1/* include/asm-generic/tlb.h
  2 *
  3 *	Generic TLB shootdown code
  4 *
  5 * Copyright 2001 Red Hat, Inc.
  6 * Based on code from mm/memory.c Copyright Linus Torvalds and others.
  7 *
  8 * Copyright 2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
  9 *
 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.
 14 */
 15#ifndef _ASM_GENERIC__TLB_H
 16#define _ASM_GENERIC__TLB_H
 17
 18#include <linux/swap.h>
 19#include <asm/pgalloc.h>
 20#include <asm/tlbflush.h>
 21
 22#ifdef CONFIG_HAVE_RCU_TABLE_FREE
 23/*
 24 * Semi RCU freeing of the page directories.
 25 *
 26 * This is needed by some architectures to implement software pagetable walkers.
 27 *
 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
 31 * the walk.
 32 *
 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
 36 * freed page.
 37 *
 38 * Architectures that do not have this (PPC) need to delay the freeing by some
 39 * other means, this is that means.
 40 *
 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.
 44 *
 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().
 49 *
 50 */
 51struct mmu_table_batch {
 52	struct rcu_head		rcu;
 53	unsigned int		nr;
 54	void			*tables[0];
 55};
 56
 57#define MAX_TABLE_BATCH		\
 58	((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))
 59
 60extern void tlb_table_flush(struct mmu_gather *tlb);
 61extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
 62
 63#endif
 64
 65/*
 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.
 68 */
 69#define MMU_GATHER_BUNDLE	8
 70
 71struct mmu_gather_batch {
 72	struct mmu_gather_batch	*next;
 73	unsigned int		nr;
 74	unsigned int		max;
 75	struct page		*pages[0];
 76};
 77
 78#define MAX_GATHER_BATCH	\
 79	((PAGE_SIZE - sizeof(struct mmu_gather_batch)) / sizeof(void *))
 80
 81/* struct mmu_gather is an opaque type used by the mm code for passing around
 82 * any data needed by arch specific code for tlb_remove_page.
 83 */
 84struct mmu_gather {
 85	struct mm_struct	*mm;
 86#ifdef CONFIG_HAVE_RCU_TABLE_FREE
 87	struct mmu_table_batch	*batch;
 88#endif
 89	unsigned int		need_flush : 1,	/* Did free PTEs */
 90				fast_mode  : 1; /* No batching   */
 91
 92	unsigned int		fullmm;
 93
 94	struct mmu_gather_batch *active;
 95	struct mmu_gather_batch	local;
 96	struct page		*__pages[MMU_GATHER_BUNDLE];
 97};
 98
 99#define HAVE_GENERIC_MMU_GATHER
100
101static inline int tlb_fast_mode(struct mmu_gather *tlb)
102{
103#ifdef CONFIG_SMP
104	return tlb->fast_mode;
105#else
106	/*
107	 * For UP we don't need to worry about TLB flush
108	 * and page free order so much..
109	 */
110	return 1;
111#endif
112}
113
114void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm);
115void tlb_flush_mmu(struct mmu_gather *tlb);
116void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end);
117int __tlb_remove_page(struct mmu_gather *tlb, struct page *page);
118
119/* tlb_remove_page
120 *	Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when
121 *	required.
122 */
123static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
124{
125	if (!__tlb_remove_page(tlb, page))
126		tlb_flush_mmu(tlb);
127}
128
129/**
130 * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
131 *
132 * Record the fact that pte's were really umapped in ->need_flush, so we can
133 * later optimise away the tlb invalidate.   This helps when userspace is
134 * unmapping already-unmapped pages, which happens quite a lot.
135 */
136#define tlb_remove_tlb_entry(tlb, ptep, address)		\
137	do {							\
138		tlb->need_flush = 1;				\
139		__tlb_remove_tlb_entry(tlb, ptep, address);	\
140	} while (0)
141
142/**
143 * tlb_remove_pmd_tlb_entry - remember a pmd mapping for later tlb invalidation
144 * This is a nop so far, because only x86 needs it.
145 */
146#ifndef __tlb_remove_pmd_tlb_entry
147#define __tlb_remove_pmd_tlb_entry(tlb, pmdp, address) do {} while (0)
148#endif
149
150#define tlb_remove_pmd_tlb_entry(tlb, pmdp, address)		\
151	do {							\
152		tlb->need_flush = 1;				\
153		__tlb_remove_pmd_tlb_entry(tlb, pmdp, address);	\
154	} while (0)
155
156#define pte_free_tlb(tlb, ptep, address)			\
157	do {							\
158		tlb->need_flush = 1;				\
159		__pte_free_tlb(tlb, ptep, address);		\
160	} while (0)
161
162#ifndef __ARCH_HAS_4LEVEL_HACK
163#define pud_free_tlb(tlb, pudp, address)			\
164	do {							\
165		tlb->need_flush = 1;				\
166		__pud_free_tlb(tlb, pudp, address);		\
167	} while (0)
168#endif
169
170#define pmd_free_tlb(tlb, pmdp, address)			\
171	do {							\
172		tlb->need_flush = 1;				\
173		__pmd_free_tlb(tlb, pmdp, address);		\
174	} while (0)
175
176#define tlb_migrate_finish(mm) do {} while (0)
177
178#endif /* _ASM_GENERIC__TLB_H */