text: /* 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.
   *
   * 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/config.h>
  #include <linux/swap.h>
  #include <asm/pgalloc.h>
  #include <asm/tlbflush.h>
  
  /*
   * For UP we don't need to worry about TLB flush
   * and page free order so much..
   */
  #ifdef CONFIG_SMP
    #ifdef ARCH_FREE_PTR_NR
      #define FREE_PTR_NR   ARCH_FREE_PTR_NR
    #else
      #define FREE_PTE_NR	506
    #endif
    #define tlb_fast_mode(tlb) ((tlb)->nr == ~0U)
  #else
    #define FREE_PTE_NR	1
    #define tlb_fast_mode(tlb) 1
  #endif
  
  /* 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;
  	unsigned int		nr;	/* set to ~0U means fast mode */
  	unsigned int		need_flush;/* Really unmapped some ptes? */
  	unsigned int		fullmm; /* non-zero means full mm flush */
  	struct page *		pages[FREE_PTE_NR];
  };
  
  /* Users of the generic TLB shootdown code must declare this storage space. */
  DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
  
  /* tlb_gather_mmu
   *	Return a pointer to an initialized struct mmu_gather.
   */
  static inline struct mmu_gather *
  tlb_gather_mmu(struct mm_struct *mm, unsigned int full_mm_flush)
  {
  	struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);
  
  	tlb->mm = mm;
  
  	/* Use fast mode if only one CPU is online */
  	tlb->nr = num_online_cpus() > 1 ? 0U : ~0U;
  
  	tlb->fullmm = full_mm_flush;
  
  	return tlb;
  }
  
  static inline void
  tlb_flush_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
  {
  	if (!tlb->need_flush)
  		return;
  	tlb->need_flush = 0;
  	tlb_flush(tlb);
  	if (!tlb_fast_mode(tlb)) {
  		free_pages_and_swap_cache(tlb->pages, tlb->nr);
  		tlb->nr = 0;
  	}
  }
  
  /* tlb_finish_mmu
   *	Called at the end of the shootdown operation to free up any resources
   *	that were required.
   */
  static inline void
  tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
  {
  	tlb_flush_mmu(tlb, start, end);
  
  	/* keep the page table cache within bounds */
  	check_pgt_cache();
  
  	put_cpu_var(mmu_gathers);
  }
  
  /* tlb_remove_page
   *	Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while
   *	handling the additional races in SMP caused by other CPUs caching valid
   *	mappings in their TLBs.
   */
  static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
  {
  	tlb->need_flush = 1;
  	if (tlb_fast_mode(tlb)) {
  		free_page_and_swap_cache(page);
  		return;
  	}
  	tlb->pages[tlb->nr++] = page;
  	if (tlb->nr >= FREE_PTE_NR)
  		tlb_flush_mmu(tlb, 0, 0);
  }
  
  /**
   * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
   *
   * Record the fact that pte's were really umapped in ->need_flush, 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->need_flush = 1;				\
  		__tlb_remove_tlb_entry(tlb, ptep, address);	\
  	} while (0)
  
  #define pte_free_tlb(tlb, ptep)					\
  	do {							\
  		tlb->need_flush = 1;				\
  		__pte_free_tlb(tlb, ptep);			\
  	} while (0)
  
  #ifndef __ARCH_HAS_4LEVEL_HACK
  #define pud_free_tlb(tlb, pudp)					\
  	do {							\
  		tlb->need_flush = 1;				\
  		__pud_free_tlb(tlb, pudp);			\
  	} while (0)
  #endif
  
  #define pmd_free_tlb(tlb, pmdp)					\
  	do {							\
  		tlb->need_flush = 1;				\
  		__pmd_free_tlb(tlb, pmdp);			\
  	} while (0)
  
  #define tlb_migrate_finish(mm) do {} while (0)
  
  #endif /* _ASM_GENERIC__TLB_H */
  