include/asm-ia64/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 numbers are
  11  * used to reduce or eliminate the need to perform TLB flushes due to context switches.
  12  * Context numbers are implemented using ia-64 region ids.  Since the IA-64 TLB does not
  13  * consider the region number when performing a TLB lookup, we need to assign a unique
  14  * region id to each region in a process.  We use the least significant three bits in a
  15  * region id for this purpose.
  16  */
  17
  18 #define IA64_REGION_ID_KERNEL   0 /* the kernel's region id (tlb.c depends on this being 0) */
  19
  20 #define ia64_rid(ctx,addr)      (((ctx) << 3) | (addr >> 61))
  21
  22 # ifndef __ASSEMBLY__
  23
  24 #include <linux/compiler.h>
  25 #include <linux/percpu.h>
  26 #include <linux/sched.h>
  27 #include <linux/spinlock.h>
  28
  29 #include <asm/processor.h>
  30
  31 struct ia64_ctx {
  32         spinlock_t lock;
  33         unsigned int next;      /* next context number to use */
  34         unsigned int limit;     /* next >= limit => must call wrap_mmu_context() */
  35         unsigned int max_ctx;   /* max. context value supported by all CPUs */
  36 };
  37
  38 extern struct ia64_ctx ia64_ctx;
  39 DECLARE_PER_CPU(u8, ia64_need_tlb_flush);
  40
  41 extern void wrap_mmu_context (struct mm_struct *mm);
  42
  43 static inline void
  44 enter_lazy_tlb (struct mm_struct *mm, struct task_struct *tsk)
  45 {
  46 }
  47
  48 /*
  49  * When the context counter wraps around all TLBs need to be flushed because an old
  50  * context number might have been reused. This is signalled by the ia64_need_tlb_flush
  51  * per-CPU variable, which is checked in the routine below. Called by activate_mm().
  52  * <efocht@ess.nec.de>
  53  */
  54 static inline void
  55 delayed_tlb_flush (void)
  56 {
  57         extern void local_flush_tlb_all (void);
  58
  59         if (unlikely(__ia64_per_cpu_var(ia64_need_tlb_flush))) {
  60                 local_flush_tlb_all();
  61                 __ia64_per_cpu_var(ia64_need_tlb_flush) = 0;
  62         }
  63 }
  64
  65 static inline mm_context_t
  66 get_mmu_context (struct mm_struct *mm)
  67 {
  68         unsigned long flags;
  69         mm_context_t context = mm->context;
  70
  71         if (context)
  72                 return context;
  73
  74         spin_lock_irqsave(&ia64_ctx.lock, flags);
  75         {
  76                 /* re-check, now that we've got the lock: */
  77                 context = mm->context;
  78                 if (context == 0) {
  79                         cpus_clear(mm->cpu_vm_mask);
  80                         if (ia64_ctx.next >= ia64_ctx.limit)
  81                                 wrap_mmu_context(mm);
  82                         mm->context = context = ia64_ctx.next++;
  83                 }
  84         }
  85         spin_unlock_irqrestore(&ia64_ctx.lock, flags);
  86         return context;
  87 }
  88
  89 /*
  90  * Initialize context number to some sane value.  MM is guaranteed to be a brand-new
  91  * address-space, so no TLB flushing is needed, ever.
  92  */
  93 static inline int
  94 init_new_context (struct task_struct *p, struct mm_struct *mm)
  95 {
  96         mm->context = 0;
  97         return 0;
  98 }
  99
 100 static inline void
 101 destroy_context (struct mm_struct *mm)
 102 {
 103         /* Nothing to do.  */
 104 }
 105
 106 static inline void
 107 reload_context (mm_context_t context)
 108 {
 109         unsigned long rid;
 110         unsigned long rid_incr = 0;
 111         unsigned long rr0, rr1, rr2, rr3, rr4, old_rr4;
 112
 113         old_rr4 = ia64_get_rr(0x8000000000000000UL);
 114         rid = context << 3;     /* make space for encoding the region number */
 115         rid_incr = 1 << 8;
 116
 117         /* encode the region id, preferred page size, and VHPT enable bit: */
 118         rr0 = (rid << 8) | (PAGE_SHIFT << 2) | 1;
 119         rr1 = rr0 + 1*rid_incr;
 120         rr2 = rr0 + 2*rid_incr;
 121         rr3 = rr0 + 3*rid_incr;
 122         rr4 = rr0 + 4*rid_incr;
 123 #ifdef  CONFIG_HUGETLB_PAGE
 124         rr4 = (rr4 & (~(0xfcUL))) | (old_rr4 & 0xfc);
 125 #endif
 126
 127         ia64_set_rr(0x0000000000000000UL, rr0);
 128         ia64_set_rr(0x2000000000000000UL, rr1);
 129         ia64_set_rr(0x4000000000000000UL, rr2);
 130         ia64_set_rr(0x6000000000000000UL, rr3);
 131         ia64_set_rr(0x8000000000000000UL, rr4);
 132         ia64_srlz_i();                  /* srlz.i implies srlz.d */
 133 }
 134
 135 /*
 136  * Must be called with preemption off
 137  */
 138 static inline void
 139 activate_context (struct mm_struct *mm)
 140 {
 141         mm_context_t context;
 142
 143         do {
 144                 context = get_mmu_context(mm);
 145                 if (!cpu_isset(smp_processor_id(), mm->cpu_vm_mask))
 146                         cpu_set(smp_processor_id(), mm->cpu_vm_mask);
 147                 reload_context(context);
 148                 /* in the unlikely event of a TLB-flush by another thread, redo the load: */
 149         } while (unlikely(context != mm->context));
 150 }
 151
 152 #define deactivate_mm(tsk,mm)   do { } while (0)
 153
 154 /*
 155  * Switch from address space PREV to address space NEXT.
 156  */
 157 static inline void
 158 activate_mm (struct mm_struct *prev, struct mm_struct *next)
 159 {
 160         delayed_tlb_flush();
 161
 162         /*
 163          * We may get interrupts here, but that's OK because interrupt handlers cannot
 164          * touch user-space.
 165          */
 166         ia64_set_kr(IA64_KR_PT_BASE, __pa(next->pgd));
 167         activate_context(next);
 168 }
 169
 170 #define switch_mm(prev_mm,next_mm,next_task)    activate_mm(prev_mm, next_mm)
 171
 172 # endif /* ! __ASSEMBLY__ */
 173 #endif /* _ASM_IA64_MMU_CONTEXT_H */