mmu_context_mm.h

  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 */