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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
+
+void tlb_remove_table_sync_one(void);
+
+#else
+
+#ifdef tlb_needs_table_invalidate
+#error tlb_needs_table_invalidate() requires MMU_GATHER_RCU_TABLE_FREE
+#endif
+
+static inline void tlb_remove_table_sync_one(void) { }
+
+#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 */