1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2016 Thomas Gleixner.
4  * Copyright (C) 2016-2017 Christoph Hellwig.
5  */
6 #include <linux/interrupt.h>
7 #include <linux/kernel.h>
8 #include <linux/slab.h>
9 #include <linux/cpu.h>
10 #include <linux/group_cpus.h>
11 
default_calc_sets(struct irq_affinity * affd,unsigned int affvecs)12 static void default_calc_sets(struct irq_affinity *affd, unsigned int affvecs)
13 {
14 	affd->nr_sets = 1;
15 	affd->set_size[0] = affvecs;
16 }
17 
18 /**
19  * irq_create_affinity_masks - Create affinity masks for multiqueue spreading
20  * @nvecs:	The total number of vectors
21  * @affd:	Description of the affinity requirements
22  *
23  * Returns the irq_affinity_desc pointer or NULL if allocation failed.
24  */
25 struct irq_affinity_desc *
irq_create_affinity_masks(unsigned int nvecs,struct irq_affinity * affd)26 irq_create_affinity_masks(unsigned int nvecs, struct irq_affinity *affd)
27 {
28 	unsigned int affvecs, curvec, usedvecs, i;
29 	struct irq_affinity_desc *masks = NULL;
30 
31 	/*
32 	 * Determine the number of vectors which need interrupt affinities
33 	 * assigned. If the pre/post request exhausts the available vectors
34 	 * then nothing to do here except for invoking the calc_sets()
35 	 * callback so the device driver can adjust to the situation.
36 	 */
37 	if (nvecs > affd->pre_vectors + affd->post_vectors)
38 		affvecs = nvecs - affd->pre_vectors - affd->post_vectors;
39 	else
40 		affvecs = 0;
41 
42 	/*
43 	 * Simple invocations do not provide a calc_sets() callback. Install
44 	 * the generic one.
45 	 */
46 	if (!affd->calc_sets)
47 		affd->calc_sets = default_calc_sets;
48 
49 	/* Recalculate the sets */
50 	affd->calc_sets(affd, affvecs);
51 
52 	if (WARN_ON_ONCE(affd->nr_sets > IRQ_AFFINITY_MAX_SETS))
53 		return NULL;
54 
55 	/* Nothing to assign? */
56 	if (!affvecs)
57 		return NULL;
58 
59 	masks = kcalloc(nvecs, sizeof(*masks), GFP_KERNEL);
60 	if (!masks)
61 		return NULL;
62 
63 	/* Fill out vectors at the beginning that don't need affinity */
64 	for (curvec = 0; curvec < affd->pre_vectors; curvec++)
65 		cpumask_copy(&masks[curvec].mask, irq_default_affinity);
66 
67 	/*
68 	 * Spread on present CPUs starting from affd->pre_vectors. If we
69 	 * have multiple sets, build each sets affinity mask separately.
70 	 */
71 	for (i = 0, usedvecs = 0; i < affd->nr_sets; i++) {
72 		unsigned int this_vecs = affd->set_size[i];
73 		int j;
74 		struct cpumask *result = group_cpus_evenly(this_vecs);
75 
76 		if (!result) {
77 			kfree(masks);
78 			return NULL;
79 		}
80 
81 		for (j = 0; j < this_vecs; j++)
82 			cpumask_copy(&masks[curvec + j].mask, &result[j]);
83 		kfree(result);
84 
85 		curvec += this_vecs;
86 		usedvecs += this_vecs;
87 	}
88 
89 	/* Fill out vectors at the end that don't need affinity */
90 	if (usedvecs >= affvecs)
91 		curvec = affd->pre_vectors + affvecs;
92 	else
93 		curvec = affd->pre_vectors + usedvecs;
94 	for (; curvec < nvecs; curvec++)
95 		cpumask_copy(&masks[curvec].mask, irq_default_affinity);
96 
97 	/* Mark the managed interrupts */
98 	for (i = affd->pre_vectors; i < nvecs - affd->post_vectors; i++)
99 		masks[i].is_managed = 1;
100 
101 	return masks;
102 }
103 
104 /**
105  * irq_calc_affinity_vectors - Calculate the optimal number of vectors
106  * @minvec:	The minimum number of vectors available
107  * @maxvec:	The maximum number of vectors available
108  * @affd:	Description of the affinity requirements
109  */
irq_calc_affinity_vectors(unsigned int minvec,unsigned int maxvec,const struct irq_affinity * affd)110 unsigned int irq_calc_affinity_vectors(unsigned int minvec, unsigned int maxvec,
111 				       const struct irq_affinity *affd)
112 {
113 	unsigned int resv = affd->pre_vectors + affd->post_vectors;
114 	unsigned int set_vecs;
115 
116 	if (resv > minvec)
117 		return 0;
118 
119 	if (affd->calc_sets) {
120 		set_vecs = maxvec - resv;
121 	} else {
122 		cpus_read_lock();
123 		set_vecs = cpumask_weight(cpu_possible_mask);
124 		cpus_read_unlock();
125 	}
126 
127 	return resv + min(set_vecs, maxvec - resv);
128 }
129