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 #include <asm/abs_addr.h>
  24
  25 struct stab_entry {
  26         unsigned long esid_data;
  27         unsigned long vsid_data;
  28 };
  29
  30 #define NR_STAB_CACHE_ENTRIES 8
  31 static DEFINE_PER_CPU(long, stab_cache_ptr);
  32 static DEFINE_PER_CPU(long [NR_STAB_CACHE_ENTRIES], stab_cache);
  33
  34 /*
  35  * Create a segment table entry for the given esid/vsid pair.
  36  */
  37 static int make_ste(unsigned long stab, unsigned long esid, unsigned long vsid)
  38 {
  39         unsigned long esid_data, vsid_data;
  40         unsigned long entry, group, old_esid, castout_entry, i;
  41         unsigned int global_entry;
  42         struct stab_entry *ste, *castout_ste;
  43         unsigned long kernel_segment = (esid << SID_SHIFT) >= PAGE_OFFSET;
  44
  45         vsid_data = vsid << STE_VSID_SHIFT;
  46         esid_data = esid << SID_SHIFT | STE_ESID_KP | STE_ESID_V;
  47         if (! kernel_segment)
  48                 esid_data |= STE_ESID_KS;
  49
  50         /* Search the primary group first. */
  51         global_entry = (esid & 0x1f) << 3;
  52         ste = (struct stab_entry *)(stab | ((esid & 0x1f) << 7));
  53
  54         /* Find an empty entry, if one exists. */
  55         for (group = 0; group < 2; group++) {
  56                 for (entry = 0; entry < 8; entry++, ste++) {
  57                         if (!(ste->esid_data & STE_ESID_V)) {
  58                                 ste->vsid_data = vsid_data;
  59                                 eieio();
  60                                 ste->esid_data = esid_data;
  61                                 return (global_entry | entry);
  62                         }
  63                 }
  64                 /* Now search the secondary group. */
  65                 global_entry = ((~esid) & 0x1f) << 3;
  66                 ste = (struct stab_entry *)(stab | (((~esid) & 0x1f) << 7));
  67         }
  68
  69         /*
  70          * Could not find empty entry, pick one with a round robin selection.
  71          * Search all entries in the two groups.
  72          */
  73         castout_entry = get_paca()->stab_rr;
  74         for (i = 0; i < 16; i++) {
  75                 if (castout_entry < 8) {
  76                         global_entry = (esid & 0x1f) << 3;
  77                         ste = (struct stab_entry *)(stab | ((esid & 0x1f) << 7));
  78                         castout_ste = ste + castout_entry;
  79                 } else {
  80                         global_entry = ((~esid) & 0x1f) << 3;
  81                         ste = (struct stab_entry *)(stab | (((~esid) & 0x1f) << 7));
  82                         castout_ste = ste + (castout_entry - 8);
  83                 }
  84
  85                 /* Dont cast out the first kernel segment */
  86                 if ((castout_ste->esid_data & ESID_MASK) != PAGE_OFFSET)
  87                         break;
  88
  89                 castout_entry = (castout_entry + 1) & 0xf;
  90         }
  91
  92         get_paca()->stab_rr = (castout_entry + 1) & 0xf;
  93
  94         /* Modify the old entry to the new value. */
  95
  96         /* Force previous translations to complete. DRENG */
  97         asm volatile("isync" : : : "memory");
  98
  99         old_esid = castout_ste->esid_data >> SID_SHIFT;
 100         castout_ste->esid_data = 0;             /* Invalidate old entry */
 101
 102         asm volatile("sync" : : : "memory");    /* Order update */
 103
 104         castout_ste->vsid_data = vsid_data;
 105         eieio();                                /* Order update */
 106         castout_ste->esid_data = esid_data;
 107
 108         asm volatile("slbie  %0" : : "r" (old_esid << SID_SHIFT));
 109         /* Ensure completion of slbie */
 110         asm volatile("sync" : : : "memory");
 111
 112         return (global_entry | (castout_entry & 0x7));
 113 }
 114
 115 /*
 116  * Allocate a segment table entry for the given ea and mm
 117  */
 118 static int __ste_allocate(unsigned long ea, struct mm_struct *mm)
 119 {
 120         unsigned long vsid;
 121         unsigned char stab_entry;
 122         unsigned long offset;
 123
 124         /* Kernel or user address? */
 125         if (is_kernel_addr(ea)) {
 126                 vsid = get_kernel_vsid(ea, MMU_SEGSIZE_256M);
 127         } else {
 128                 if ((ea >= TASK_SIZE_USER64) || (! mm))
 129                         return 1;
 130
 131                 vsid = get_vsid(mm->context.id, ea, MMU_SEGSIZE_256M);
 132         }
 133
 134         stab_entry = make_ste(get_paca()->stab_addr, GET_ESID(ea), vsid);
 135
 136         if (!is_kernel_addr(ea)) {
 137                 offset = __get_cpu_var(stab_cache_ptr);
 138                 if (offset < NR_STAB_CACHE_ENTRIES)
 139                         __get_cpu_var(stab_cache[offset++]) = stab_entry;
 140                 else
 141                         offset = NR_STAB_CACHE_ENTRIES+1;
 142                 __get_cpu_var(stab_cache_ptr) = offset;
 143
 144                 /* Order update */
 145                 asm volatile("sync":::"memory");
 146         }
 147
 148         return 0;
 149 }
 150
 151 int ste_allocate(unsigned long ea)
 152 {
 153         return __ste_allocate(ea, current->mm);
 154 }
 155
 156 /*
 157  * Do the segment table work for a context switch: flush all user
 158  * entries from the table, then preload some probably useful entries
 159  * for the new task
 160  */
 161 void switch_stab(struct task_struct *tsk, struct mm_struct *mm)
 162 {
 163         struct stab_entry *stab = (struct stab_entry *) get_paca()->stab_addr;
 164         struct stab_entry *ste;
 165         unsigned long offset;
 166         unsigned long pc = KSTK_EIP(tsk);
 167         unsigned long stack = KSTK_ESP(tsk);
 168         unsigned long unmapped_base;
 169
 170         /* Force previous translations to complete. DRENG */
 171         asm volatile("isync" : : : "memory");
 172
 173         /*
 174          * We need interrupts hard-disabled here, not just soft-disabled,
 175          * so that a PMU interrupt can't occur, which might try to access
 176          * user memory (to get a stack trace) and possible cause an STAB miss
 177          * which would update the stab_cache/stab_cache_ptr per-cpu variables.
 178          */
 179         hard_irq_disable();
 180
 181         offset = __get_cpu_var(stab_cache_ptr);
 182         if (offset <= NR_STAB_CACHE_ENTRIES) {
 183                 int i;
 184
 185                 for (i = 0; i < offset; i++) {
 186                         ste = stab + __get_cpu_var(stab_cache[i]);
 187                         ste->esid_data = 0; /* invalidate entry */
 188                 }
 189         } else {
 190                 unsigned long entry;
 191
 192                 /* Invalidate all entries. */
 193                 ste = stab;
 194
 195                 /* Never flush the first entry. */
 196                 ste += 1;
 197                 for (entry = 1;
 198                      entry < (HW_PAGE_SIZE / sizeof(struct stab_entry));
 199                      entry++, ste++) {
 200                         unsigned long ea;
 201                         ea = ste->esid_data & ESID_MASK;
 202                         if (!is_kernel_addr(ea)) {
 203                                 ste->esid_data = 0;
 204                         }
 205                 }
 206         }
 207
 208         asm volatile("sync; slbia; sync":::"memory");
 209
 210         __get_cpu_var(stab_cache_ptr) = 0;
 211
 212         /* Now preload some entries for the new task */
 213         if (test_tsk_thread_flag(tsk, TIF_32BIT))
 214                 unmapped_base = TASK_UNMAPPED_BASE_USER32;
 215         else
 216                 unmapped_base = TASK_UNMAPPED_BASE_USER64;
 217
 218         __ste_allocate(pc, mm);
 219
 220         if (GET_ESID(pc) == GET_ESID(stack))
 221                 return;
 222
 223         __ste_allocate(stack, mm);
 224
 225         if ((GET_ESID(pc) == GET_ESID(unmapped_base))
 226             || (GET_ESID(stack) == GET_ESID(unmapped_base)))
 227                 return;
 228
 229         __ste_allocate(unmapped_base, mm);
 230
 231         /* Order update */
 232         asm volatile("sync" : : : "memory");
 233 }
 234
 235 /*
 236  * Allocate segment tables for secondary CPUs.  These must all go in
 237  * the first (bolted) segment, so that do_stab_bolted won't get a
 238  * recursive segment miss on the segment table itself.
 239  */
 240 void __init stabs_alloc(void)
 241 {
 242         int cpu;
 243
 244         if (mmu_has_feature(MMU_FTR_SLB))
 245                 return;
 246
 247         for_each_possible_cpu(cpu) {
 248                 unsigned long newstab;
 249
 250                 if (cpu == 0)
 251                         continue; /* stab for CPU 0 is statically allocated */
 252
 253                 newstab = memblock_alloc_base(HW_PAGE_SIZE, HW_PAGE_SIZE,
 254                                          1<<SID_SHIFT);
 255                 newstab = (unsigned long)__va(newstab);
 256
 257                 memset((void *)newstab, 0, HW_PAGE_SIZE);
 258
 259                 paca[cpu].stab_addr = newstab;
 260                 paca[cpu].stab_real = virt_to_abs(newstab);
 261                 printk(KERN_INFO "Segment table for CPU %d at 0x%llx "
 262                        "virtual, 0x%llx absolute\n",
 263                        cpu, paca[cpu].stab_addr, paca[cpu].stab_real);
 264         }
 265 }
 266
 267 /*
 268  * Build an entry for the base kernel segment and put it into
 269  * the segment table or SLB.  All other segment table or SLB
 270  * entries are faulted in.
 271  */
 272 void stab_initialize(unsigned long stab)
 273 {
 274         unsigned long vsid = get_kernel_vsid(PAGE_OFFSET, MMU_SEGSIZE_256M);
 275         unsigned long stabreal;
 276
 277         asm volatile("isync; slbia; isync":::"memory");
 278         make_ste(stab, GET_ESID(PAGE_OFFSET), vsid);
 279
 280         /* Order update */
 281         asm volatile("sync":::"memory");
 282
 283         /* Set ASR */
 284         stabreal = get_paca()->stab_real | 0x1ul;
 285
 286         mtspr(SPRN_ASR, stabreal);
 287 }