arch/microblaze/include/asm/mmu_context_mm.h

   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 */