1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * This file contains the routines for handling the MMU.
4 *
5 *    Copyright (C) 2007 Xilinx, Inc.  All rights reserved.
6 *
7 *  Derived from arch/ppc/mm/4xx_mmu.c:
8 *  -- paulus
9 *
10 *  Derived from arch/ppc/mm/init.c:
11 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
12 *
13 *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
14 *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
15 *    Copyright (C) 1996 Paul Mackerras
16 *  Amiga/APUS changes by Jesper Skov (jskov@cygnus.co.uk).
17 *
18 *  Derived from "arch/i386/mm/init.c"
19 *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
20 */
21
22#include <linux/mm.h>
23#include <linux/init.h>
24
25#include <asm/tlbflush.h>
26#include <asm/mmu_context.h>
27
28mm_context_t next_mmu_context;
29unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
30atomic_t nr_free_contexts;
31struct mm_struct *context_mm[LAST_CONTEXT+1];
32
33/*
34 * Initialize the context management stuff.
35 */
36void __init mmu_context_init(void)
37{
38	/*
39	 * The use of context zero is reserved for the kernel.
40	 * This code assumes FIRST_CONTEXT < 32.
41	 */
42	context_map[0] = (1 << FIRST_CONTEXT) - 1;
43	next_mmu_context = FIRST_CONTEXT;
44	atomic_set(&nr_free_contexts, LAST_CONTEXT - FIRST_CONTEXT + 1);
45}
46
47/*
48 * Steal a context from a task that has one at the moment.
49 *
50 * This isn't an LRU system, it just frees up each context in
51 * turn (sort-of pseudo-random replacement :).  This would be the
52 * place to implement an LRU scheme if anyone were motivated to do it.
53 */
54void steal_context(void)
55{
56	struct mm_struct *mm;
57
58	/* free up context `next_mmu_context' */
59	/* if we shouldn't free context 0, don't... */
60	if (next_mmu_context < FIRST_CONTEXT)
61		next_mmu_context = FIRST_CONTEXT;
62	mm = context_mm[next_mmu_context];
63	flush_tlb_mm(mm);
64	destroy_context(mm);
65}
66