mmu_context_hash32.rar_Free!

/* * 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, * 8260, and POWER3 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> #include <asm/tlbflush.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; }