119 lines
3.4 KiB
C
119 lines
3.4 KiB
C
/*
|
|
* This file contains the routines for handling the MMU on those
|
|
* PowerPC implementations where the MMU substantially follows the
|
|
* architecture specification. This includes the 6xx, 7xx, 7xxx,
|
|
* and 8260 implementations but excludes the 8xx and 4xx.
|
|
* -- paulus
|
|
*
|
|
* Derived from arch/ppc/mm/init.c:
|
|
* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
|
|
*
|
|
* Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
|
|
* and Cort Dougan (PReP) (cort@cs.nmt.edu)
|
|
* Copyright (C) 1996 Paul Mackerras
|
|
*
|
|
* Derived from "arch/i386/mm/init.c"
|
|
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
|
|
*
|
|
* 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 <linux/mm.h>
|
|
#include <linux/init.h>
|
|
#include <linux/export.h>
|
|
|
|
#include <asm/mmu_context.h>
|
|
|
|
/*
|
|
* On 32-bit PowerPC 6xx/7xx/7xxx CPUs, we use a set of 16 VSIDs
|
|
* (virtual segment identifiers) for each context. Although the
|
|
* hardware supports 24-bit VSIDs, and thus >1 million contexts,
|
|
* we only use 32,768 of them. That is ample, since there can be
|
|
* at most around 30,000 tasks in the system anyway, and it means
|
|
* that we can use a bitmap to indicate which contexts are in use.
|
|
* Using a bitmap means that we entirely avoid all of the problems
|
|
* that we used to have when the context number overflowed,
|
|
* particularly on SMP systems.
|
|
* -- paulus.
|
|
*/
|
|
#define NO_CONTEXT ((unsigned long) -1)
|
|
#define LAST_CONTEXT 32767
|
|
#define FIRST_CONTEXT 1
|
|
|
|
/*
|
|
* This function defines the mapping from contexts to VSIDs (virtual
|
|
* segment IDs). We use a skew on both the context and the high 4 bits
|
|
* of the 32-bit virtual address (the "effective segment ID") in order
|
|
* to spread out the entries in the MMU hash table. Note, if this
|
|
* function is changed then arch/ppc/mm/hashtable.S will have to be
|
|
* changed to correspond.
|
|
*
|
|
*
|
|
* CTX_TO_VSID(ctx, va) (((ctx) * (897 * 16) + ((va) >> 28) * 0x111) \
|
|
* & 0xffffff)
|
|
*/
|
|
|
|
static unsigned long next_mmu_context;
|
|
static unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
|
|
|
|
unsigned long __init_new_context(void)
|
|
{
|
|
unsigned long ctx = next_mmu_context;
|
|
|
|
while (test_and_set_bit(ctx, context_map)) {
|
|
ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
|
|
if (ctx > LAST_CONTEXT)
|
|
ctx = 0;
|
|
}
|
|
next_mmu_context = (ctx + 1) & LAST_CONTEXT;
|
|
|
|
return ctx;
|
|
}
|
|
EXPORT_SYMBOL_GPL(__init_new_context);
|
|
|
|
/*
|
|
* Set up the context for a new address space.
|
|
*/
|
|
int init_new_context(struct task_struct *t, struct mm_struct *mm)
|
|
{
|
|
mm->context.id = __init_new_context();
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Free a context ID. Make sure to call this with preempt disabled!
|
|
*/
|
|
void __destroy_context(unsigned long ctx)
|
|
{
|
|
clear_bit(ctx, context_map);
|
|
}
|
|
EXPORT_SYMBOL_GPL(__destroy_context);
|
|
|
|
/*
|
|
* We're finished using the context for an address space.
|
|
*/
|
|
void destroy_context(struct mm_struct *mm)
|
|
{
|
|
preempt_disable();
|
|
if (mm->context.id != NO_CONTEXT) {
|
|
__destroy_context(mm->context.id);
|
|
mm->context.id = NO_CONTEXT;
|
|
}
|
|
preempt_enable();
|
|
}
|
|
|
|
/*
|
|
* Initialize the context management stuff.
|
|
*/
|
|
void __init mmu_context_init(void)
|
|
{
|
|
/* Reserve context 0 for kernel use */
|
|
context_map[0] = (1 << FIRST_CONTEXT) - 1;
|
|
next_mmu_context = FIRST_CONTEXT;
|
|
}
|