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Linux/arch/microblaze/include/asm/mmu_context_mm.h

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  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 

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