arch/powerpc/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/memblock.h>
  16
  17 #include <asm/pgtable.h>
  18 #include <asm/mmu.h>
  19 #include <asm/mmu_context.h>
  20 #include <asm/paca.h>
  21 #include <asm/cputable.h>
  22 #include <asm/prom.h>
  23
  24 struct stab_entry {
  25         unsigned long esid_data;
  26         unsigned long vsid_data;
  27 };
  28
  29 #define NR_STAB_CACHE_ENTRIES 8
  30 static DEFINE_PER_CPU(long, stab_cache_ptr);
  31 static DEFINE_PER_CPU(long [NR_STAB_CACHE_ENTRIES], stab_cache);
  32
  33 /*
  34  * Create a segment table entry for the given esid/vsid pair.
  35  */
  36 static int make_ste(unsigned long stab, unsigned long esid, unsigned long vsid)
  37 {
  38         unsigned long esid_data, vsid_data;
  39         unsigned long entry, group, old_esid, castout_entry, i;
  40         unsigned int global_entry;
  41         struct stab_entry *ste, *castout_ste;
  42         unsigned long kernel_segment = (esid << SID_SHIFT) >= PAGE_OFFSET;
  43
  44         vsid_data = vsid << STE_VSID_SHIFT;
  45         esid_data = esid << SID_SHIFT | STE_ESID_KP | STE_ESID_V;
  46         if (! kernel_segment)
  47                 esid_data |= STE_ESID_KS;
  48
  49         /* Search the primary group first. */
  50         global_entry = (esid & 0x1f) << 3;
  51         ste = (struct stab_entry *)(stab | ((esid & 0x1f) << 7));
  52
  53         /* Find an empty entry, if one exists. */
  54         for (group = 0; group < 2; group++) {
  55                 for (entry = 0; entry < 8; entry++, ste++) {
  56                         if (!(ste->esid_data & STE_ESID_V)) {
  57                                 ste->vsid_data = vsid_data;
  58                                 eieio();
  59                                 ste->esid_data = esid_data;
  60                                 return (global_entry | entry);
  61                         }
  62                 }
  63                 /* Now search the secondary group. */
  64                 global_entry = ((~esid) & 0x1f) << 3;
  65                 ste = (struct stab_entry *)(stab | (((~esid) & 0x1f) << 7));
  66         }
  67
  68         /*
  69          * Could not find empty entry, pick one with a round robin selection.
  70          * Search all entries in the two groups.
  71          */
  72         castout_entry = get_paca()->stab_rr;
  73         for (i = 0; i < 16; i++) {
  74                 if (castout_entry < 8) {
  75                         global_entry = (esid & 0x1f) << 3;
  76                         ste = (struct stab_entry *)(stab | ((esid & 0x1f) << 7));
  77                         castout_ste = ste + castout_entry;
  78                 } else {
  79                         global_entry = ((~esid) & 0x1f) << 3;
  80                         ste = (struct stab_entry *)(stab | (((~esid) & 0x1f) << 7));
  81                         castout_ste = ste + (castout_entry - 8);
  82                 }
  83
  84                 /* Dont cast out the first kernel segment */
  85                 if ((castout_ste->esid_data & ESID_MASK) != PAGE_OFFSET)
  86                         break;
  87
  88                 castout_entry = (castout_entry + 1) & 0xf;
  89         }
  90
  91         get_paca()->stab_rr = (castout_entry + 1) & 0xf;
  92
  93         /* Modify the old entry to the new value. */
  94
  95         /* Force previous translations to complete. DRENG */
  96         asm volatile("isync" : : : "memory");
  97
  98         old_esid = castout_ste->esid_data >> SID_SHIFT;
  99         castout_ste->esid_data = 0;             /* Invalidate old entry */
 100
 101         asm volatile("sync" : : : "memory");    /* Order update */
 102
 103         castout_ste->vsid_data = vsid_data;
 104         eieio();                                /* Order update */
 105         castout_ste->esid_data = esid_data;
 106
 107         asm volatile("slbie  %0" : : "r" (old_esid << SID_SHIFT));
 108         /* Ensure completion of slbie */
 109         asm volatile("sync" : : : "memory");
 110
 111         return (global_entry | (castout_entry & 0x7));
 112 }
 113
 114 /*
 115  * Allocate a segment table entry for the given ea and mm
 116  */
 117 static int __ste_allocate(unsigned long ea, struct mm_struct *mm)
 118 {
 119         unsigned long vsid;
 120         unsigned char stab_entry;
 121         unsigned long offset;
 122
 123         /* Kernel or user address? */
 124         if (is_kernel_addr(ea)) {
 125                 vsid = get_kernel_vsid(ea, MMU_SEGSIZE_256M);
 126         } else {
 127                 if ((ea >= TASK_SIZE_USER64) || (! mm))
 128                         return 1;
 129
 130                 vsid = get_vsid(mm->context.id, ea, MMU_SEGSIZE_256M);
 131         }
 132
 133         stab_entry = make_ste(get_paca()->stab_addr, GET_ESID(ea), vsid);
 134
 135         if (!is_kernel_addr(ea)) {
 136                 offset = __get_cpu_var(stab_cache_ptr);
 137                 if (offset < NR_STAB_CACHE_ENTRIES)
 138                         __get_cpu_var(stab_cache[offset++]) = stab_entry;
 139                 else
 140                         offset = NR_STAB_CACHE_ENTRIES+1;
 141                 __get_cpu_var(stab_cache_ptr) = offset;
 142
 143                 /* Order update */
 144                 asm volatile("sync":::"memory");
 145         }
 146
 147         return 0;
 148 }
 149
 150 int ste_allocate(unsigned long ea)
 151 {
 152         return __ste_allocate(ea, current->mm);
 153 }
 154
 155 /*
 156  * Do the segment table work for a context switch: flush all user
 157  * entries from the table, then preload some probably useful entries
 158  * for the new task
 159  */
 160 void switch_stab(struct task_struct *tsk, struct mm_struct *mm)
 161 {
 162         struct stab_entry *stab = (struct stab_entry *) get_paca()->stab_addr;
 163         struct stab_entry *ste;
 164         unsigned long offset;
 165         unsigned long pc = KSTK_EIP(tsk);
 166         unsigned long stack = KSTK_ESP(tsk);
 167         unsigned long unmapped_base;
 168
 169         /* Force previous translations to complete. DRENG */
 170         asm volatile("isync" : : : "memory");
 171
 172         /*
 173          * We need interrupts hard-disabled here, not just soft-disabled,
 174          * so that a PMU interrupt can't occur, which might try to access
 175          * user memory (to get a stack trace) and possible cause an STAB miss
 176          * which would update the stab_cache/stab_cache_ptr per-cpu variables.
 177          */
 178         hard_irq_disable();
 179
 180         offset = __get_cpu_var(stab_cache_ptr);
 181         if (offset <= NR_STAB_CACHE_ENTRIES) {
 182                 int i;
 183
 184                 for (i = 0; i < offset; i++) {
 185                         ste = stab + __get_cpu_var(stab_cache[i]);
 186                         ste->esid_data = 0; /* invalidate entry */
 187                 }
 188         } else {
 189                 unsigned long entry;
 190
 191                 /* Invalidate all entries. */
 192                 ste = stab;
 193
 194                 /* Never flush the first entry. */
 195                 ste += 1;
 196                 for (entry = 1;
 197                      entry < (HW_PAGE_SIZE / sizeof(struct stab_entry));
 198                      entry++, ste++) {
 199                         unsigned long ea;
 200                         ea = ste->esid_data & ESID_MASK;
 201                         if (!is_kernel_addr(ea)) {
 202                                 ste->esid_data = 0;
 203                         }
 204                 }
 205         }
 206
 207         asm volatile("sync; slbia; sync":::"memory");
 208
 209         __get_cpu_var(stab_cache_ptr) = 0;
 210
 211         /* Now preload some entries for the new task */
 212         if (test_tsk_thread_flag(tsk, TIF_32BIT))
 213                 unmapped_base = TASK_UNMAPPED_BASE_USER32;
 214         else
 215                 unmapped_base = TASK_UNMAPPED_BASE_USER64;
 216
 217         __ste_allocate(pc, mm);
 218
 219         if (GET_ESID(pc) == GET_ESID(stack))
 220                 return;
 221
 222         __ste_allocate(stack, mm);
 223
 224         if ((GET_ESID(pc) == GET_ESID(unmapped_base))
 225             || (GET_ESID(stack) == GET_ESID(unmapped_base)))
 226                 return;
 227
 228         __ste_allocate(unmapped_base, mm);
 229
 230         /* Order update */
 231         asm volatile("sync" : : : "memory");
 232 }
 233
 234 /*
 235  * Allocate segment tables for secondary CPUs.  These must all go in
 236  * the first (bolted) segment, so that do_stab_bolted won't get a
 237  * recursive segment miss on the segment table itself.
 238  */
 239 void __init stabs_alloc(void)
 240 {
 241         int cpu;
 242
 243         if (mmu_has_feature(MMU_FTR_SLB))
 244                 return;
 245
 246         for_each_possible_cpu(cpu) {
 247                 unsigned long newstab;
 248
 249                 if (cpu == 0)
 250                         continue; /* stab for CPU 0 is statically allocated */
 251
 252                 newstab = memblock_alloc_base(HW_PAGE_SIZE, HW_PAGE_SIZE,
 253                                          1<<SID_SHIFT);
 254                 newstab = (unsigned long)__va(newstab);
 255
 256                 memset((void *)newstab, 0, HW_PAGE_SIZE);
 257
 258                 paca[cpu].stab_addr = newstab;
 259                 paca[cpu].stab_real = __pa(newstab);
 260                 printk(KERN_INFO "Segment table for CPU %d at 0x%llx "
 261                        "virtual, 0x%llx absolute\n",
 262                        cpu, paca[cpu].stab_addr, paca[cpu].stab_real);
 263         }
 264 }
 265
 266 /*
 267  * Build an entry for the base kernel segment and put it into
 268  * the segment table or SLB.  All other segment table or SLB
 269  * entries are faulted in.
 270  */
 271 void stab_initialize(unsigned long stab)
 272 {
 273         unsigned long vsid = get_kernel_vsid(PAGE_OFFSET, MMU_SEGSIZE_256M);
 274         unsigned long stabreal;
 275
 276         asm volatile("isync; slbia; isync":::"memory");
 277         make_ste(stab, GET_ESID(PAGE_OFFSET), vsid);
 278
 279         /* Order update */
 280         asm volatile("sync":::"memory");
 281
 282         /* Set ASR */
 283         stabreal = get_paca()->stab_real | 0x1ul;
 284
 285         mtspr(SPRN_ASR, stabreal);
 286 }