/* 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
 *
 * 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 *))

/*
 * Limit the maximum number of mmu_gather batches to reduce a risk of soft
 * lockups for non-preemptible kernels on huge machines when a lot of memory
 * is zapped during unmapping.
 * 10K pages freed at once should be safe even without a preemption point.
 */
#define MAX_GATHER_BATCH_COUNT  (10000UL/MAX_GATHER_BATCH)

/* 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;
        /* we are in the middle of an operation to clear
         * a full mm and can make some optimizations */
        unsigned int            fullmm : 1,
        /* we have performed an operation which
         * requires a complete flush of the tlb */
                                need_flush_all : 1;

        struct mmu_gather_batch *active;
        struct mmu_gather_batch local;
        struct page             *__pages[MMU_GATHER_BUNDLE];
        unsigned int            batch_count;
        /*
         * __tlb_adjust_range  will track the new addr here,
         * that that we can adjust the range after the flush
         */
        unsigned long addr;
        int page_size;
};

#define HAVE_GENERIC_MMU_GATHER

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

static inline void __tlb_adjust_range(struct mmu_gather *tlb,
                                      unsigned long address)
{
        tlb->start = min(tlb->start, address);
        tlb->end = max(tlb->end, address + PAGE_SIZE);
        /*
         * Track the last address with which we adjusted the range. This
         * will be used later to adjust again after a mmu_flush due to
         * failed __tlb_remove_page
         */
        tlb->addr = address;
}

static inline void __tlb_reset_range(struct mmu_gather *tlb)
{
        if (tlb->fullmm) {
                tlb->start = tlb->end = ~0;
        } else {
                tlb->start = TASK_SIZE;
                tlb->end = 0;
        }
}

static inline void tlb_remove_page_size(struct mmu_gather *tlb,
                                        struct page *page, int page_size)
{
        if (__tlb_remove_page_size(tlb, page, page_size)) {
                tlb_flush_mmu(tlb);
                tlb->page_size = page_size;
                __tlb_adjust_range(tlb, tlb->addr);
                __tlb_remove_page_size(tlb, page, page_size);
        }
}

static bool __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
{
        return __tlb_remove_page_size(tlb, page, PAGE_SIZE);
}

/* 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)
{
        return tlb_remove_page_size(tlb, page, PAGE_SIZE);
}

static inline bool __tlb_remove_pte_page(struct mmu_gather *tlb, struct page *page)
{
        /* active->nr should be zero when we call this */
        VM_BUG_ON_PAGE(tlb->active->nr, page);
        tlb->page_size = PAGE_SIZE;
        __tlb_adjust_range(tlb, tlb->addr);
        return __tlb_remove_page(tlb, page);
}

/*
 * In the case of tlb vma handling, we can optimise these away in the
 * case where we're doing a full MM flush.  When we're doing a munmap,
 * the vmas are adjusted to only cover the region to be torn down.
 */
#ifndef tlb_start_vma
#define tlb_start_vma(tlb, vma) do { } while (0)
#endif

#define __tlb_end_vma(tlb, vma)                                 \
        do {                                                    \
                if (!tlb->fullmm && tlb->end) {                 \
                        tlb_flush(tlb);                         \
                        __tlb_reset_range(tlb);                 \
                }                                               \
        } while (0)

#ifndef tlb_end_vma
#define tlb_end_vma     __tlb_end_vma
#endif

#ifndef __tlb_remove_tlb_entry
#define __tlb_remove_tlb_entry(tlb, ptep, address) do { } while (0)
#endif

/**
 * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
 *
 * Record the fact that pte's were really unmapped by updating the range,
 * so we can later optimise away the tlb invalidate.   This helps when
 * userspace is unmapping already-unmapped pages, which happens quite a lot.
 */
#define tlb_remove_tlb_entry(tlb, ptep, address)                \
        do {                                                    \
                __tlb_adjust_range(tlb, address);               \
                __tlb_remove_tlb_entry(tlb, ptep, address);     \
        } while (0)

/**
 * tlb_remove_pmd_tlb_entry - remember a pmd mapping for later tlb invalidation
 * This is a nop so far, because only x86 needs it.
 */
#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_adjust_range(tlb, address);               \
                __tlb_remove_pmd_tlb_entry(tlb, pmdp, address); \
        } while (0)

#define pte_free_tlb(tlb, ptep, address)                        \
        do {                                                    \
                __tlb_adjust_range(tlb, address);               \
                __pte_free_tlb(tlb, ptep, address);             \
        } while (0)

#ifndef __ARCH_HAS_4LEVEL_HACK
#define pud_free_tlb(tlb, pudp, address)                        \
        do {                                                    \
                __tlb_adjust_range(tlb, address);               \
                __pud_free_tlb(tlb, pudp, address);             \
        } while (0)
#endif

#define pmd_free_tlb(tlb, pmdp, address)                        \
        do {                                                    \
                __tlb_adjust_range(tlb, address);               \
                __pmd_free_tlb(tlb, pmdp, address);             \
        } while (0)

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

#endif /* _ASM_GENERIC__TLB_H */