kernel/irq/affinity.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2016 Thomas Gleixner.
 * Copyright (C) 2016-2017 Christoph Hellwig.
 */
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/cpu.h>
#include <linux/group_cpus.h>

static void default_calc_sets(struct irq_affinity *affd, unsigned int affvecs)
{
	affd->nr_sets = 1;
	affd->set_size[0] = affvecs;
}

/**
 * irq_create_affinity_masks - Create affinity masks for multiqueue spreading
 * @nvecs:	The total number of vectors
 * @affd:	Description of the affinity requirements
 *
 * Returns the irq_affinity_desc pointer or NULL if allocation failed.
 */
struct irq_affinity_desc *
irq_create_affinity_masks(unsigned int nvecs, struct irq_affinity *affd)
{
	unsigned int affvecs, curvec, usedvecs, i;
	struct irq_affinity_desc *masks = NULL;

	/*
	 * Determine the number of vectors which need interrupt affinities
	 * assigned. If the pre/post request exhausts the available vectors
	 * then nothing to do here except for invoking the calc_sets()
	 * callback so the device driver can adjust to the situation.
	 */
	if (nvecs > affd->pre_vectors + affd->post_vectors)
		affvecs = nvecs - affd->pre_vectors - affd->post_vectors;
	else
		affvecs = 0;

	/*
	 * Simple invocations do not provide a calc_sets() callback. Install
	 * the generic one.
	 */
	if (!affd->calc_sets)
		affd->calc_sets = default_calc_sets;

	/* Recalculate the sets */
	affd->calc_sets(affd, affvecs);

	if (WARN_ON_ONCE(affd->nr_sets > IRQ_AFFINITY_MAX_SETS))
		return NULL;

	/* Nothing to assign? */
	if (!affvecs)
		return NULL;

	masks = kzalloc_objs(*masks, nvecs);
	if (!masks)
		return NULL;

	/* Fill out vectors at the beginning that don't need affinity */
	for (curvec = 0; curvec < affd->pre_vectors; curvec++)
		cpumask_copy(&masks[curvec].mask, irq_default_affinity);

	/*
	 * Spread on present CPUs starting from affd->pre_vectors. If we
	 * have multiple sets, build each sets affinity mask separately.
	 */
	for (i = 0, usedvecs = 0; i < affd->nr_sets; i++) {
		unsigned int nr_masks, this_vecs = affd->set_size[i];
		struct cpumask *result = group_cpus_evenly(this_vecs, &nr_masks);

		if (!result) {
			kfree(masks);
			return NULL;
		}

		for (int j = 0; j < nr_masks; j++)
			cpumask_copy(&masks[curvec + j].mask, &result[j]);
		kfree(result);

		curvec += nr_masks;
		usedvecs += nr_masks;
	}

	/* Fill out vectors at the end that don't need affinity */
	if (usedvecs >= affvecs)
		curvec = affd->pre_vectors + affvecs;
	else
		curvec = affd->pre_vectors + usedvecs;
	for (; curvec < nvecs; curvec++)
		cpumask_copy(&masks[curvec].mask, irq_default_affinity);

	/* Mark the managed interrupts */
	for (i = affd->pre_vectors; i < nvecs - affd->post_vectors; i++)
		masks[i].is_managed = 1;

	return masks;
}

/**
 * irq_calc_affinity_vectors - Calculate the optimal number of vectors
 * @minvec:	The minimum number of vectors available
 * @maxvec:	The maximum number of vectors available
 * @affd:	Description of the affinity requirements
 */
unsigned int irq_calc_affinity_vectors(unsigned int minvec, unsigned int maxvec,
				       const struct irq_affinity *affd)
{
	unsigned int resv = affd->pre_vectors + affd->post_vectors;
	unsigned int set_vecs;

	if (resv > minvec)
		return 0;

	if (affd->calc_sets)
		set_vecs = maxvec - resv;
	else
		set_vecs = cpumask_weight(cpu_possible_mask);

	return resv + min(set_vecs, maxvec - resv);
}