blob: 065ee6bfa82a2463ee60c790f08c5b60382715f3 [file] [log] [blame]
Vineet Gupta45890f62015-03-09 18:53:49 +05301/*
2 * Copyright (C) 2015 Synopsys, Inc. (www.synopsys.com)
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 *
8 */
9
10#include <linux/bootmem.h>
11#include <linux/export.h>
12#include <linux/highmem.h>
13#include <asm/processor.h>
14#include <asm/pgtable.h>
15#include <asm/pgalloc.h>
16#include <asm/tlbflush.h>
17
18/*
19 * HIGHMEM API:
20 *
21 * kmap() API provides sleep semantics hence refered to as "permanent maps"
22 * It allows mapping LAST_PKMAP pages, using @last_pkmap_nr as the cursor
23 * for book-keeping
24 *
25 * kmap_atomic() can't sleep (calls pagefault_disable()), thus it provides
26 * shortlived ala "temporary mappings" which historically were implemented as
27 * fixmaps (compile time addr etc). Their book-keeping is done per cpu.
28 *
29 * Both these facts combined (preemption disabled and per-cpu allocation)
30 * means the total number of concurrent fixmaps will be limited to max
31 * such allocations in a single control path. Thus KM_TYPE_NR (another
32 * historic relic) is a small'ish number which caps max percpu fixmaps
33 *
34 * ARC HIGHMEM Details
35 *
36 * - the kernel vaddr space from 0x7z to 0x8z (currently used by vmalloc/module)
37 * is now shared between vmalloc and kmap (non overlapping though)
38 *
39 * - Both fixmap/pkmap use a dedicated page table each, hooked up to swapper PGD
40 * This means each only has 1 PGDIR_SIZE worth of kvaddr mappings, which means
41 * 2M of kvaddr space for typical config (8K page and 11:8:13 traversal split)
42 *
43 * - fixmap anyhow needs a limited number of mappings. So 2M kvaddr == 256 PTE
44 * slots across NR_CPUS would be more than sufficient (generic code defines
45 * KM_TYPE_NR as 20).
46 *
47 * - pkmap being preemptible, in theory could do with more than 256 concurrent
48 * mappings. However, generic pkmap code: map_new_virtual(), doesn't traverse
49 * the PGD and only works with a single page table @pkmap_page_table, hence
50 * sets the limit
51 */
52
53extern pte_t * pkmap_page_table;
54static pte_t * fixmap_page_table;
55
56void *kmap(struct page *page)
57{
58 BUG_ON(in_interrupt());
59 if (!PageHighMem(page))
60 return page_address(page);
61
62 return kmap_high(page);
63}
64
65void *kmap_atomic(struct page *page)
66{
67 int idx, cpu_idx;
68 unsigned long vaddr;
69
70 preempt_disable();
71 pagefault_disable();
72 if (!PageHighMem(page))
73 return page_address(page);
74
75 cpu_idx = kmap_atomic_idx_push();
76 idx = cpu_idx + KM_TYPE_NR * smp_processor_id();
77 vaddr = FIXMAP_ADDR(idx);
78
79 set_pte_at(&init_mm, vaddr, fixmap_page_table + idx,
80 mk_pte(page, kmap_prot));
81
82 return (void *)vaddr;
83}
84EXPORT_SYMBOL(kmap_atomic);
85
86void __kunmap_atomic(void *kv)
87{
88 unsigned long kvaddr = (unsigned long)kv;
89
90 if (kvaddr >= FIXMAP_BASE && kvaddr < (FIXMAP_BASE + FIXMAP_SIZE)) {
91
92 /*
93 * Because preemption is disabled, this vaddr can be associated
94 * with the current allocated index.
95 * But in case of multiple live kmap_atomic(), it still relies on
96 * callers to unmap in right order.
97 */
98 int cpu_idx = kmap_atomic_idx();
99 int idx = cpu_idx + KM_TYPE_NR * smp_processor_id();
100
101 WARN_ON(kvaddr != FIXMAP_ADDR(idx));
102
103 pte_clear(&init_mm, kvaddr, fixmap_page_table + idx);
104 local_flush_tlb_kernel_range(kvaddr, kvaddr + PAGE_SIZE);
105
106 kmap_atomic_idx_pop();
107 }
108
109 pagefault_enable();
110 preempt_enable();
111}
112EXPORT_SYMBOL(__kunmap_atomic);
113
114noinline pte_t *alloc_kmap_pgtable(unsigned long kvaddr)
115{
116 pgd_t *pgd_k;
117 pud_t *pud_k;
118 pmd_t *pmd_k;
119 pte_t *pte_k;
120
121 pgd_k = pgd_offset_k(kvaddr);
122 pud_k = pud_offset(pgd_k, kvaddr);
123 pmd_k = pmd_offset(pud_k, kvaddr);
124
125 pte_k = (pte_t *)alloc_bootmem_low_pages(PAGE_SIZE);
126 pmd_populate_kernel(&init_mm, pmd_k, pte_k);
127 return pte_k;
128}
129
130void kmap_init(void)
131{
132 /* Due to recursive include hell, we can't do this in processor.h */
133 BUILD_BUG_ON(PAGE_OFFSET < (VMALLOC_END + FIXMAP_SIZE + PKMAP_SIZE));
134
135 BUILD_BUG_ON(KM_TYPE_NR > PTRS_PER_PTE);
136 pkmap_page_table = alloc_kmap_pgtable(PKMAP_BASE);
137
138 BUILD_BUG_ON(LAST_PKMAP > PTRS_PER_PTE);
139 fixmap_page_table = alloc_kmap_pgtable(FIXMAP_BASE);
140}