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 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 41 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, 42 int page_start, int page_end) 43 { 44 /* nada */ 45 } 46 47 static struct pcpu_chunk *pcpu_create_chunk(enum pcpu_chunk_type type, 48 gfp_t gfp) 49 { 50 const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT; 51 struct pcpu_chunk *chunk; 52 struct page *pages; 53 unsigned long flags; 54 int i; 55 56 chunk = pcpu_alloc_chunk(type, gfp); 57 if (!chunk) 58 return NULL; 59 60 pages = alloc_pages(gfp, order_base_2(nr_pages)); 61 if (!pages) { 62 pcpu_free_chunk(chunk); 63 return NULL; 64 } 65 66 for (i = 0; i < nr_pages; i++) 67 pcpu_set_page_chunk(nth_page(pages, i), chunk); 68 69 chunk->data = pages; 70 chunk->base_addr = page_address(pages); 71 72 spin_lock_irqsave(&pcpu_lock, flags); 73 pcpu_chunk_populated(chunk, 0, nr_pages); 74 spin_unlock_irqrestore(&pcpu_lock, flags); 75 76 pcpu_stats_chunk_alloc(); 77 trace_percpu_create_chunk(chunk->base_addr); 78 79 return chunk; 80 } 81 82 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk) 83 { 84 const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT; 85 86 if (!chunk) 87 return; 88 89 pcpu_stats_chunk_dealloc(); 90 trace_percpu_destroy_chunk(chunk->base_addr); 91 92 if (chunk->data) 93 __free_pages(chunk->data, order_base_2(nr_pages)); 94 pcpu_free_chunk(chunk); 95 } 96 97 static struct page *pcpu_addr_to_page(void *addr) 98 { 99 return virt_to_page(addr); 100 } 101 102 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai) 103 { 104 size_t nr_pages, alloc_pages; 105 106 /* all units must be in a single group */ 107 if (ai->nr_groups != 1) { 108 pr_crit("can't handle more than one group\n"); 109 return -EINVAL; 110 } 111 112 nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT; 113 alloc_pages = roundup_pow_of_two(nr_pages); 114 115 if (alloc_pages > nr_pages) 116 pr_warn("wasting %zu pages per chunk\n", 117 alloc_pages - nr_pages); 118 119 return 0; 120 } 121