/* SPDX-License-Identifier: GPL-2.0-or-later */

  /* 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

   */
  #ifndef _ASM_GENERIC__TLB_H
  #define _ASM_GENERIC__TLB_H

  #include <linux/mmu_notifier.h>

  #include <linux/swap.h>

  #include <linux/hugetlb_inline.h>

  #include <asm/tlbflush.h>

  #include <asm/cacheflush.h>

  /*
   * Blindly accessing user memory from NMI context can be dangerous
   * if we're in the middle of switching the current user task or switching
   * the loaded mm.
   */
  #ifndef nmi_uaccess_okay
  # define nmi_uaccess_okay() true
  #endif

  #ifdef CONFIG_MMU

  /*
   * Generic MMU-gather implementation.
   *
   * The mmu_gather data structure is used by the mm code to implement the
   * correct and efficient ordering of freeing pages and TLB invalidations.
   *
   * This correct ordering is:
   *
   *  1) unhook page
   *  2) TLB invalidate page
   *  3) free page
   *
   * That is, we must never free a page before we have ensured there are no live
   * translations left to it. Otherwise it might be possible to observe (or
   * worse, change) the page content after it has been reused.
   *
   * The mmu_gather API consists of:
   *
   *  - tlb_gather_mmu() / tlb_finish_mmu(); start and finish a mmu_gather
   *
   *    Finish in particular will issue a (final) TLB invalidate and free
   *    all (remaining) queued pages.
   *
   *  - tlb_start_vma() / tlb_end_vma(); marks the start / end of a VMA
   *
   *    Defaults to flushing at tlb_end_vma() to reset the range; helps when
   *    there's large holes between the VMAs.
   *

   *  - tlb_remove_table()
   *
   *    tlb_remove_table() is the basic primitive to free page-table directories
   *    (__p*_free_tlb()).  In it's most primitive form it is an alias for
   *    tlb_remove_page() below, for when page directories are pages and have no
   *    additional constraints.
   *
   *    See also MMU_GATHER_TABLE_FREE and MMU_GATHER_RCU_TABLE_FREE.
   *

   *  - tlb_remove_page() / __tlb_remove_page()
   *  - tlb_remove_page_size() / __tlb_remove_page_size()
   *
   *    __tlb_remove_page_size() is the basic primitive that queues a page for
   *    freeing. __tlb_remove_page() assumes PAGE_SIZE. Both will return a
   *    boolean indicating if the queue is (now) full and a call to
   *    tlb_flush_mmu() is required.
   *
   *    tlb_remove_page() and tlb_remove_page_size() imply the call to
   *    tlb_flush_mmu() when required and has no return value.
   *

   *  - tlb_change_page_size()

   *
   *    call before __tlb_remove_page*() to set the current page-size; implies a
   *    possible tlb_flush_mmu() call.
   *

   *  - tlb_flush_mmu() / tlb_flush_mmu_tlbonly()

   *
   *    tlb_flush_mmu_tlbonly() - does the TLB invalidate (and resets
   *                              related state, like the range)
   *

   *    tlb_flush_mmu() - in addition to the above TLB invalidate, also frees
   *			whatever pages are still batched.

   *
   *  - mmu_gather::fullmm
   *
   *    A flag set by tlb_gather_mmu() to indicate we're going to free
   *    the entire mm; this allows a number of optimizations.
   *
   *    - We can ignore tlb_{start,end}_vma(); because we don't
   *      care about ranges. Everything will be shot down.
   *
   *    - (RISC) architectures that use ASIDs can cycle to a new ASID
   *      and delay the invalidation until ASID space runs out.
   *
   *  - mmu_gather::need_flush_all
   *
   *    A flag that can be set by the arch code if it wants to force
   *    flush the entire TLB irrespective of the range. For instance
   *    x86-PAE needs this when changing top-level entries.
   *

   * And allows the architecture to provide and implement tlb_flush():

   *
   * tlb_flush() may, in addition to the above mentioned mmu_gather fields, make
   * use of:
   *
   *  - mmu_gather::start / mmu_gather::end
   *
   *    which provides the range that needs to be flushed to cover the pages to
   *    be freed.
   *
   *  - mmu_gather::freed_tables
   *
   *    set when we freed page table pages
   *
   *  - tlb_get_unmap_shift() / tlb_get_unmap_size()
   *

   *    returns the smallest TLB entry size unmapped in this range.
   *
   * If an architecture does not provide tlb_flush() a default implementation

   * based on flush_tlb_range() will be used, unless MMU_GATHER_NO_RANGE is
   * specified, in which case we'll default to flush_tlb_mm().

   *
   * Additionally there are a few opt-in features:
   *

   *  MMU_GATHER_PAGE_SIZE

   *
   *  This ensures we call tlb_flush() every time tlb_change_page_size() actually
   *  changes the size and provides mmu_gather::page_size to tlb_flush().
   *

   *  This might be useful if your architecture has size specific TLB
   *  invalidation instructions.
   *

   *  MMU_GATHER_TABLE_FREE

   *
   *  This provides tlb_remove_table(), to be used instead of tlb_remove_page()

   *  for page directores (__p*_free_tlb()).
   *
   *  Useful if your architecture has non-page page directories.

   *
   *  When used, an architecture is expected to provide __tlb_remove_table()
   *  which does the actual freeing of these pages.
   *

   *  MMU_GATHER_RCU_TABLE_FREE
   *
   *  Like MMU_GATHER_TABLE_FREE, and adds semi-RCU semantics to the free (see
   *  comment below).
   *
   *  Useful if your architecture doesn't use IPIs for remote TLB invalidates
   *  and therefore doesn't naturally serialize with software page-table walkers.
   *

   *  MMU_GATHER_NO_RANGE
   *
   *  Use this if your architecture lacks an efficient flush_tlb_range().

   *
   *  MMU_GATHER_NO_GATHER
   *
   *  If the option is set the mmu_gather will not track individual pages for
   *  delayed page free anymore. A platform that enables the option needs to
   *  provide its own implementation of the __tlb_remove_page_size() function to
   *  free pages.
   *
   *  This is useful if your architecture already flushes TLB entries in the
   *  various ptep_get_and_clear() functions.

   */

  #ifdef CONFIG_MMU_GATHER_TABLE_FREE

  struct mmu_table_batch {

  #ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE

  	struct rcu_head		rcu;

  #endif

  	unsigned int		nr;
  	void			*tables[0];
  };
  
  #define MAX_TABLE_BATCH		\
  	((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))

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

  #else /* !CONFIG_MMU_GATHER_HAVE_TABLE_FREE */
  
  /*
   * Without MMU_GATHER_TABLE_FREE the architecture is assumed to have page based
   * page directories and we can use the normal page batching to free them.
   */
  #define tlb_remove_table(tlb, page) tlb_remove_page((tlb), (page))
  
  #endif /* CONFIG_MMU_GATHER_TABLE_FREE */
  
  #ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE

  /*
   * This allows an architecture that does not use the linux page-tables for
   * hardware to skip the TLBI when freeing page tables.
   */
  #ifndef tlb_needs_table_invalidate
  #define tlb_needs_table_invalidate() (true)

  #endif

  #else
  
  #ifdef tlb_needs_table_invalidate

  #error tlb_needs_table_invalidate() requires MMU_GATHER_RCU_TABLE_FREE

  #endif

  #endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */

  #ifndef CONFIG_MMU_GATHER_NO_GATHER

  /*
   * 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)

  extern bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page,
  				   int page_size);
  #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;

  #ifdef CONFIG_MMU_GATHER_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
  	 */
  	unsigned int		need_flush_all : 1;
  
  	/*
  	 * we have removed page directories
  	 */
  	unsigned int		freed_tables : 1;

  	/*
  	 * at which levels have we cleared entries?
  	 */
  	unsigned int		cleared_ptes : 1;
  	unsigned int		cleared_pmds : 1;
  	unsigned int		cleared_puds : 1;
  	unsigned int		cleared_p4ds : 1;

  	/*
  	 * tracks VM_EXEC | VM_HUGETLB in tlb_start_vma
  	 */
  	unsigned int		vma_exec : 1;
  	unsigned int		vma_huge : 1;

  	unsigned int		batch_count;

  #ifndef CONFIG_MMU_GATHER_NO_GATHER

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

  #ifdef CONFIG_MMU_GATHER_PAGE_SIZE

  	unsigned int page_size;
  #endif

  #endif

  };

  void tlb_flush_mmu(struct mmu_gather *tlb);

  static inline void __tlb_adjust_range(struct mmu_gather *tlb,

  				      unsigned long address,
  				      unsigned int range_size)

  {
  	tlb->start = min(tlb->start, address);

  	tlb->end = max(tlb->end, address + range_size);

  }
  
  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;
  	}

  	tlb->freed_tables = 0;

  	tlb->cleared_ptes = 0;
  	tlb->cleared_pmds = 0;
  	tlb->cleared_puds = 0;
  	tlb->cleared_p4ds = 0;

  	/*
  	 * Do not reset mmu_gather::vma_* fields here, we do not
  	 * call into tlb_start_vma() again to set them if there is an
  	 * intermediate flush.
  	 */
  }

  #ifdef CONFIG_MMU_GATHER_NO_RANGE
  
  #if defined(tlb_flush) || defined(tlb_start_vma) || defined(tlb_end_vma)
  #error MMU_GATHER_NO_RANGE relies on default tlb_flush(), tlb_start_vma() and tlb_end_vma()
  #endif
  
  /*
   * When an architecture does not have efficient means of range flushing TLBs
   * there is no point in doing intermediate flushes on tlb_end_vma() to keep the
   * range small. We equally don't have to worry about page granularity or other
   * things.
   *
   * All we need to do is issue a full flush for any !0 range.
   */
  static inline void tlb_flush(struct mmu_gather *tlb)
  {
  	if (tlb->end)
  		flush_tlb_mm(tlb->mm);
  }
  
  static inline void
  tlb_update_vma_flags(struct mmu_gather *tlb, struct vm_area_struct *vma) { }
  
  #define tlb_end_vma tlb_end_vma
  static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma) { }
  
  #else /* CONFIG_MMU_GATHER_NO_RANGE */

  #ifndef tlb_flush
  
  #if defined(tlb_start_vma) || defined(tlb_end_vma)
  #error Default tlb_flush() relies on default tlb_start_vma() and tlb_end_vma()
  #endif

  /*
   * When an architecture does not provide its own tlb_flush() implementation
   * but does have a reasonably efficient flush_vma_range() implementation
   * use that.
   */

  static inline void tlb_flush(struct mmu_gather *tlb)
  {
  	if (tlb->fullmm || tlb->need_flush_all) {
  		flush_tlb_mm(tlb->mm);
  	} else if (tlb->end) {
  		struct vm_area_struct vma = {
  			.vm_mm = tlb->mm,
  			.vm_flags = (tlb->vma_exec ? VM_EXEC    : 0) |
  				    (tlb->vma_huge ? VM_HUGETLB : 0),
  		};
  
  		flush_tlb_range(&vma, tlb->start, tlb->end);
  	}
  }
  
  static inline void
  tlb_update_vma_flags(struct mmu_gather *tlb, struct vm_area_struct *vma)
  {
  	/*
  	 * flush_tlb_range() implementations that look at VM_HUGETLB (tile,
  	 * mips-4k) flush only large pages.
  	 *
  	 * flush_tlb_range() implementations that flush I-TLB also flush D-TLB
  	 * (tile, xtensa, arm), so it's ok to just add VM_EXEC to an existing
  	 * range.
  	 *
  	 * We rely on tlb_end_vma() to issue a flush, such that when we reset
  	 * these values the batch is empty.
  	 */

  	tlb->vma_huge = is_vm_hugetlb_page(vma);

  	tlb->vma_exec = !!(vma->vm_flags & VM_EXEC);

  }

  #else
  
  static inline void
  tlb_update_vma_flags(struct mmu_gather *tlb, struct vm_area_struct *vma) { }
  
  #endif

  #endif /* CONFIG_MMU_GATHER_NO_RANGE */

  static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
  {

  	/*
  	 * Anything calling __tlb_adjust_range() also sets at least one of
  	 * these bits.
  	 */
  	if (!(tlb->freed_tables || tlb->cleared_ptes || tlb->cleared_pmds ||
  	      tlb->cleared_puds || tlb->cleared_p4ds))

  		return;
  
  	tlb_flush(tlb);
  	mmu_notifier_invalidate_range(tlb->mm, tlb->start, tlb->end);
  	__tlb_reset_range(tlb);
  }

  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);

  }

  static inline 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 void tlb_change_page_size(struct mmu_gather *tlb,

  						     unsigned int page_size)
  {

  #ifdef CONFIG_MMU_GATHER_PAGE_SIZE

  	if (tlb->page_size && tlb->page_size != page_size) {

  		if (!tlb->fullmm && !tlb->need_flush_all)

  			tlb_flush_mmu(tlb);
  	}

  	tlb->page_size = page_size;
  #endif
  }

  static inline unsigned long tlb_get_unmap_shift(struct mmu_gather *tlb)
  {
  	if (tlb->cleared_ptes)
  		return PAGE_SHIFT;
  	if (tlb->cleared_pmds)
  		return PMD_SHIFT;
  	if (tlb->cleared_puds)
  		return PUD_SHIFT;
  	if (tlb->cleared_p4ds)
  		return P4D_SHIFT;
  
  	return PAGE_SHIFT;
  }
  
  static inline unsigned long tlb_get_unmap_size(struct mmu_gather *tlb)
  {
  	return 1UL << tlb_get_unmap_shift(tlb);
  }

  /*
   * 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

  static inline void tlb_start_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
  {
  	if (tlb->fullmm)
  		return;
  
  	tlb_update_vma_flags(tlb, vma);
  	flush_cache_range(vma, vma->vm_start, vma->vm_end);
  }

  #endif

  #ifndef tlb_end_vma

  static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
  {
  	if (tlb->fullmm)
  		return;
  
  	/*
  	 * Do a TLB flush and reset the range at VMA boundaries; this avoids
  	 * the ranges growing with the unused space between consecutive VMAs,
  	 * but also the mmu_gather::vma_* flags from tlb_start_vma() rely on
  	 * this.
  	 */
  	tlb_flush_mmu_tlbonly(tlb);
  }

  #endif

  /*
   * tlb_flush_{pte|pmd|pud|p4d}_range() adjust the tlb->start and tlb->end,
   * and set corresponding cleared_*.
   */
  static inline void tlb_flush_pte_range(struct mmu_gather *tlb,
  				     unsigned long address, unsigned long size)
  {
  	__tlb_adjust_range(tlb, address, size);
  	tlb->cleared_ptes = 1;
  }
  
  static inline void tlb_flush_pmd_range(struct mmu_gather *tlb,
  				     unsigned long address, unsigned long size)
  {
  	__tlb_adjust_range(tlb, address, size);
  	tlb->cleared_pmds = 1;
  }
  
  static inline void tlb_flush_pud_range(struct mmu_gather *tlb,
  				     unsigned long address, unsigned long size)
  {
  	__tlb_adjust_range(tlb, address, size);
  	tlb->cleared_puds = 1;
  }
  
  static inline void tlb_flush_p4d_range(struct mmu_gather *tlb,
  				     unsigned long address, unsigned long size)
  {
  	__tlb_adjust_range(tlb, address, size);
  	tlb->cleared_p4ds = 1;
  }

  #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_flush_pte_range(tlb, address, PAGE_SIZE);	\

  		__tlb_remove_tlb_entry(tlb, ptep, address);	\
  	} while (0)

  #define tlb_remove_huge_tlb_entry(h, tlb, ptep, address)	\
  	do {							\
  		unsigned long _sz = huge_page_size(h);		\

  		if (_sz == PMD_SIZE)				\

  			tlb_flush_pmd_range(tlb, address, _sz);	\

  		else if (_sz == PUD_SIZE)			\

  			tlb_flush_pud_range(tlb, address, _sz);	\

  		__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_flush_pmd_range(tlb, address, HPAGE_PMD_SIZE);	\

  		__tlb_remove_pmd_tlb_entry(tlb, pmdp, address);		\

  	} while (0)

  /**
   * tlb_remove_pud_tlb_entry - remember a pud mapping for later tlb
   * invalidation. This is a nop so far, because only x86 needs it.
   */
  #ifndef __tlb_remove_pud_tlb_entry
  #define __tlb_remove_pud_tlb_entry(tlb, pudp, address) do {} while (0)
  #endif
  
  #define tlb_remove_pud_tlb_entry(tlb, pudp, address)			\
  	do {								\

  		tlb_flush_pud_range(tlb, address, HPAGE_PUD_SIZE);	\

  		__tlb_remove_pud_tlb_entry(tlb, pudp, address);		\
  	} while (0)

  /*
   * For things like page tables caches (ie caching addresses "inside" the
   * page tables, like x86 does), for legacy reasons, flushing an
   * individual page had better flush the page table caches behind it. This
   * is definitely how x86 works, for example. And if you have an
   * architected non-legacy page table cache (which I'm not aware of
   * anybody actually doing), you're going to have some architecturally
   * explicit flushing for that, likely *separate* from a regular TLB entry
   * flush, and thus you'd need more than just some range expansion..
   *
   * So if we ever find an architecture
   * that would want something that odd, I think it is up to that
   * architecture to do its own odd thing, not cause pain for others
   * http://lkml.kernel.org/r/CA+55aFzBggoXtNXQeng5d_mRoDnaMBE5Y+URs+PHR67nUpMtaw@mail.gmail.com
   *
   * For now w.r.t page table cache, mark the range_size as PAGE_SIZE
   */

  #ifndef pte_free_tlb

  #define pte_free_tlb(tlb, ptep, address)			\

  	do {							\

  		tlb_flush_pmd_range(tlb, address, PAGE_SIZE);	\

  		tlb->freed_tables = 1;				\

  		__pte_free_tlb(tlb, ptep, address);		\

  	} while (0)

  #endif

  #ifndef pmd_free_tlb

  #define pmd_free_tlb(tlb, pmdp, address)			\
  	do {							\

  		tlb_flush_pud_range(tlb, address, PAGE_SIZE);	\

  		tlb->freed_tables = 1;				\

  		__pmd_free_tlb(tlb, pmdp, address);		\
  	} while (0)

  #endif

  #ifndef pud_free_tlb

  #define pud_free_tlb(tlb, pudp, address)			\

  	do {							\

  		tlb_flush_p4d_range(tlb, address, PAGE_SIZE);	\

  		tlb->freed_tables = 1;				\

  		__pud_free_tlb(tlb, pudp, address);		\

  	} while (0)
  #endif

  #ifndef p4d_free_tlb

  #define p4d_free_tlb(tlb, pudp, address)			\

  	do {							\

  		__tlb_adjust_range(tlb, address, PAGE_SIZE);	\

  		tlb->freed_tables = 1;				\

  		__p4d_free_tlb(tlb, pudp, address);		\

  	} while (0)

  #endif

  #endif /* CONFIG_MMU */

  #endif /* _ASM_GENERIC__TLB_H */