12874c5fdSThomas Gleixner // SPDX-License-Identifier: GPL-2.0-or-later
217312f25SChristophe Leroy /*
317312f25SChristophe Leroy * This file contains the routines for handling the MMU on those
417312f25SChristophe Leroy * PowerPC implementations where the MMU substantially follows the
517312f25SChristophe Leroy * architecture specification. This includes the 6xx, 7xx, 7xxx,
617312f25SChristophe Leroy * and 8260 implementations but excludes the 8xx and 4xx.
717312f25SChristophe Leroy * -- paulus
817312f25SChristophe Leroy *
917312f25SChristophe Leroy * Derived from arch/ppc/mm/init.c:
1017312f25SChristophe Leroy * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
1117312f25SChristophe Leroy *
1217312f25SChristophe Leroy * Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
1317312f25SChristophe Leroy * and Cort Dougan (PReP) (cort@cs.nmt.edu)
1417312f25SChristophe Leroy * Copyright (C) 1996 Paul Mackerras
1517312f25SChristophe Leroy *
1617312f25SChristophe Leroy * Derived from "arch/i386/mm/init.c"
1717312f25SChristophe Leroy * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
1817312f25SChristophe Leroy */
1917312f25SChristophe Leroy
2017312f25SChristophe Leroy #include <linux/mm.h>
2117312f25SChristophe Leroy #include <linux/init.h>
2217312f25SChristophe Leroy #include <linux/export.h>
2317312f25SChristophe Leroy
2417312f25SChristophe Leroy #include <asm/mmu_context.h>
2517312f25SChristophe Leroy
2617312f25SChristophe Leroy /*
27863771a2SChristophe Leroy * Room for two PTE pointers, usually the kernel and current user pointers
28863771a2SChristophe Leroy * to their respective root page table.
29863771a2SChristophe Leroy */
30863771a2SChristophe Leroy void *abatron_pteptrs[2];
31863771a2SChristophe Leroy
32863771a2SChristophe Leroy /*
3317312f25SChristophe Leroy * On 32-bit PowerPC 6xx/7xx/7xxx CPUs, we use a set of 16 VSIDs
3417312f25SChristophe Leroy * (virtual segment identifiers) for each context. Although the
3517312f25SChristophe Leroy * hardware supports 24-bit VSIDs, and thus >1 million contexts,
3617312f25SChristophe Leroy * we only use 32,768 of them. That is ample, since there can be
3717312f25SChristophe Leroy * at most around 30,000 tasks in the system anyway, and it means
3817312f25SChristophe Leroy * that we can use a bitmap to indicate which contexts are in use.
3917312f25SChristophe Leroy * Using a bitmap means that we entirely avoid all of the problems
4017312f25SChristophe Leroy * that we used to have when the context number overflowed,
4117312f25SChristophe Leroy * particularly on SMP systems.
4217312f25SChristophe Leroy * -- paulus.
4317312f25SChristophe Leroy */
4417312f25SChristophe Leroy #define NO_CONTEXT ((unsigned long) -1)
4517312f25SChristophe Leroy #define LAST_CONTEXT 32767
4617312f25SChristophe Leroy #define FIRST_CONTEXT 1
4717312f25SChristophe Leroy
4817312f25SChristophe Leroy static unsigned long next_mmu_context;
4917312f25SChristophe Leroy static unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
5017312f25SChristophe Leroy
__init_new_context(void)5117312f25SChristophe Leroy unsigned long __init_new_context(void)
5217312f25SChristophe Leroy {
5317312f25SChristophe Leroy unsigned long ctx = next_mmu_context;
5417312f25SChristophe Leroy
5517312f25SChristophe Leroy while (test_and_set_bit(ctx, context_map)) {
5617312f25SChristophe Leroy ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
5717312f25SChristophe Leroy if (ctx > LAST_CONTEXT)
5817312f25SChristophe Leroy ctx = 0;
5917312f25SChristophe Leroy }
6017312f25SChristophe Leroy next_mmu_context = (ctx + 1) & LAST_CONTEXT;
6117312f25SChristophe Leroy
6217312f25SChristophe Leroy return ctx;
6317312f25SChristophe Leroy }
6417312f25SChristophe Leroy EXPORT_SYMBOL_GPL(__init_new_context);
6517312f25SChristophe Leroy
6617312f25SChristophe Leroy /*
6717312f25SChristophe Leroy * Set up the context for a new address space.
6817312f25SChristophe Leroy */
init_new_context(struct task_struct * t,struct mm_struct * mm)6917312f25SChristophe Leroy int init_new_context(struct task_struct *t, struct mm_struct *mm)
7017312f25SChristophe Leroy {
7117312f25SChristophe Leroy mm->context.id = __init_new_context();
7270428da9SChristophe Leroy mm->context.sr0 = CTX_TO_VSID(mm->context.id, 0);
7370428da9SChristophe Leroy
74*38bb171bSChristophe Leroy if (IS_ENABLED(CONFIG_PPC_KUEP))
7570428da9SChristophe Leroy mm->context.sr0 |= SR_NX;
7670428da9SChristophe Leroy if (!kuap_is_disabled())
7770428da9SChristophe Leroy mm->context.sr0 |= SR_KS;
7817312f25SChristophe Leroy
7917312f25SChristophe Leroy return 0;
8017312f25SChristophe Leroy }
8117312f25SChristophe Leroy
8217312f25SChristophe Leroy /*
8317312f25SChristophe Leroy * Free a context ID. Make sure to call this with preempt disabled!
8417312f25SChristophe Leroy */
__destroy_context(unsigned long ctx)8517312f25SChristophe Leroy void __destroy_context(unsigned long ctx)
8617312f25SChristophe Leroy {
8717312f25SChristophe Leroy clear_bit(ctx, context_map);
8817312f25SChristophe Leroy }
8917312f25SChristophe Leroy EXPORT_SYMBOL_GPL(__destroy_context);
9017312f25SChristophe Leroy
9117312f25SChristophe Leroy /*
9217312f25SChristophe Leroy * We're finished using the context for an address space.
9317312f25SChristophe Leroy */
destroy_context(struct mm_struct * mm)9417312f25SChristophe Leroy void destroy_context(struct mm_struct *mm)
9517312f25SChristophe Leroy {
9617312f25SChristophe Leroy preempt_disable();
9717312f25SChristophe Leroy if (mm->context.id != NO_CONTEXT) {
9817312f25SChristophe Leroy __destroy_context(mm->context.id);
9917312f25SChristophe Leroy mm->context.id = NO_CONTEXT;
10017312f25SChristophe Leroy }
10117312f25SChristophe Leroy preempt_enable();
10217312f25SChristophe Leroy }
10317312f25SChristophe Leroy
10417312f25SChristophe Leroy /*
10517312f25SChristophe Leroy * Initialize the context management stuff.
10617312f25SChristophe Leroy */
mmu_context_init(void)10717312f25SChristophe Leroy void __init mmu_context_init(void)
10817312f25SChristophe Leroy {
10917312f25SChristophe Leroy /* Reserve context 0 for kernel use */
11017312f25SChristophe Leroy context_map[0] = (1 << FIRST_CONTEXT) - 1;
11117312f25SChristophe Leroy next_mmu_context = FIRST_CONTEXT;
11217312f25SChristophe Leroy }
113863771a2SChristophe Leroy
switch_mmu_context(struct mm_struct * prev,struct mm_struct * next,struct task_struct * tsk)114863771a2SChristophe Leroy void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next, struct task_struct *tsk)
115863771a2SChristophe Leroy {
116863771a2SChristophe Leroy long id = next->context.id;
117863771a2SChristophe Leroy
118863771a2SChristophe Leroy if (id < 0)
119863771a2SChristophe Leroy panic("mm_struct %p has no context ID", next);
120863771a2SChristophe Leroy
121863771a2SChristophe Leroy isync();
122863771a2SChristophe Leroy
12370428da9SChristophe Leroy update_user_segments(next->context.sr0);
124863771a2SChristophe Leroy
125863771a2SChristophe Leroy if (IS_ENABLED(CONFIG_BDI_SWITCH))
126863771a2SChristophe Leroy abatron_pteptrs[1] = next->pgd;
127863771a2SChristophe Leroy
128863771a2SChristophe Leroy if (!mmu_has_feature(MMU_FTR_HPTE_TABLE))
129863771a2SChristophe Leroy mtspr(SPRN_SDR1, rol32(__pa(next->pgd), 4) & 0xffff01ff);
130863771a2SChristophe Leroy
131863771a2SChristophe Leroy mb(); /* sync */
132863771a2SChristophe Leroy isync();
133863771a2SChristophe Leroy }
134863771a2SChristophe Leroy EXPORT_SYMBOL(switch_mmu_context);
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