1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * mm/percpu-km.c - kernel memory based chunk allocation
4 *
5 * Copyright (C) 2010 SUSE Linux Products GmbH
6 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
7 *
8 * Chunks are allocated as a contiguous kernel memory using gfp
9 * allocation. This is to be used on nommu architectures.
10 *
11 * To use percpu-km,
12 *
13 * - define CONFIG_NEED_PER_CPU_KM from the arch Kconfig.
14 *
15 * - CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK must not be defined. It's
16 * not compatible with PER_CPU_KM. EMBED_FIRST_CHUNK should work
17 * fine.
18 *
19 * - NUMA is not supported. When setting up the first chunk,
20 * @cpu_distance_fn should be NULL or report all CPUs to be nearer
21 * than or at LOCAL_DISTANCE.
22 *
23 * - It's best if the chunk size is power of two multiple of
24 * PAGE_SIZE. Because each chunk is allocated as a contiguous
25 * kernel memory block using alloc_pages(), memory will be wasted if
26 * chunk size is not aligned. percpu-km code will whine about it.
27 */
28
29 #if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
30 #error "contiguous percpu allocation is incompatible with paged first chunk"
31 #endif
32
33 #include <linux/log2.h>
34
pcpu_populate_chunk(struct pcpu_chunk * chunk,int page_start,int page_end,gfp_t gfp)35 static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
36 int page_start, int page_end, gfp_t gfp)
37 {
38 return 0;
39 }
40
pcpu_depopulate_chunk(struct pcpu_chunk * chunk,int page_start,int page_end)41 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
42 int page_start, int page_end)
43 {
44 /* nada */
45 }
46
pcpu_create_chunk(gfp_t gfp)47 static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp)
48 {
49 const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
50 struct pcpu_chunk *chunk;
51 struct page *pages;
52 unsigned long flags;
53 int i;
54
55 chunk = pcpu_alloc_chunk(gfp);
56 if (!chunk)
57 return NULL;
58
59 pages = alloc_pages(gfp, order_base_2(nr_pages));
60 if (!pages) {
61 pcpu_free_chunk(chunk);
62 return NULL;
63 }
64
65 for (i = 0; i < nr_pages; i++)
66 pcpu_set_page_chunk(nth_page(pages, i), chunk);
67
68 chunk->data = pages;
69 chunk->base_addr = page_address(pages);
70
71 spin_lock_irqsave(&pcpu_lock, flags);
72 pcpu_chunk_populated(chunk, 0, nr_pages);
73 spin_unlock_irqrestore(&pcpu_lock, flags);
74
75 pcpu_stats_chunk_alloc();
76 trace_percpu_create_chunk(chunk->base_addr);
77
78 return chunk;
79 }
80
pcpu_destroy_chunk(struct pcpu_chunk * chunk)81 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
82 {
83 const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
84
85 if (!chunk)
86 return;
87
88 pcpu_stats_chunk_dealloc();
89 trace_percpu_destroy_chunk(chunk->base_addr);
90
91 if (chunk->data)
92 __free_pages(chunk->data, order_base_2(nr_pages));
93 pcpu_free_chunk(chunk);
94 }
95
pcpu_addr_to_page(void * addr)96 static struct page *pcpu_addr_to_page(void *addr)
97 {
98 return virt_to_page(addr);
99 }
100
pcpu_verify_alloc_info(const struct pcpu_alloc_info * ai)101 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
102 {
103 size_t nr_pages, alloc_pages;
104
105 /* all units must be in a single group */
106 if (ai->nr_groups != 1) {
107 pr_crit("can't handle more than one group\n");
108 return -EINVAL;
109 }
110
111 nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT;
112 alloc_pages = roundup_pow_of_two(nr_pages);
113
114 if (alloc_pages > nr_pages)
115 pr_warn("wasting %zu pages per chunk\n",
116 alloc_pages - nr_pages);
117
118 return 0;
119 }
120