arch/ppc64/mm/stab.c

   1 /*
   2  * PowerPC64 Segment Translation Support.
   3  *
   4  * Dave Engebretsen and Mike Corrigan {engebret|mikejc}@us.ibm.com
   5  *    Copyright (c) 2001 Dave Engebretsen
   6  *
   7  * Copyright (C) 2002 Anton Blanchard <anton@au.ibm.com>, IBM
   8  *
   9  *      This program is free software; you can redistribute it and/or
  10  *      modify it under the terms of the GNU General Public License
  11  *      as published by the Free Software Foundation; either version
  12  *      2 of the License, or (at your option) any later version.
  13  */
  14
  15 #include <linux/config.h>
  16 #include <asm/pgtable.h>
  17 #include <asm/mmu.h>
  18 #include <asm/mmu_context.h>
  19 #include <asm/paca.h>
  20 #include <asm/cputable.h>
  21
  22 struct stab_entry {
  23         unsigned long esid_data;
  24         unsigned long vsid_data;
  25 };
  26
  27 /* Both the segment table and SLB code uses the following cache */
  28 #define NR_STAB_CACHE_ENTRIES 8
  29 DEFINE_PER_CPU(long, stab_cache_ptr);
  30 DEFINE_PER_CPU(long, stab_cache[NR_STAB_CACHE_ENTRIES]);
  31
  32 /*
  33  * Create a segment table entry for the given esid/vsid pair.
  34  */
  35 static int make_ste(unsigned long stab, unsigned long esid, unsigned long vsid)
  36 {
  37         unsigned long esid_data, vsid_data;
  38         unsigned long entry, group, old_esid, castout_entry, i;
  39         unsigned int global_entry;
  40         struct stab_entry *ste, *castout_ste;
  41         unsigned long kernel_segment = (esid << SID_SHIFT) >= KERNELBASE;
  42
  43         vsid_data = vsid << STE_VSID_SHIFT;
  44         esid_data = esid << SID_SHIFT | STE_ESID_KP | STE_ESID_V;
  45         if (! kernel_segment)
  46                 esid_data |= STE_ESID_KS;
  47
  48         /* Search the primary group first. */
  49         global_entry = (esid & 0x1f) << 3;
  50         ste = (struct stab_entry *)(stab | ((esid & 0x1f) << 7));
  51
  52         /* Find an empty entry, if one exists. */
  53         for (group = 0; group < 2; group++) {
  54                 for (entry = 0; entry < 8; entry++, ste++) {
  55                         if (!(ste->esid_data & STE_ESID_V)) {
  56                                 ste->vsid_data = vsid_data;
  57                                 asm volatile("eieio":::"memory");
  58                                 ste->esid_data = esid_data;
  59                                 return (global_entry | entry);
  60                         }
  61                 }
  62                 /* Now search the secondary group. */
  63                 global_entry = ((~esid) & 0x1f) << 3;
  64                 ste = (struct stab_entry *)(stab | (((~esid) & 0x1f) << 7));
  65         }
  66
  67         /*
  68          * Could not find empty entry, pick one with a round robin selection.
  69          * Search all entries in the two groups.
  70          */
  71         castout_entry = get_paca()->stab_rr;
  72         for (i = 0; i < 16; i++) {
  73                 if (castout_entry < 8) {
  74                         global_entry = (esid & 0x1f) << 3;
  75                         ste = (struct stab_entry *)(stab | ((esid & 0x1f) << 7));
  76                         castout_ste = ste + castout_entry;
  77                 } else {
  78                         global_entry = ((~esid) & 0x1f) << 3;
  79                         ste = (struct stab_entry *)(stab | (((~esid) & 0x1f) << 7));
  80                         castout_ste = ste + (castout_entry - 8);
  81                 }
  82
  83                 /* Dont cast out the first kernel segment */
  84                 if ((castout_ste->esid_data & ESID_MASK) != KERNELBASE)
  85                         break;
  86
  87                 castout_entry = (castout_entry + 1) & 0xf;
  88         }
  89
  90         get_paca()->stab_rr = (castout_entry + 1) & 0xf;
  91
  92         /* Modify the old entry to the new value. */
  93
  94         /* Force previous translations to complete. DRENG */
  95         asm volatile("isync" : : : "memory");
  96
  97         old_esid = castout_ste->esid_data >> SID_SHIFT;
  98         castout_ste->esid_data = 0;             /* Invalidate old entry */
  99
 100         asm volatile("sync" : : : "memory");    /* Order update */
 101
 102         castout_ste->vsid_data = vsid_data;
 103         asm volatile("eieio" : : : "memory");   /* Order update */
 104         castout_ste->esid_data = esid_data;
 105
 106         asm volatile("slbie  %0" : : "r" (old_esid << SID_SHIFT));
 107         /* Ensure completion of slbie */
 108         asm volatile("sync" : : : "memory");
 109
 110         return (global_entry | (castout_entry & 0x7));
 111 }
 112
 113 /*
 114  * Allocate a segment table entry for the given ea and mm
 115  */
 116 static int __ste_allocate(unsigned long ea, struct mm_struct *mm)
 117 {
 118         unsigned long vsid;
 119         unsigned char stab_entry;
 120         unsigned long offset;
 121
 122         /* Kernel or user address? */
 123         if (ea >= KERNELBASE) {
 124                 vsid = get_kernel_vsid(ea);
 125         } else {
 126                 if ((ea >= TASK_SIZE_USER64) || (! mm))
 127                         return 1;
 128
 129                 vsid = get_vsid(mm->context.id, ea);
 130         }
 131
 132         stab_entry = make_ste(get_paca()->stab_addr, GET_ESID(ea), vsid);
 133
 134         if (ea < KERNELBASE) {
 135                 offset = __get_cpu_var(stab_cache_ptr);
 136                 if (offset < NR_STAB_CACHE_ENTRIES)
 137                         __get_cpu_var(stab_cache[offset++]) = stab_entry;
 138                 else
 139                         offset = NR_STAB_CACHE_ENTRIES+1;
 140                 __get_cpu_var(stab_cache_ptr) = offset;
 141
 142                 /* Order update */
 143                 asm volatile("sync":::"memory");
 144         }
 145
 146         return 0;
 147 }
 148
 149 int ste_allocate(unsigned long ea)
 150 {
 151         return __ste_allocate(ea, current->mm);
 152 }
 153
 154 /*
 155  * Do the segment table work for a context switch: flush all user
 156  * entries from the table, then preload some probably useful entries
 157  * for the new task
 158  */
 159 void switch_stab(struct task_struct *tsk, struct mm_struct *mm)
 160 {
 161         struct stab_entry *stab = (struct stab_entry *) get_paca()->stab_addr;
 162         struct stab_entry *ste;
 163         unsigned long offset = __get_cpu_var(stab_cache_ptr);
 164         unsigned long pc = KSTK_EIP(tsk);
 165         unsigned long stack = KSTK_ESP(tsk);
 166         unsigned long unmapped_base;
 167
 168         /* Force previous translations to complete. DRENG */
 169         asm volatile("isync" : : : "memory");
 170
 171         if (offset <= NR_STAB_CACHE_ENTRIES) {
 172                 int i;
 173
 174                 for (i = 0; i < offset; i++) {
 175                         ste = stab + __get_cpu_var(stab_cache[i]);
 176                         ste->esid_data = 0; /* invalidate entry */
 177                 }
 178         } else {
 179                 unsigned long entry;
 180
 181                 /* Invalidate all entries. */
 182                 ste = stab;
 183
 184                 /* Never flush the first entry. */
 185                 ste += 1;
 186                 for (entry = 1;
 187                      entry < (PAGE_SIZE / sizeof(struct stab_entry));
 188                      entry++, ste++) {
 189                         unsigned long ea;
 190                         ea = ste->esid_data & ESID_MASK;
 191                         if (ea < KERNELBASE) {
 192                                 ste->esid_data = 0;
 193                         }
 194                 }
 195         }
 196
 197         asm volatile("sync; slbia; sync":::"memory");
 198
 199         __get_cpu_var(stab_cache_ptr) = 0;
 200
 201         /* Now preload some entries for the new task */
 202         if (test_tsk_thread_flag(tsk, TIF_32BIT))
 203                 unmapped_base = TASK_UNMAPPED_BASE_USER32;
 204         else
 205                 unmapped_base = TASK_UNMAPPED_BASE_USER64;
 206
 207         __ste_allocate(pc, mm);
 208
 209         if (GET_ESID(pc) == GET_ESID(stack))
 210                 return;
 211
 212         __ste_allocate(stack, mm);
 213
 214         if ((GET_ESID(pc) == GET_ESID(unmapped_base))
 215             || (GET_ESID(stack) == GET_ESID(unmapped_base)))
 216                 return;
 217
 218         __ste_allocate(unmapped_base, mm);
 219
 220         /* Order update */
 221         asm volatile("sync" : : : "memory");
 222 }
 223
 224 extern void slb_initialize(void);
 225
 226 /*
 227  * Build an entry for the base kernel segment and put it into
 228  * the segment table or SLB.  All other segment table or SLB
 229  * entries are faulted in.
 230  */
 231 void stab_initialize(unsigned long stab)
 232 {
 233         unsigned long vsid = get_kernel_vsid(KERNELBASE);
 234
 235         if (cpu_has_feature(CPU_FTR_SLB)) {
 236                 slb_initialize();
 237         } else {
 238                 asm volatile("isync; slbia; isync":::"memory");
 239                 make_ste(stab, GET_ESID(KERNELBASE), vsid);
 240
 241                 /* Order update */
 242                 asm volatile("sync":::"memory");
 243         }
 244 }