1/*
  2 *  arch/arm/include/asm/tlb.h
  3 *
  4 *  Copyright (C) 2002 Russell King
  5 *
  6 * This program is free software; you can redistribute it and/or modify
  7 * it under the terms of the GNU General Public License version 2 as
  8 * published by the Free Software Foundation.
  9 *
 10 *  Experimentation shows that on a StrongARM, it appears to be faster
 11 *  to use the "invalidate whole tlb" rather than "invalidate single
 12 *  tlb" for this.
 13 *
 14 *  This appears true for both the process fork+exit case, as well as
 15 *  the munmap-large-area case.
 16 */
 17#ifndef __ASMARM_TLB_H
 18#define __ASMARM_TLB_H
 19
 20#include <asm/cacheflush.h>
 21
 22#ifndef CONFIG_MMU
 23
 24#include <linux/pagemap.h>
 25
 26#define tlb_flush(tlb)	((void) tlb)
 27
 28#include <asm-generic/tlb.h>
 29
 30#else /* !CONFIG_MMU */
 31
 32#include <linux/swap.h>
 33#include <asm/pgalloc.h>
 34#include <asm/tlbflush.h>
 35
 36/*
 37 * We need to delay page freeing for SMP as other CPUs can access pages
 38 * which have been removed but not yet had their TLB entries invalidated.
 39 * Also, as ARMv7 speculative prefetch can drag new entries into the TLB,
 40 * we need to apply this same delaying tactic to ensure correct operation.
 41 */
 42#if defined(CONFIG_SMP) || defined(CONFIG_CPU_32v7)
 43#define tlb_fast_mode(tlb)	0
 44#else
 45#define tlb_fast_mode(tlb)	1
 46#endif
 47
 48#define MMU_GATHER_BUNDLE	8
 49
 50/*
 51 * TLB handling.  This allows us to remove pages from the page
 52 * tables, and efficiently handle the TLB issues.
 53 */
 54struct mmu_gather {
 55	struct mm_struct	*mm;
 56	unsigned int		fullmm;
 57	struct vm_area_struct	*vma;
 58	unsigned long		range_start;
 59	unsigned long		range_end;
 60	unsigned int		nr;
 61	unsigned int		max;
 62	struct page		**pages;
 63	struct page		*local[MMU_GATHER_BUNDLE];
 64};
 65
 66DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
 67
 68/*
 69 * This is unnecessarily complex.  There's three ways the TLB shootdown
 70 * code is used:
 71 *  1. Unmapping a range of vmas.  See zap_page_range(), unmap_region().
 72 *     tlb->fullmm = 0, and tlb_start_vma/tlb_end_vma will be called.
 73 *     tlb->vma will be non-NULL.
 74 *  2. Unmapping all vmas.  See exit_mmap().
 75 *     tlb->fullmm = 1, and tlb_start_vma/tlb_end_vma will be called.
 76 *     tlb->vma will be non-NULL.  Additionally, page tables will be freed.
 77 *  3. Unmapping argument pages.  See shift_arg_pages().
 78 *     tlb->fullmm = 0, but tlb_start_vma/tlb_end_vma will not be called.
 79 *     tlb->vma will be NULL.
 80 */
 81static inline void tlb_flush(struct mmu_gather *tlb)
 82{
 83	if (tlb->fullmm || !tlb->vma)
 84		flush_tlb_mm(tlb->mm);
 85	else if (tlb->range_end > 0) {
 86		flush_tlb_range(tlb->vma, tlb->range_start, tlb->range_end);
 87		tlb->range_start = TASK_SIZE;
 88		tlb->range_end = 0;
 89	}
 90}
 91
 92static inline void tlb_add_flush(struct mmu_gather *tlb, unsigned long addr)
 93{
 94	if (!tlb->fullmm) {
 95		if (addr < tlb->range_start)
 96			tlb->range_start = addr;
 97		if (addr + PAGE_SIZE > tlb->range_end)
 98			tlb->range_end = addr + PAGE_SIZE;
 99	}
100}
101
102static inline void __tlb_alloc_page(struct mmu_gather *tlb)
103{
104	unsigned long addr = __get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
105
106	if (addr) {
107		tlb->pages = (void *)addr;
108		tlb->max = PAGE_SIZE / sizeof(struct page *);
109	}
110}
111
112static inline void tlb_flush_mmu(struct mmu_gather *tlb)
113{
114	tlb_flush(tlb);
115	if (!tlb_fast_mode(tlb)) {
116		free_pages_and_swap_cache(tlb->pages, tlb->nr);
117		tlb->nr = 0;
118		if (tlb->pages == tlb->local)
119			__tlb_alloc_page(tlb);
120	}
121}
122
123static inline void
124tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned int fullmm)
125{
126	tlb->mm = mm;
127	tlb->fullmm = fullmm;
128	tlb->vma = NULL;
129	tlb->max = ARRAY_SIZE(tlb->local);
130	tlb->pages = tlb->local;
131	tlb->nr = 0;
132	__tlb_alloc_page(tlb);
133}
134
135static inline void
136tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
137{
138	tlb_flush_mmu(tlb);
139
140	/* keep the page table cache within bounds */
141	check_pgt_cache();
142
143	if (tlb->pages != tlb->local)
144		free_pages((unsigned long)tlb->pages, 0);
145}
146
147/*
148 * Memorize the range for the TLB flush.
149 */
150static inline void
151tlb_remove_tlb_entry(struct mmu_gather *tlb, pte_t *ptep, unsigned long addr)
152{
153	tlb_add_flush(tlb, addr);
154}
155
156/*
157 * In the case of tlb vma handling, we can optimise these away in the
158 * case where we're doing a full MM flush.  When we're doing a munmap,
159 * the vmas are adjusted to only cover the region to be torn down.
160 */
161static inline void
162tlb_start_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
163{
164	if (!tlb->fullmm) {
165		flush_cache_range(vma, vma->vm_start, vma->vm_end);
166		tlb->vma = vma;
167		tlb->range_start = TASK_SIZE;
168		tlb->range_end = 0;
169	}
170}
171
172static inline void
173tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
174{
175	if (!tlb->fullmm)
176		tlb_flush(tlb);
177}
178
179static inline int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
180{
181	if (tlb_fast_mode(tlb)) {
182		free_page_and_swap_cache(page);
183		return 1; /* avoid calling tlb_flush_mmu */
184	}
185
186	tlb->pages[tlb->nr++] = page;
187	VM_BUG_ON(tlb->nr > tlb->max);
188	return tlb->max - tlb->nr;
189}
190
191static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
192{
193	if (!__tlb_remove_page(tlb, page))
194		tlb_flush_mmu(tlb);
195}
196
197static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte,
198	unsigned long addr)
199{
200	pgtable_page_dtor(pte);
201
202	/*
203	 * With the classic ARM MMU, a pte page has two corresponding pmd
204	 * entries, each covering 1MB.
205	 */
206	addr &= PMD_MASK;
207	tlb_add_flush(tlb, addr + SZ_1M - PAGE_SIZE);
208	tlb_add_flush(tlb, addr + SZ_1M);
209
210	tlb_remove_page(tlb, pte);
211}
212
213static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp,
214				  unsigned long addr)
215{
216#ifdef CONFIG_ARM_LPAE
217	tlb_add_flush(tlb, addr);
218	tlb_remove_page(tlb, virt_to_page(pmdp));
219#endif
220}
221
222#define pte_free_tlb(tlb, ptep, addr)	__pte_free_tlb(tlb, ptep, addr)
223#define pmd_free_tlb(tlb, pmdp, addr)	__pmd_free_tlb(tlb, pmdp, addr)
224#define pud_free_tlb(tlb, pudp, addr)	pud_free((tlb)->mm, pudp)
225
226#define tlb_migrate_finish(mm)		do { } while (0)
227
228#endif /* CONFIG_MMU */
229#endif