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mmu_context.h
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1 #ifndef _ASM_IA64_MMU_CONTEXT_H
2 #define _ASM_IA64_MMU_CONTEXT_H
3 
4 /*
5  * Copyright (C) 1998-2002 Hewlett-Packard Co
6  * David Mosberger-Tang <[email protected]>
7  */
8 
9 /*
10  * Routines to manage the allocation of task context numbers. Task context
11  * numbers are used to reduce or eliminate the need to perform TLB flushes
12  * due to context switches. Context numbers are implemented using ia-64
13  * region ids. Since the IA-64 TLB does not consider the region number when
14  * performing a TLB lookup, we need to assign a unique region id to each
15  * region in a process. We use the least significant three bits in aregion
16  * id for this purpose.
17  */
18 
19 #define IA64_REGION_ID_KERNEL 0 /* the kernel's region id (tlb.c depends on this being 0) */
20 
21 #define ia64_rid(ctx,addr) (((ctx) << 3) | (addr >> 61))
22 
23 # include <asm/page.h>
24 # ifndef __ASSEMBLY__
25 
26 #include <linux/compiler.h>
27 #include <linux/percpu.h>
28 #include <linux/sched.h>
29 #include <linux/spinlock.h>
30 
31 #include <asm/processor.h>
32 #include <asm-generic/mm_hooks.h>
33 
34 struct ia64_ctx {
36  unsigned int next; /* next context number to use */
37  unsigned int limit; /* available free range */
38  unsigned int max_ctx; /* max. context value supported by all CPUs */
39  /* call wrap_mmu_context when next >= max */
40  unsigned long *bitmap; /* bitmap size is max_ctx+1 */
41  unsigned long *flushmap;/* pending rid to be flushed */
42 };
43 
44 extern struct ia64_ctx ia64_ctx;
45 DECLARE_PER_CPU(u8, ia64_need_tlb_flush);
46 
47 extern void mmu_context_init (void);
48 extern void wrap_mmu_context (struct mm_struct *mm);
49 
50 static inline void
51 enter_lazy_tlb (struct mm_struct *mm, struct task_struct *tsk)
52 {
53 }
54 
55 /*
56  * When the context counter wraps around all TLBs need to be flushed because
57  * an old context number might have been reused. This is signalled by the
58  * ia64_need_tlb_flush per-CPU variable, which is checked in the routine
59  * below. Called by activate_mm(). <[email protected]>
60  */
61 static inline void
62 delayed_tlb_flush (void)
63 {
64  extern void local_flush_tlb_all (void);
65  unsigned long flags;
66 
67  if (unlikely(__ia64_per_cpu_var(ia64_need_tlb_flush))) {
69  if (__ia64_per_cpu_var(ia64_need_tlb_flush)) {
71  __ia64_per_cpu_var(ia64_need_tlb_flush) = 0;
72  }
73  spin_unlock_irqrestore(&ia64_ctx.lock, flags);
74  }
75 }
76 
77 static inline nv_mm_context_t
78 get_mmu_context (struct mm_struct *mm)
79 {
80  unsigned long flags;
82 
83  if (likely(context))
84  goto out;
85 
87  /* re-check, now that we've got the lock: */
88  context = mm->context;
89  if (context == 0) {
90  cpumask_clear(mm_cpumask(mm));
91  if (ia64_ctx.next >= ia64_ctx.limit) {
97  wrap_mmu_context(mm);
98  }
99  mm->context = context = ia64_ctx.next++;
100  __set_bit(context, ia64_ctx.bitmap);
101  }
102  spin_unlock_irqrestore(&ia64_ctx.lock, flags);
103 out:
104  /*
105  * Ensure we're not starting to use "context" before any old
106  * uses of it are gone from our TLB.
107  */
108  delayed_tlb_flush();
109 
110  return context;
111 }
112 
113 /*
114  * Initialize context number to some sane value. MM is guaranteed to be a
115  * brand-new address-space, so no TLB flushing is needed, ever.
116  */
117 static inline int
118 init_new_context (struct task_struct *p, struct mm_struct *mm)
119 {
120  mm->context = 0;
121  return 0;
122 }
123 
124 static inline void
125 destroy_context (struct mm_struct *mm)
126 {
127  /* Nothing to do. */
128 }
129 
130 static inline void
131 reload_context (nv_mm_context_t context)
132 {
133  unsigned long rid;
134  unsigned long rid_incr = 0;
135  unsigned long rr0, rr1, rr2, rr3, rr4, old_rr4;
136 
137  old_rr4 = ia64_get_rr(RGN_BASE(RGN_HPAGE));
138  rid = context << 3; /* make space for encoding the region number */
139  rid_incr = 1 << 8;
140 
141  /* encode the region id, preferred page size, and VHPT enable bit: */
142  rr0 = (rid << 8) | (PAGE_SHIFT << 2) | 1;
143  rr1 = rr0 + 1*rid_incr;
144  rr2 = rr0 + 2*rid_incr;
145  rr3 = rr0 + 3*rid_incr;
146  rr4 = rr0 + 4*rid_incr;
147 #ifdef CONFIG_HUGETLB_PAGE
148  rr4 = (rr4 & (~(0xfcUL))) | (old_rr4 & 0xfc);
149 
150 # if RGN_HPAGE != 4
151 # error "reload_context assumes RGN_HPAGE is 4"
152 # endif
153 #endif
154 
155  ia64_set_rr0_to_rr4(rr0, rr1, rr2, rr3, rr4);
156  ia64_srlz_i(); /* srlz.i implies srlz.d */
157 }
158 
159 /*
160  * Must be called with preemption off
161  */
162 static inline void
163 activate_context (struct mm_struct *mm)
164 {
166 
167  do {
168  context = get_mmu_context(mm);
169  if (!cpumask_test_cpu(smp_processor_id(), mm_cpumask(mm)))
170  cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
171  reload_context(context);
172  /*
173  * in the unlikely event of a TLB-flush by another thread,
174  * redo the load.
175  */
176  } while (unlikely(context != mm->context));
177 }
178 
179 #define deactivate_mm(tsk,mm) do { } while (0)
180 
181 /*
182  * Switch from address space PREV to address space NEXT.
183  */
184 static inline void
185 activate_mm (struct mm_struct *prev, struct mm_struct *next)
186 {
187  /*
188  * We may get interrupts here, but that's OK because interrupt
189  * handlers cannot touch user-space.
190  */
192  activate_context(next);
193 }
194 
195 #define switch_mm(prev_mm,next_mm,next_task) activate_mm(prev_mm, next_mm)
196 
197 # endif /* ! __ASSEMBLY__ */
198 #endif /* _ASM_IA64_MMU_CONTEXT_H */