arch/ia64/include/asm/mmu_context.h

   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 <davidm@hpl.hp.com>
   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 {
  35         spinlock_t lock;
  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(). <efocht@ess.nec.de>
  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))) {
  68                 spin_lock_irqsave(&ia64_ctx.lock, flags);
  69                 if (__ia64_per_cpu_var(ia64_need_tlb_flush)) {
  70                         local_flush_tlb_all();
  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;
  81         nv_mm_context_t context = mm->context;
  82
  83         if (likely(context))
  84                 goto out;
  85
  86         spin_lock_irqsave(&ia64_ctx.lock, flags);
  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) {
  92                         ia64_ctx.next = find_next_zero_bit(ia64_ctx.bitmap,
  93                                         ia64_ctx.max_ctx, ia64_ctx.next);
  94                         ia64_ctx.limit = find_next_bit(ia64_ctx.bitmap,
  95                                         ia64_ctx.max_ctx, ia64_ctx.next);
  96                         if (ia64_ctx.next >= ia64_ctx.max_ctx)
  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 {
 165         nv_mm_context_t context;
 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          */
 191         ia64_set_kr(IA64_KR_PT_BASE, __pa(next->pgd));
 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 */