a change of object affinity
151 * @rmap: CPU rmap to update
152 * @index: Index of object whose affinity changed
153 * @affinity: New CPU affinity of object
154 */
cpu_rmap_update(struct cpu_rmap * rmap,u16 index,const struct cpumask * affinity)155 int cpu_rmap_update(struct cpu_rmap *rmap, u16 index,
156 const struct cpumask *affinity)
157 {
158 cpumask_var_t update_mask;
159 unsigned int cpu;
160
161 if (unlikely(!zalloc_cpumask_var(&update_mask, GFP_KERNEL)))
162 return -ENOMEM;
163
164 /* Invalidate distance for all CPUs for which this used to be
165 * the nearest object. Mark those CPUs for update.
166 */
167 for_each_online_cpu(cpu) {
168 if (rmap->near[cpu].index == index) {
169 rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
170 cpumask_set_cpu(cpu, update_mask);
171 }
172 }
173
174 debug_print_rmap(rmap, "after invalidating old distances");
175
176 /* Set distance to 0 for all CPUs in the new affinity mask.
177 * Mark all CPUs within their NUMA nodes for update.
178 */
179 for_each_cpu(cpu, affinity) {
180 rmap->near[cpu].index = index;
181 rmap->near[cpu].dist = 0;
182 cpumask_or(update_mask, update_mask,
183 cpumask_of_node(cpu_to_node(cpu)));
184 }
185
186 debug_print_rmap(rmap, "after updating neighbours");
187
188 /* Update distances based on topology */
189 for_each_cpu(cpu, update_mask) {
190 if (cpu_rmap_copy_neigh(rmap, cpu,
191 topology_sibling_cpumask(cpu), 1))
192 continue;
193 if (cpu_rmap_copy_neigh(rmap, cpu,
194 topology_core_cpumask(cpu), 2))
195 continue;
196 if (cpu_rmap_copy_neigh(rmap, cpu,
197 cpumask_of_node(cpu_to_node(cpu)), 3))
198 continue;
199 /* We could continue into NUMA node distances, but for now
200 * we give up.
201 */
202 }
203
204 debug_print_rmap(rmap, "after copying neighbours");
205
206 free_cpumask_var(update_mask);
207 return 0;
208 }
209 EXPORT_SYMBOL(cpu_rmap_update);
210
211 /* Glue between IRQ affinity notifiers and CPU rmaps */
212
213 struct irq_glue {
214 struct irq_affinity_notify notify;
215 struct cpu_rmap *rmap;
216 u16 index;
217 };
218
219 /**
220 * free_irq_cpu_rmap - free a CPU affinity reverse-map used for IRQs
221 * @rmap: Reverse-map allocated with alloc_irq_cpu_map(), or %NULL
222 *
223 * Must be called in process context, before freeing the IRQs.
224 */
free_irq_cpu_rmap(struct cpu_rmap * rmap)225 void free_irq_cpu_rmap(struct cpu_rmap *rmap)
226 {
227 struct irq_glue *glue;
228 u16 index;
229
230 if (!rmap)
231 return;
232
233 for (index = 0; index < rmap->used; index++) {
234 glue = rmap->obj[index];
235 irq_set_affinity_notifier(glue->notify.irq, NULL);
236 }
237
238 cpu_rmap_put(rmap);
239 }
240 EXPORT_SYMBOL(free_irq_cpu_rmap);
241
242 /**
243 * irq_cpu_rmap_notify - callback for IRQ subsystem when IRQ affinity updated
244 * @notify: struct irq_affinity_notify passed by irq/manage.c
245 * @mask: cpu mask for new SMP affinity
246 *
247 * This is executed in workqueue context.
248 */
249 static void
irq_cpu_rmap_notify(struct irq_affinity_notify * notify,const cpumask_t * mask)250 irq_cpu_rmap_notify(struct irq_affinity_notify *notify, const cpumask_t *mask)
251 {
252 struct irq_glue *glue =
253 container_of(notify, struct irq_glue, notify);
254 int rc;
255
256 rc = cpu_rmap_update(glue->rmap, glue->index, mask);
257 if (rc)
258 pr_warning("irq_cpu_rmap_notify: update failed: %d\n", rc);
259 }
260
261 /**
262 * irq_cpu_rmap_release - reclaiming callback for IRQ subsystem
263 * @ref: kref to struct irq_affinity_notify passed by irq/manage.c
264 */
irq_cpu_rmap_release(struct kref * ref)265 static void irq_cpu_rmap_release(struct kref *ref)
266 {
267 struct irq_glue *glue =
268 container_of(ref, struct irq_glue, notify.kref);
269
270 cpu_rmap_put(glue->rmap);
271 kfree(glue);
272 }
273
274 /**
275 * irq_cpu_rmap_add - add an IRQ to a CPU affinity reverse-map
276 * @rmap: The reverse-map
277 * @irq: The IRQ number
278 *
279 * This adds an IRQ affinity notifier that will update the reverse-map
280 * automatically.
281 *
282 * Must be called in process context, after the IRQ is allocated but
283 * before it is bound with request_irq().
284 */
irq_cpu_rmap_add(struct cpu_rmap * rmap,int irq)285 int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq)
286 {
287 struct irq_glue *glue = kzalloc(sizeof(*glue), GFP_KERNEL);
288 int rc;
289
290 if (!glue)
291 return -ENOMEM;
292 glue->notify.notify = irq_cpu_rmap_notify;
293 glue->notify.release = irq_cpu_rmap_release;
294 glue->rmap = rmap;
295 cpu_rmap_get(rmap);
296 glue->index = cpu_rmap_add(rmap, glue);
297 rc = irq_set_affinity_notifier(irq, &glue->notify);
298 if (rc) {
299 cpu_rmap_put(glue->rmap);
300 kfree(glue);
301 }
302 return rc;
303 }
304 EXPORT_SYMBOL(irq_cpu_rmap_add);
305