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stab.c

/*
 * PowerPC64 Segment Translation Support.
 *
 * Dave Engebretsen and Mike Corrigan {engebret|mikejc}@us.ibm.com
 *    Copyright (c) 2001 Dave Engebretsen
 *
 * Copyright (C) 2002 Anton Blanchard <anton@au.ibm.com>, IBM
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

#include <asm/pgtable.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/paca.h>
#include <asm/cputable.h>
#include <asm/lmb.h>
#include <asm/abs_addr.h>
#include <asm/firmware.h>
#include <asm/iseries/hv_call.h>

struct stab_entry {
      unsigned long esid_data;
      unsigned long vsid_data;
};

#define NR_STAB_CACHE_ENTRIES 8
DEFINE_PER_CPU(long, stab_cache_ptr);
DEFINE_PER_CPU(long, stab_cache[NR_STAB_CACHE_ENTRIES]);

/*
 * Create a segment table entry for the given esid/vsid pair.
 */
static int make_ste(unsigned long stab, unsigned long esid, unsigned long vsid)
{
      unsigned long esid_data, vsid_data;
      unsigned long entry, group, old_esid, castout_entry, i;
      unsigned int global_entry;
      struct stab_entry *ste, *castout_ste;
      unsigned long kernel_segment = (esid << SID_SHIFT) >= PAGE_OFFSET;

      vsid_data = vsid << STE_VSID_SHIFT;
      esid_data = esid << SID_SHIFT | STE_ESID_KP | STE_ESID_V;
      if (! kernel_segment)
            esid_data |= STE_ESID_KS;

      /* Search the primary group first. */
      global_entry = (esid & 0x1f) << 3;
      ste = (struct stab_entry *)(stab | ((esid & 0x1f) << 7));

      /* Find an empty entry, if one exists. */
      for (group = 0; group < 2; group++) {
            for (entry = 0; entry < 8; entry++, ste++) {
                  if (!(ste->esid_data & STE_ESID_V)) {
                        ste->vsid_data = vsid_data;
                        eieio();
                        ste->esid_data = esid_data;
                        return (global_entry | entry);
                  }
            }
            /* Now search the secondary group. */
            global_entry = ((~esid) & 0x1f) << 3;
            ste = (struct stab_entry *)(stab | (((~esid) & 0x1f) << 7));
      }

      /*
       * Could not find empty entry, pick one with a round robin selection.
       * Search all entries in the two groups.
       */
      castout_entry = get_paca()->stab_rr;
      for (i = 0; i < 16; i++) {
            if (castout_entry < 8) {
                  global_entry = (esid & 0x1f) << 3;
                  ste = (struct stab_entry *)(stab | ((esid & 0x1f) << 7));
                  castout_ste = ste + castout_entry;
            } else {
                  global_entry = ((~esid) & 0x1f) << 3;
                  ste = (struct stab_entry *)(stab | (((~esid) & 0x1f) << 7));
                  castout_ste = ste + (castout_entry - 8);
            }

            /* Dont cast out the first kernel segment */
            if ((castout_ste->esid_data & ESID_MASK) != PAGE_OFFSET)
                  break;

            castout_entry = (castout_entry + 1) & 0xf;
      }

      get_paca()->stab_rr = (castout_entry + 1) & 0xf;

      /* Modify the old entry to the new value. */

      /* Force previous translations to complete. DRENG */
      asm volatile("isync" : : : "memory");

      old_esid = castout_ste->esid_data >> SID_SHIFT;
      castout_ste->esid_data = 0;         /* Invalidate old entry */

      asm volatile("sync" : : : "memory");    /* Order update */

      castout_ste->vsid_data = vsid_data;
      eieio();                      /* Order update */
      castout_ste->esid_data = esid_data;

      asm volatile("slbie  %0" : : "r" (old_esid << SID_SHIFT));
      /* Ensure completion of slbie */
      asm volatile("sync" : : : "memory");

      return (global_entry | (castout_entry & 0x7));
}

/*
 * Allocate a segment table entry for the given ea and mm
 */
static int __ste_allocate(unsigned long ea, struct mm_struct *mm)
{
      unsigned long vsid;
      unsigned char stab_entry;
      unsigned long offset;

      /* Kernel or user address? */
      if (is_kernel_addr(ea)) {
            vsid = get_kernel_vsid(ea, MMU_SEGSIZE_256M);
      } else {
            if ((ea >= TASK_SIZE_USER64) || (! mm))
                  return 1;

            vsid = get_vsid(mm->context.id, ea, MMU_SEGSIZE_256M);
      }

      stab_entry = make_ste(get_paca()->stab_addr, GET_ESID(ea), vsid);

      if (!is_kernel_addr(ea)) {
            offset = __get_cpu_var(stab_cache_ptr);
            if (offset < NR_STAB_CACHE_ENTRIES)
                  __get_cpu_var(stab_cache[offset++]) = stab_entry;
            else
                  offset = NR_STAB_CACHE_ENTRIES+1;
            __get_cpu_var(stab_cache_ptr) = offset;

            /* Order update */
            asm volatile("sync":::"memory");
      }

      return 0;
}

int ste_allocate(unsigned long ea)
{
      return __ste_allocate(ea, current->mm);
}

/*
 * Do the segment table work for a context switch: flush all user
 * entries from the table, then preload some probably useful entries
 * for the new task
 */
void switch_stab(struct task_struct *tsk, struct mm_struct *mm)
{
      struct stab_entry *stab = (struct stab_entry *) get_paca()->stab_addr;
      struct stab_entry *ste;
      unsigned long offset = __get_cpu_var(stab_cache_ptr);
      unsigned long pc = KSTK_EIP(tsk);
      unsigned long stack = KSTK_ESP(tsk);
      unsigned long unmapped_base;

      /* Force previous translations to complete. DRENG */
      asm volatile("isync" : : : "memory");

      if (offset <= NR_STAB_CACHE_ENTRIES) {
            int i;

            for (i = 0; i < offset; i++) {
                  ste = stab + __get_cpu_var(stab_cache[i]);
                  ste->esid_data = 0; /* invalidate entry */
            }
      } else {
            unsigned long entry;

            /* Invalidate all entries. */
            ste = stab;

            /* Never flush the first entry. */
            ste += 1;
            for (entry = 1;
                 entry < (HW_PAGE_SIZE / sizeof(struct stab_entry));
                 entry++, ste++) {
                  unsigned long ea;
                  ea = ste->esid_data & ESID_MASK;
                  if (!is_kernel_addr(ea)) {
                        ste->esid_data = 0;
                  }
            }
      }

      asm volatile("sync; slbia; sync":::"memory");

      __get_cpu_var(stab_cache_ptr) = 0;

      /* Now preload some entries for the new task */
      if (test_tsk_thread_flag(tsk, TIF_32BIT))
            unmapped_base = TASK_UNMAPPED_BASE_USER32;
      else
            unmapped_base = TASK_UNMAPPED_BASE_USER64;

      __ste_allocate(pc, mm);

      if (GET_ESID(pc) == GET_ESID(stack))
            return;

      __ste_allocate(stack, mm);

      if ((GET_ESID(pc) == GET_ESID(unmapped_base))
          || (GET_ESID(stack) == GET_ESID(unmapped_base)))
            return;

      __ste_allocate(unmapped_base, mm);

      /* Order update */
      asm volatile("sync" : : : "memory");
}

/*
 * Allocate segment tables for secondary CPUs.  These must all go in
 * the first (bolted) segment, so that do_stab_bolted won't get a
 * recursive segment miss on the segment table itself.
 */
void __init stabs_alloc(void)
{
      int cpu;

      if (cpu_has_feature(CPU_FTR_SLB))
            return;

      for_each_possible_cpu(cpu) {
            unsigned long newstab;

            if (cpu == 0)
                  continue; /* stab for CPU 0 is statically allocated */

            newstab = lmb_alloc_base(HW_PAGE_SIZE, HW_PAGE_SIZE,
                               1<<SID_SHIFT);
            newstab = (unsigned long)__va(newstab);

            memset((void *)newstab, 0, HW_PAGE_SIZE);

            paca[cpu].stab_addr = newstab;
            paca[cpu].stab_real = virt_to_abs(newstab);
            printk(KERN_INFO "Segment table for CPU %d at 0x%lx "
                   "virtual, 0x%lx absolute\n",
                   cpu, paca[cpu].stab_addr, paca[cpu].stab_real);
      }
}

/*
 * Build an entry for the base kernel segment and put it into
 * the segment table or SLB.  All other segment table or SLB
 * entries are faulted in.
 */
void stab_initialize(unsigned long stab)
{
      unsigned long vsid = get_kernel_vsid(PAGE_OFFSET, MMU_SEGSIZE_256M);
      unsigned long stabreal;

      asm volatile("isync; slbia; isync":::"memory");
      make_ste(stab, GET_ESID(PAGE_OFFSET), vsid);

      /* Order update */
      asm volatile("sync":::"memory");

      /* Set ASR */
      stabreal = get_paca()->stab_real | 0x1ul;

#ifdef CONFIG_PPC_ISERIES
      if (firmware_has_feature(FW_FEATURE_ISERIES)) {
            HvCall1(HvCallBaseSetASR, stabreal);
            return;
      }
#endif /* CONFIG_PPC_ISERIES */

      mtspr(SPRN_ASR, stabreal);
}

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