1 /* include/asm-generic/tlb.h
3 * Generic TLB shootdown code
5 * Copyright 2001 Red Hat, Inc.
6 * Based on code from mm/memory.c Copyright Linus Torvalds and others.
8 * Copyright 2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public License
12 * as published by the Free Software Foundation; either version
13 * 2 of the License, or (at your option) any later version.
15 #ifndef _ASM_GENERIC__TLB_H
16 #define _ASM_GENERIC__TLB_H
18 #include <linux/swap.h>
19 #include <asm/pgalloc.h>
20 #include <asm/tlbflush.h>
22 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
24 * Semi RCU freeing of the page directories.
26 * This is needed by some architectures to implement software pagetable walkers.
28 * gup_fast() and other software pagetable walkers do a lockless page-table
29 * walk and therefore needs some synchronization with the freeing of the page
30 * directories. The chosen means to accomplish that is by disabling IRQs over
33 * Architectures that use IPIs to flush TLBs will then automagically DTRT,
34 * since we unlink the page, flush TLBs, free the page. Since the disabling of
35 * IRQs delays the completion of the TLB flush we can never observe an already
38 * Architectures that do not have this (PPC) need to delay the freeing by some
39 * other means, this is that means.
41 * What we do is batch the freed directory pages (tables) and RCU free them.
42 * We use the sched RCU variant, as that guarantees that IRQ/preempt disabling
43 * holds off grace periods.
45 * However, in order to batch these pages we need to allocate storage, this
46 * allocation is deep inside the MM code and can thus easily fail on memory
47 * pressure. To guarantee progress we fall back to single table freeing, see
48 * the implementation of tlb_remove_table_one().
51 struct mmu_table_batch {
57 #define MAX_TABLE_BATCH \
58 ((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))
60 extern void tlb_table_flush(struct mmu_gather *tlb);
61 extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
66 * If we can't allocate a page to make a big batch of page pointers
67 * to work on, then just handle a few from the on-stack structure.
69 #define MMU_GATHER_BUNDLE 8
71 struct mmu_gather_batch {
72 struct mmu_gather_batch *next;
75 struct page *pages[0];
78 #define MAX_GATHER_BATCH \
79 ((PAGE_SIZE - sizeof(struct mmu_gather_batch)) / sizeof(void *))
82 * Limit the maximum number of mmu_gather batches to reduce a risk of soft
83 * lockups for non-preemptible kernels on huge machines when a lot of memory
84 * is zapped during unmapping.
85 * 10K pages freed at once should be safe even without a preemption point.
87 #define MAX_GATHER_BATCH_COUNT (10000UL/MAX_GATHER_BATCH)
89 /* struct mmu_gather is an opaque type used by the mm code for passing around
90 * any data needed by arch specific code for tlb_remove_page.
94 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
95 struct mmu_table_batch *batch;
97 unsigned int need_flush : 1, /* Did free PTEs */
98 fast_mode : 1; /* No batching */
102 struct mmu_gather_batch *active;
103 struct mmu_gather_batch local;
104 struct page *__pages[MMU_GATHER_BUNDLE];
105 unsigned int batch_count;
108 #define HAVE_GENERIC_MMU_GATHER
110 static inline int tlb_fast_mode(struct mmu_gather *tlb)
113 return tlb->fast_mode;
116 * For UP we don't need to worry about TLB flush
117 * and page free order so much..
123 void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm);
124 void tlb_flush_mmu(struct mmu_gather *tlb);
125 void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end);
126 int __tlb_remove_page(struct mmu_gather *tlb, struct page *page);
129 * Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when
132 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
134 if (!__tlb_remove_page(tlb, page))
139 * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
141 * Record the fact that pte's were really umapped in ->need_flush, so we can
142 * later optimise away the tlb invalidate. This helps when userspace is
143 * unmapping already-unmapped pages, which happens quite a lot.
145 #define tlb_remove_tlb_entry(tlb, ptep, address) \
147 tlb->need_flush = 1; \
148 __tlb_remove_tlb_entry(tlb, ptep, address); \
151 #define pte_free_tlb(tlb, ptep, address) \
153 tlb->need_flush = 1; \
154 __pte_free_tlb(tlb, ptep, address); \
157 #ifndef __ARCH_HAS_4LEVEL_HACK
158 #define pud_free_tlb(tlb, pudp, address) \
160 tlb->need_flush = 1; \
161 __pud_free_tlb(tlb, pudp, address); \
165 #define pmd_free_tlb(tlb, pmdp, address) \
167 tlb->need_flush = 1; \
168 __pmd_free_tlb(tlb, pmdp, address); \
171 #define tlb_migrate_finish(mm) do {} while (0)
173 #endif /* _ASM_GENERIC__TLB_H */