[linux.git] / lib / cpu_rmap.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * cpu_rmap.c: CPU affinity reverse-map support
 * Copyright 2011 Solarflare Communications Inc.
 */

#include <linux/cpu_rmap.h>
#include <linux/interrupt.h>
#include <linux/export.h>

/*
 * These functions maintain a mapping from CPUs to some ordered set of
 * objects with CPU affinities.  This can be seen as a reverse-map of
 * CPU affinity.  However, we do not assume that the object affinities
 * cover all CPUs in the system.  For those CPUs not directly covered
 * by object affinities, we attempt to find a nearest object based on
 * CPU topology.
 */

/**
 * alloc_cpu_rmap - allocate CPU affinity reverse-map
 * @size: Number of objects to be mapped
 * @flags: Allocation flags e.g. %GFP_KERNEL
 */
struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags)
{
	struct cpu_rmap *rmap;
	unsigned int cpu;
	size_t obj_offset;

	/* This is a silly number of objects, and we use u16 indices. */
	if (size > 0xffff)
		return NULL;

	/* Offset of object pointer array from base structure */
	obj_offset = ALIGN(offsetof(struct cpu_rmap, near[nr_cpu_ids]),
			   sizeof(void *));

	rmap = kzalloc(obj_offset + size * sizeof(rmap->obj[0]), flags);
	if (!rmap)
		return NULL;

	kref_init(&rmap->refcount);
	rmap->obj = (void **)((char *)rmap + obj_offset);

	/* Initially assign CPUs to objects on a rota, since we have
	 * no idea where the objects are.  Use infinite distance, so
	 * any object with known distance is preferable.  Include the
	 * CPUs that are not present/online, since we definitely want
	 * any newly-hotplugged CPUs to have some object assigned.
	 */
	for_each_possible_cpu(cpu) {
		rmap->near[cpu].index = cpu % size;
		rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
	}

	rmap->size = size;
	return rmap;
}
EXPORT_SYMBOL(alloc_cpu_rmap);

/**
 * cpu_rmap_release - internal reclaiming helper called from kref_put
 * @ref: kref to struct cpu_rmap
 */
static void cpu_rmap_release(struct kref *ref)
{
	struct cpu_rmap *rmap = container_of(ref, struct cpu_rmap, refcount);
	kfree(rmap);
}

/**
 * cpu_rmap_get - internal helper to get new ref on a cpu_rmap
 * @rmap: reverse-map allocated with alloc_cpu_rmap()
 */
static inline void cpu_rmap_get(struct cpu_rmap *rmap)
{
	kref_get(&rmap->refcount);
}

/**
 * cpu_rmap_put - release ref on a cpu_rmap
 * @rmap: reverse-map allocated with alloc_cpu_rmap()
 */
int cpu_rmap_put(struct cpu_rmap *rmap)
{
	return kref_put(&rmap->refcount, cpu_rmap_release);
}
EXPORT_SYMBOL(cpu_rmap_put);

/* Reevaluate nearest object for given CPU, comparing with the given
 * neighbours at the given distance.
 */
static bool cpu_rmap_copy_neigh(struct cpu_rmap *rmap, unsigned int cpu,
				const struct cpumask *mask, u16 dist)
{
	int neigh;

	for_each_cpu(neigh, mask) {
		if (rmap->near[cpu].dist > dist &&
		    rmap->near[neigh].dist <= dist) {
			rmap->near[cpu].index = rmap->near[neigh].index;
			rmap->near[cpu].dist = dist;
			return true;
		}
	}
	return false;
}

#ifdef DEBUG
static void debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
{
	unsigned index;
	unsigned int cpu;

	pr_info("cpu_rmap %p, %s:\n", rmap, prefix);

	for_each_possible_cpu(cpu) {
		index = rmap->near[cpu].index;
		pr_info("cpu %d -> obj %u (distance %u)\n",
			cpu, index, rmap->near[cpu].dist);
	}
}
#else
static inline void
debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
{
}
#endif

/**
 * cpu_rmap_add - add object to a rmap
 * @rmap: CPU rmap allocated with alloc_cpu_rmap()
 * @obj: Object to add to rmap
 *
 * Return index of object.
 */
int cpu_rmap_add(struct cpu_rmap *rmap, void *obj)
{
	u16 index;

	BUG_ON(rmap->used >= rmap->size);
	index = rmap->used++;
	rmap->obj[index] = obj;
	return index;
}
EXPORT_SYMBOL(cpu_rmap_add);

/**
 * cpu_rmap_update - update CPU rmap following a change of object affinity
 * @rmap: CPU rmap to update
 * @index: Index of object whose affinity changed
 * @affinity: New CPU affinity of object
 */
int cpu_rmap_update(struct cpu_rmap *rmap, u16 index,
		    const struct cpumask *affinity)
{
	cpumask_var_t update_mask;
	unsigned int cpu;

	if (unlikely(!zalloc_cpumask_var(&update_mask, GFP_KERNEL)))
		return -ENOMEM;

	/* Invalidate distance for all CPUs for which this used to be
	 * the nearest object.  Mark those CPUs for update.
	 */
	for_each_online_cpu(cpu) {
		if (rmap->near[cpu].index == index) {
			rmap->near[cpu].dist = CPU_RMAP_DIST_INF;
			cpumask_set_cpu(cpu, update_mask);
		}
	}

	debug_print_rmap(rmap, "after invalidating old distances");

	/* Set distance to 0 for all CPUs in the new affinity mask.
	 * Mark all CPUs within their NUMA nodes for update.
	 */
	for_each_cpu(cpu, affinity) {
		rmap->near[cpu].index = index;
		rmap->near[cpu].dist = 0;
		cpumask_or(update_mask, update_mask,
			   cpumask_of_node(cpu_to_node(cpu)));
	}

	debug_print_rmap(rmap, "after updating neighbours");

	/* Update distances based on topology */
	for_each_cpu(cpu, update_mask) {
		if (cpu_rmap_copy_neigh(rmap, cpu,
					topology_sibling_cpumask(cpu), 1))
			continue;
		if (cpu_rmap_copy_neigh(rmap, cpu,
					topology_core_cpumask(cpu), 2))
			continue;
		if (cpu_rmap_copy_neigh(rmap, cpu,
					cpumask_of_node(cpu_to_node(cpu)), 3))
			continue;
		/* We could continue into NUMA node distances, but for now
		 * we give up.
		 */
	}

	debug_print_rmap(rmap, "after copying neighbours");

	free_cpumask_var(update_mask);
	return 0;
}
EXPORT_SYMBOL(cpu_rmap_update);

/* Glue between IRQ affinity notifiers and CPU rmaps */

struct irq_glue {
	struct irq_affinity_notify notify;
	struct cpu_rmap *rmap;
	u16 index;
};

/**
 * free_irq_cpu_rmap - free a CPU affinity reverse-map used for IRQs
 * @rmap: Reverse-map allocated with alloc_irq_cpu_map(), or %NULL
 *
 * Must be called in process context, before freeing the IRQs.
 */
void free_irq_cpu_rmap(struct cpu_rmap *rmap)
{
	struct irq_glue *glue;
	u16 index;

	if (!rmap)
		return;

	for (index = 0; index < rmap->used; index++) {
		glue = rmap->obj[index];
		irq_set_affinity_notifier(glue->notify.irq, NULL);
	}

	cpu_rmap_put(rmap);
}
EXPORT_SYMBOL(free_irq_cpu_rmap);

/**
 * irq_cpu_rmap_notify - callback for IRQ subsystem when IRQ affinity updated
 * @notify: struct irq_affinity_notify passed by irq/manage.c
 * @mask: cpu mask for new SMP affinity
 *
 * This is executed in workqueue context.
 */
static void
irq_cpu_rmap_notify(struct irq_affinity_notify *notify, const cpumask_t *mask)
{
	struct irq_glue *glue =
		container_of(notify, struct irq_glue, notify);
	int rc;

	rc = cpu_rmap_update(glue->rmap, glue->index, mask);
	if (rc)
		pr_warn("irq_cpu_rmap_notify: update failed: %d\n", rc);
}

/**
 * irq_cpu_rmap_release - reclaiming callback for IRQ subsystem
 * @ref: kref to struct irq_affinity_notify passed by irq/manage.c
 */
static void irq_cpu_rmap_release(struct kref *ref)
{
	struct irq_glue *glue =
		container_of(ref, struct irq_glue, notify.kref);

	cpu_rmap_put(glue->rmap);
	kfree(glue);
}

/**
 * irq_cpu_rmap_add - add an IRQ to a CPU affinity reverse-map
 * @rmap: The reverse-map
 * @irq: The IRQ number
 *
 * This adds an IRQ affinity notifier that will update the reverse-map
 * automatically.
 *
 * Must be called in process context, after the IRQ is allocated but
 * before it is bound with request_irq().
 */
int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq)
{
	struct irq_glue *glue = kzalloc(sizeof(*glue), GFP_KERNEL);
	int rc;

	if (!glue)
		return -ENOMEM;
	glue->notify.notify = irq_cpu_rmap_notify;
	glue->notify.release = irq_cpu_rmap_release;
	glue->rmap = rmap;
	cpu_rmap_get(rmap);
	glue->index = cpu_rmap_add(rmap, glue);
	rc = irq_set_affinity_notifier(irq, &glue->notify);
	if (rc) {
		cpu_rmap_put(glue->rmap);
		kfree(glue);
	}
	return rc;
}
EXPORT_SYMBOL(irq_cpu_rmap_add);
Commit	Line	Data
d2912cb1	1	// SPDX-License-Identifier: GPL-2.0-only
c39649c3 BH	2	/*
	3	* cpu_rmap.c: CPU affinity reverse-map support
	4	* Copyright 2011 Solarflare Communications Inc.
c39649c3 BH	5	*/
	6
	7	#include <linux/cpu_rmap.h>
c39649c3	8	#include <linux/interrupt.h>
8bc3bcc9	9	#include <linux/export.h>
c39649c3 BH	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	*/
	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
896f97ea	43	kref_init(&rmap->refcount);
c39649c3 BH	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
896f97ea DD	62	/**
	63	* cpu_rmap_release - internal reclaiming helper called from kref_put
	64	* @ref: kref to struct cpu_rmap
	65	*/
	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	*/
	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	*/
	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
c39649c3 BH	91	/* Reevaluate nearest object for given CPU, comparing with the given
	92	* neighbours at the given distance.
	93	*/
	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
	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
	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	*/
	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	*/
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,
06931e62	191	topology_sibling_cpumask(cpu), 1))
c39649c3 BH	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
c39649c3 BH	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	*
896f97ea	223	* Must be called in process context, before freeing the IRQs.
c39649c3 BH	224	*/
	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	}
c39649c3	237
896f97ea	238	cpu_rmap_put(rmap);
c39649c3 BH	239	}
	240	EXPORT_SYMBOL(free_irq_cpu_rmap);
	241
896f97ea DD	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	*/
c39649c3 BH	249	static void
	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)
256339d6	258	pr_warn("irq_cpu_rmap_notify: update failed: %d\n", rc);
c39649c3 BH	259	}
c39649c3 BH	260
896f97ea DD	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	*/
c39649c3 BH	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);
896f97ea DD	269
896f97ea DD	270	cpu_rmap_put(glue->rmap);
c39649c3 BH	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	*/
	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;
896f97ea	295	cpu_rmap_get(rmap);
c39649c3 BH	296	glue->index = cpu_rmap_add(rmap, glue);
c39649c3 BH	297	rc = irq_set_affinity_notifier(irq, &glue->notify);
896f97ea DD	298	if (rc) {
896f97ea DD	299	cpu_rmap_put(glue->rmap);
c39649c3	300	kfree(glue);
896f97ea	301	}
c39649c3 BH	302	return rc;
	303	}
	304	EXPORT_SYMBOL(irq_cpu_rmap_add);