LXR linux/arch/microblaze/include/asm/mmu_context

   1/* SPDX-License-Identifier: GPL-2.0 */
   2/*
   3 * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
   4 * Copyright (C) 2008-2009 PetaLogix
   5 * Copyright (C) 2006 Atmark Techno, Inc.
   6 */
   7
   8#ifndef _ASM_MICROBLAZE_MMU_CONTEXT_H
   9#define _ASM_MICROBLAZE_MMU_CONTEXT_H
  10
  11#include <linux/atomic.h>
  12#include <linux/mm_types.h>
  13#include <linux/sched.h>
  14
  15#include <asm/bitops.h>
  16#include <asm/mmu.h>
  17#include <asm-generic/mm_hooks.h>
  18
  19# ifdef __KERNEL__
  20/*
  21 * This function defines the mapping from contexts to VSIDs (virtual
  22 * segment IDs).  We use a skew on both the context and the high 4 bits
  23 * of the 32-bit virtual address (the "effective segment ID") in order
  24 * to spread out the entries in the MMU hash table.
  25 */
  26# define CTX_TO_VSID(ctx, va)   (((ctx) * (897 * 16) + ((va) >> 28) * 0x111) \
  27                                 & 0xffffff)
  28
  29/*
  30   MicroBlaze has 256 contexts, so we can just rotate through these
  31   as a way of "switching" contexts.  If the TID of the TLB is zero,
  32   the PID/TID comparison is disabled, so we can use a TID of zero
  33   to represent all kernel pages as shared among all contexts.
  34 */
  35
  36# define NO_CONTEXT     256
  37# define LAST_CONTEXT   255
  38# define FIRST_CONTEXT  1
  39
  40/*
  41 * Set the current MMU context.
  42 * This is done byloading up the segment registers for the user part of the
  43 * address space.
  44 *
  45 * Since the PGD is immediately available, it is much faster to simply
  46 * pass this along as a second parameter, which is required for 8xx and
  47 * can be used for debugging on all processors (if you happen to have
  48 * an Abatron).
  49 */
  50extern void set_context(mm_context_t context, pgd_t *pgd);
  51
  52/*
  53 * Bitmap of contexts in use.
  54 * The size of this bitmap is LAST_CONTEXT + 1 bits.
  55 */
  56extern unsigned long context_map[];
  57
  58/*
  59 * This caches the next context number that we expect to be free.
  60 * Its use is an optimization only, we can't rely on this context
  61 * number to be free, but it usually will be.
  62 */
  63extern mm_context_t next_mmu_context;
  64
  65/*
  66 * Since we don't have sufficient contexts to give one to every task
  67 * that could be in the system, we need to be able to steal contexts.
  68 * These variables support that.
  69 */
  70extern atomic_t nr_free_contexts;
  71extern struct mm_struct *context_mm[LAST_CONTEXT+1];
  72extern void steal_context(void);
  73
  74/*
  75 * Get a new mmu context for the address space described by `mm'.
  76 */
  77static inline void get_mmu_context(struct mm_struct *mm)
  78{
  79        mm_context_t ctx;
  80
  81        if (mm->context != NO_CONTEXT)
  82                return;
  83        while (atomic_dec_if_positive(&nr_free_contexts) < 0)
  84                steal_context();
  85        ctx = next_mmu_context;
  86        while (test_and_set_bit(ctx, context_map)) {
  87                ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
  88                if (ctx > LAST_CONTEXT)
  89                        ctx = 0;
  90        }
  91        next_mmu_context = (ctx + 1) & LAST_CONTEXT;
  92        mm->context = ctx;
  93        context_mm[ctx] = mm;
  94}
  95
  96/*
  97 * Set up the context for a new address space.
  98 */
  99# define init_new_context(tsk, mm)      (((mm)->context = NO_CONTEXT), 0)
 100
 101/*
 102 * We're finished using the context for an address space.
 103 */
 104#define destroy_context destroy_context
 105static inline void destroy_context(struct mm_struct *mm)
 106{
 107        if (mm->context != NO_CONTEXT) {
 108                clear_bit(mm->context, context_map);
 109                mm->context = NO_CONTEXT;
 110                atomic_inc(&nr_free_contexts);
 111        }
 112}
 113
 114static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 115                             struct task_struct *tsk)
 116{
 117        tsk->thread.pgdir = next->pgd;
 118        get_mmu_context(next);
 119        set_context(next->context, next->pgd);
 120}
 121
 122/*
 123 * After we have set current->mm to a new value, this activates
 124 * the context for the new mm so we see the new mappings.
 125 */
 126#define activate_mm activate_mm
 127static inline void activate_mm(struct mm_struct *active_mm,
 128                        struct mm_struct *mm)
 129{
 130        current->thread.pgdir = mm->pgd;
 131        get_mmu_context(mm);
 132        set_context(mm->context, mm->pgd);
 133}
 134
 135extern void mmu_context_init(void);
 136
 137#include <asm-generic/mmu_context.h>
 138
 139# endif /* __KERNEL__ */
 140#endif /* _ASM_MICROBLAZE_MMU_CONTEXT_H */
 141