1 /* 2 * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu> 3 * Copyright (C) 2008-2009 PetaLogix 4 * Copyright (C) 2006 Atmark Techno, Inc. 5 * 6 * This file is subject to the terms and conditions of the GNU General Public 7 * License. See the file "COPYING" in the main directory of this archive 8 * for more details. 9 */ 10 11 #ifndef _ASM_MICROBLAZE_MMU_CONTEXT_H 12 #define _ASM_MICROBLAZE_MMU_CONTEXT_H 13 14 #include <linux/atomic.h> 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 static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk) 37 { 38 } 39 40 # define NO_CONTEXT 256 41 # define LAST_CONTEXT 255 42 # define FIRST_CONTEXT 1 43 44 /* 45 * Set the current MMU context. 46 * This is done byloading up the segment registers for the user part of the 47 * address space. 48 * 49 * Since the PGD is immediately available, it is much faster to simply 50 * pass this along as a second parameter, which is required for 8xx and 51 * can be used for debugging on all processors (if you happen to have 52 * an Abatron). 53 */ 54 extern void set_context(mm_context_t context, pgd_t *pgd); 55 56 /* 57 * Bitmap of contexts in use. 58 * The size of this bitmap is LAST_CONTEXT + 1 bits. 59 */ 60 extern unsigned long context_map[]; 61 62 /* 63 * This caches the next context number that we expect to be free. 64 * Its use is an optimization only, we can't rely on this context 65 * number to be free, but it usually will be. 66 */ 67 extern mm_context_t next_mmu_context; 68 69 /* 70 * Since we don't have sufficient contexts to give one to every task 71 * that could be in the system, we need to be able to steal contexts. 72 * These variables support that. 73 */ 74 extern atomic_t nr_free_contexts; 75 extern struct mm_struct *context_mm[LAST_CONTEXT+1]; 76 extern void steal_context(void); 77 78 /* 79 * Get a new mmu context for the address space described by `mm'. 80 */ 81 static inline void get_mmu_context(struct mm_struct *mm) 82 { 83 mm_context_t ctx; 84 85 if (mm->context != NO_CONTEXT) 86 return; 87 while (atomic_dec_if_positive(&nr_free_contexts) < 0) 88 steal_context(); 89 ctx = next_mmu_context; 90 while (test_and_set_bit(ctx, context_map)) { 91 ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx); 92 if (ctx > LAST_CONTEXT) 93 ctx = 0; 94 } 95 next_mmu_context = (ctx + 1) & LAST_CONTEXT; 96 mm->context = ctx; 97 context_mm[ctx] = mm; 98 } 99 100 /* 101 * Set up the context for a new address space. 102 */ 103 # define init_new_context(tsk, mm) (((mm)->context = NO_CONTEXT), 0) 104 105 /* 106 * We're finished using the context for an address space. 107 */ 108 static inline void destroy_context(struct mm_struct *mm) 109 { 110 if (mm->context != NO_CONTEXT) { 111 clear_bit(mm->context, context_map); 112 mm->context = NO_CONTEXT; 113 atomic_inc(&nr_free_contexts); 114 } 115 } 116 117 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, 118 struct task_struct *tsk) 119 { 120 tsk->thread.pgdir = next->pgd; 121 get_mmu_context(next); 122 set_context(next->context, next->pgd); 123 } 124 125 /* 126 * After we have set current->mm to a new value, this activates 127 * the context for the new mm so we see the new mappings. 128 */ 129 static inline void activate_mm(struct mm_struct *active_mm, 130 struct mm_struct *mm) 131 { 132 current->thread.pgdir = mm->pgd; 133 get_mmu_context(mm); 134 set_context(mm->context, mm->pgd); 135 } 136 137 extern void mmu_context_init(void); 138 139 # endif /* __KERNEL__ */ 140 #endif /* _ASM_MICROBLAZE_MMU_CONTEXT_H */ 141