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| 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 | */ |
| 50 | extern 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 | */ |
| 56 | extern 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 | */ |
| 63 | extern 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 | */ |
| 70 | extern atomic_t nr_free_contexts; |
| 71 | extern struct mm_struct *context_mm[LAST_CONTEXT+1]; |
| 72 | extern void steal_context(void); |
| 73 | |
| 74 | /* |
| 75 | * Get a new mmu context for the address space described by `mm'. |
| 76 | */ |
| 77 | static 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 |
| 105 | static 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 | |
| 114 | static 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 |
| 127 | static 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 | |
| 135 | extern 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 |
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