xref: /openbmc/linux/mm/percpu-km.c (revision eb3fcf00) 
1 /*
2  * mm/percpu-km.c - kernel memory based chunk allocation
3  *
4  * Copyright (C) 2010		SUSE Linux Products GmbH
5  * Copyright (C) 2010		Tejun Heo <tj@kernel.org>
6  *
7  * This file is released under the GPLv2.
8  *
9  * Chunks are allocated as a contiguous kernel memory using gfp
10  * allocation.  This is to be used on nommu architectures.
11  *
12  * To use percpu-km,
13  *
14  * - define CONFIG_NEED_PER_CPU_KM from the arch Kconfig.
15  *
16  * - CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK must not be defined.  It's
17  *   not compatible with PER_CPU_KM.  EMBED_FIRST_CHUNK should work
18  *   fine.
19  *
20  * - NUMA is not supported.  When setting up the first chunk,
21  *   @cpu_distance_fn should be NULL or report all CPUs to be nearer
22  *   than or at LOCAL_DISTANCE.
23  *
24  * - It's best if the chunk size is power of two multiple of
25  *   PAGE_SIZE.  Because each chunk is allocated as a contiguous
26  *   kernel memory block using alloc_pages(), memory will be wasted if
27  *   chunk size is not aligned.  percpu-km code will whine about it.
28  */
29 
30 #if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
31 #error "contiguous percpu allocation is incompatible with paged first chunk"
32 #endif
33 
34 #include <linux/log2.h>
35 
36 static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
37 			       int page_start, int page_end)
38 {
39 	return 0;
40 }
41 
42 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
43 				  int page_start, int page_end)
44 {
45 	/* nada */
46 }
47 
48 static struct pcpu_chunk *pcpu_create_chunk(void)
49 {
50 	const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
51 	struct pcpu_chunk *chunk;
52 	struct page *pages;
53 	int i;
54 
55 	chunk = pcpu_alloc_chunk();
56 	if (!chunk)
57 		return NULL;
58 
59 	pages = alloc_pages(GFP_KERNEL, 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) - pcpu_group_offsets[0];
70 
71 	spin_lock_irq(&pcpu_lock);
72 	pcpu_chunk_populated(chunk, 0, nr_pages);
73 	spin_unlock_irq(&pcpu_lock);
74 
75 	return chunk;
76 }
77 
78 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
79 {
80 	const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
81 
82 	if (chunk && chunk->data)
83 		__free_pages(chunk->data, order_base_2(nr_pages));
84 	pcpu_free_chunk(chunk);
85 }
86 
87 static struct page *pcpu_addr_to_page(void *addr)
88 {
89 	return virt_to_page(addr);
90 }
91 
92 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
93 {
94 	size_t nr_pages, alloc_pages;
95 
96 	/* all units must be in a single group */
97 	if (ai->nr_groups != 1) {
98 		printk(KERN_CRIT "percpu: can't handle more than one groups\n");
99 		return -EINVAL;
100 	}
101 
102 	nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT;
103 	alloc_pages = roundup_pow_of_two(nr_pages);
104 
105 	if (alloc_pages > nr_pages)
106 		printk(KERN_WARNING "percpu: wasting %zu pages per chunk\n",
107 		       alloc_pages - nr_pages);
108 
109 	return 0;
110 }
111