/* 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 */
