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 /* 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_gather_mmu_fullmm() / 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_fullmm() 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_FLUSH_CACHE
  *
  *  Indicates the architecture has flush_cache_range() but it needs *NOT* be called
  *  before unmapping a VMA.
  *
  *  NOTE: strictly speaking we shouldn't have this knob and instead rely on
  *    flush_cache_range() being a NOP, except Sparc64 seems to be
  *    different here.
  *
  *  MMU_GATHER_MERGE_VMAS
  *
  *  Indicates the architecture wants to merge ranges over VMAs; typical when
  *  multiple range invalidates are more expensive than a full invalidate.
  *
  *  MMU_GATHER_NO_RANGE
  *
  *  Use this if your architecture lacks an efficient flush_tlb_range(). This
  *  option implies MMU_GATHER_MERGE_VMAS above.
  *
  *  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[];
 };
 
 #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[];
 };
 
 #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        vma_pfn  : 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)
 #error MMU_GATHER_NO_RANGE relies on default tlb_flush()
 #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);
 }
 
 #else /* CONFIG_MMU_GATHER_NO_RANGE */
 
 #ifndef tlb_flush
 /*
  * 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);
     }
 }
 #endif
 
 #endif /* CONFIG_MMU_GATHER_NO_RANGE */
 
 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);
     tlb->vma_pfn  = !!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP));
 }
 
 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.
  */
 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);
 #ifndef CONFIG_MMU_GATHER_NO_FLUSH_CACHE
     flush_cache_range(vma, vma->vm_start, vma->vm_end);
 #endif
 }
 
 static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
 {
     if (tlb->fullmm)
         return;
 
     /*
      * VM_PFNMAP is more fragile because the core mm will not track the
      * page mapcount -- there might not be page-frames for these PFNs after
      * all. Force flush TLBs for such ranges to avoid munmap() vs
      * unmap_mapping_range() races.
      */
     if (tlb->vma_pfn || !IS_ENABLED(CONFIG_MMU_GATHER_MERGE_VMAS)) {
         /*
          * Do a TLB flush and reset the range at VMA boundaries; this avoids
          * the ranges growing with the unused space between consecutive VMAs.
          */
         tlb_flush_mmu_tlbonly(tlb);
     }
 }
 
 /*
  * 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 >= P4D_SIZE)                \
             tlb_flush_p4d_range(tlb, address, _sz); \
         else if (_sz >= PUD_SIZE)           \
             tlb_flush_pud_range(tlb, address, _sz); \
         else if (_sz >= PMD_SIZE)           \
             tlb_flush_pmd_range(tlb, address, _sz); \
         else                        \
             tlb_flush_pte_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
 
 #ifndef pte_needs_flush
 static inline bool pte_needs_flush(pte_t oldpte, pte_t newpte)
 {
     return true;
 }
 #endif
 
 #ifndef huge_pmd_needs_flush
 static inline bool huge_pmd_needs_flush(pmd_t oldpmd, pmd_t newpmd)
 {
     return true;
 }
 #endif
 
 #endif /* CONFIG_MMU */
 
 #endif /* _ASM_GENERIC__TLB_H */

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