cregit-Linux how code gets into the kernel

Release 4.12 include/asm-generic/tlb.h

/* 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
 * 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.


#include <linux/swap.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>

 * Semi RCU freeing of the page directories.
 * This is needed by some architectures to implement software pagetable walkers.
 * gup_fast() and other software pagetable walkers do a lockless page-table
 * walk and therefore needs some synchronization with the freeing of the page
 * directories. The chosen means to accomplish that is by disabling IRQs over
 * the walk.
 * Architectures that use IPIs to flush TLBs will then automagically DTRT,
 * since we unlink the page, flush TLBs, free the page. Since the disabling of
 * IRQs delays the completion of the TLB flush we can never observe an already
 * freed page.
 * Architectures that do not have this (PPC) need to delay the freeing by some
 * other means, this is that means.
 * What we do is batch the freed directory pages (tables) and RCU free them.
 * We use the sched RCU variant, as that guarantees that IRQ/preempt disabling
 * holds off grace periods.
 * However, in order to batch these pages we need to allocate storage, this
 * allocation is deep inside the MM code and can thus easily fail on memory
 * pressure. To guarantee progress we fall back to single table freeing, see
 * the implementation of tlb_remove_table_one().

struct mmu_table_batch {
struct rcu_head		rcu;
unsigned int		nr;
void			*tables[0];

#define MAX_TABLE_BATCH		\
	((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))

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


 * 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.


struct mmu_gather_batch {
struct mmu_gather_batch	*next;
unsigned int		nr;
unsigned int		max;
struct page		*pages[0];

	((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.


/* 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;
struct mmu_table_batch	*batch;
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 */
need_flush_all : 1;

struct mmu_gather_batch *active;
struct mmu_gather_batch	local;
struct page		*__pages[MMU_GATHER_BUNDLE];
unsigned int		batch_count;
int page_size;


void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start, unsigned long end);
void tlb_flush_mmu(struct mmu_gather *tlb);
void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start,
							unsigned long end);
extern bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page,
				   int page_size);

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); }


Will Deacon4389.58%150.00%
Aneesh Kumar K.V510.42%150.00%

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; } }


Will Deacon46100.00%2100.00%

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); }


Aneesh Kumar K.V36100.00%2100.00%

static inline bool __tlb_remove_page(struct mmu_gather *tlb, struct page *page) { return __tlb_remove_page_size(tlb, page, PAGE_SIZE); }


Aneesh Kumar K.V27100.00%2100.00%

/* 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); }


Aneesh Kumar K.V27100.00%1100.00%

#ifndef tlb_remove_check_page_size_change #define tlb_remove_check_page_size_change tlb_remove_check_page_size_change
static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb, unsigned int page_size) { /* * We don't care about page size change, just update * mmu_gather page size here so that debug checks * doesn't throw false warning. */ #ifdef CONFIG_DEBUG_VM tlb->page_size = page_size; #endif }


Aneesh Kumar K.V28100.00%1100.00%

#endif /* * 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 #define tlb_start_vma(tlb, vma) do { } while (0) #endif #define __tlb_end_vma(tlb, vma) \ do { \ if (!tlb->fullmm && tlb->end) { \ tlb_flush(tlb); \ __tlb_reset_range(tlb); \ } \ } while (0) #ifndef tlb_end_vma #define tlb_end_vma __tlb_end_vma #endif #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_adjust_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 { \ __tlb_adjust_range(tlb, address, huge_page_size(h)); \ __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_adjust_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_adjust_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 * * * For now w.r.t page table cache, mark the range_size as PAGE_SIZE */ #define pte_free_tlb(tlb, ptep, address) \ do { \ __tlb_adjust_range(tlb, address, PAGE_SIZE); \ __pte_free_tlb(tlb, ptep, address); \ } while (0) #define pmd_free_tlb(tlb, pmdp, address) \ do { \ __tlb_adjust_range(tlb, address, PAGE_SIZE); \ __pmd_free_tlb(tlb, pmdp, address); \ } while (0) #ifndef __ARCH_HAS_4LEVEL_HACK #define pud_free_tlb(tlb, pudp, address) \ do { \ __tlb_adjust_range(tlb, address, PAGE_SIZE); \ __pud_free_tlb(tlb, pudp, address); \ } while (0) #endif #ifndef __ARCH_HAS_5LEVEL_HACK #define p4d_free_tlb(tlb, pudp, address) \ do { \ __tlb_adjust_range(tlb, address, PAGE_SIZE); \ __p4d_free_tlb(tlb, pudp, address); \ } while (0) #endif #define tlb_migrate_finish(mm) do {} while (0) #endif /* _ASM_GENERIC__TLB_H */

Overall Contributors

Aneesh Kumar K.V16123.96%617.65%
Will Deacon14221.13%25.88%
Peter Zijlstra12819.05%514.71%
Linus Torvalds679.97%514.71%
Andrew Morton385.65%38.82%
Matthew Wilcox294.32%12.94%
David Shaohua Li284.17%12.94%
Kirill A. Shutemov202.98%12.94%
Nicholas Piggin142.08%25.88%
Michal Hocko91.34%12.94%
Dave Hansen81.19%12.94%
Alex Shi81.19%12.94%
Jack Steiner71.04%12.94%
Benjamin Herrenschmidt60.89%12.94%
Ingo Molnar30.45%12.94%
David S. Miller30.45%12.94%
Hugh Dickins10.15%12.94%
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