tlb.h

Go to the documentation of this file.

/* include/asm-generic/tlb.h
 *
 *  Generic TLB shootdown code
 *
 * Copyright 2001 Red Hat, Inc.
 * Based on code from mm/memory.c Copyright Linus Torvalds and others.
 *
 * Copyright 2011 Red Hat, Inc., Peter Zijlstra <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */
#ifndef _ASM_GENERIC__TLB_H
#define _ASM_GENERIC__TLB_H

#include <linux/swap.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>

#ifdef CONFIG_HAVE_RCU_TABLE_FREE
/*
 * Semi RCU freeing of the page directories.
 *
 * This is needed by some architectures to implement software pagetable walkers.
 *
 * gup_fast() and other software pagetable walkers do a lockless page-table
 * walk and therefore needs some synchronization with the freeing of the page
 * directories. The chosen means to accomplish that is by disabling IRQs over
 * the walk.
 *
 * Architectures that use IPIs to flush TLBs will then automagically DTRT,
 * since we unlink the page, flush TLBs, free the page. Since the disabling of
 * IRQs delays the completion of the TLB flush we can never observe an already
 * freed page.
 *
 * Architectures that do not have this (PPC) need to delay the freeing by some
 * other means, this is that means.
 *
 * What we do is batch the freed directory pages (tables) and RCU free them.
 * We use the sched RCU variant, as that guarantees that IRQ/preempt disabling
 * holds off grace periods.
 *
 * However, in order to batch these pages we need to allocate storage, this
 * allocation is deep inside the MM code and can thus easily fail on memory
 * pressure. To guarantee progress we fall back to single table freeing, see
 * the implementation of tlb_remove_table_one().
 *
 */
struct mmu_table_batch {
    struct rcu_head     rcu;
    unsigned int        nr;
    void            *tables[0];
};

#define MAX_TABLE_BATCH     \
    ((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))

extern void tlb_table_flush(struct mmu_gather *tlb);
extern void tlb_remove_table(struct mmu_gather *tlb, void *table);

#endif

/*
 * If we can't allocate a page to make a big batch of page pointers
 * to work on, then just handle a few from the on-stack structure.
 */
#define MMU_GATHER_BUNDLE   8

struct mmu_gather_batch {
    struct mmu_gather_batch *next;
    unsigned int        nr;
    unsigned int        max;
    struct page     *pages[0];
};

#define MAX_GATHER_BATCH    \
    ((PAGE_SIZE - sizeof(struct mmu_gather_batch)) / sizeof(void *))

/* struct mmu_gather is an opaque type used by the mm code for passing around
 * any data needed by arch specific code for tlb_remove_page.
 */
struct mmu_gather {
    struct mm_struct    *mm;
#ifdef CONFIG_HAVE_RCU_TABLE_FREE
    struct mmu_table_batch  *batch;
#endif
    unsigned long       start;
    unsigned long       end;
    unsigned int        need_flush : 1, /* Did free PTEs */
                fast_mode  : 1; /* No batching   */

    unsigned int        fullmm;

    struct mmu_gather_batch *active;
    struct mmu_gather_batch local;
    struct page     *__pages[MMU_GATHER_BUNDLE];
};

#define HAVE_GENERIC_MMU_GATHER

static inline int tlb_fast_mode(struct mmu_gather *tlb)
{
#ifdef CONFIG_SMP
    return tlb->fast_mode;
#else
    /*
     * For UP we don't need to worry about TLB flush
     * and page free order so much..
     */
    return 1;
#endif
}

void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm);
void tlb_flush_mmu(struct mmu_gather *tlb);
void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start,
                            unsigned long end);
int __tlb_remove_page(struct mmu_gather *tlb, struct page *page);

/* tlb_remove_page
 *  Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when
 *  required.
 */
static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
{
    if (!__tlb_remove_page(tlb, page))
        tlb_flush_mmu(tlb);
}

#define tlb_remove_tlb_entry(tlb, ptep, address)        \
    do {                            \
        tlb->need_flush = 1;                \
        __tlb_remove_tlb_entry(tlb, ptep, address); \
    } while (0)

#ifndef __tlb_remove_pmd_tlb_entry
#define __tlb_remove_pmd_tlb_entry(tlb, pmdp, address) do {} while (0)
#endif

#define tlb_remove_pmd_tlb_entry(tlb, pmdp, address)        \
    do {                            \
        tlb->need_flush = 1;                \
        __tlb_remove_pmd_tlb_entry(tlb, pmdp, address); \
    } while (0)

#define pte_free_tlb(tlb, ptep, address)            \
    do {                            \
        tlb->need_flush = 1;                \
        __pte_free_tlb(tlb, ptep, address);     \
    } while (0)

#ifndef __ARCH_HAS_4LEVEL_HACK
#define pud_free_tlb(tlb, pudp, address)            \
    do {                            \
        tlb->need_flush = 1;                \
        __pud_free_tlb(tlb, pudp, address);     \
    } while (0)
#endif

#define pmd_free_tlb(tlb, pmdp, address)            \
    do {                            \
        tlb->need_flush = 1;                \
        __pmd_free_tlb(tlb, pmdp, address);     \
    } while (0)

#define tlb_migrate_finish(mm) do {} while (0)

#endif /* _ASM_GENERIC__TLB_H */