1/* 2 * MMU context allocation for 64-bit kernels. 3 * 4 * Copyright (C) 2004 Anton Blanchard, IBM Corp. <anton@samba.org> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 * 11 */ 12 13#include <linux/sched.h> 14#include <linux/kernel.h> 15#include <linux/errno.h> 16#include <linux/string.h> 17#include <linux/types.h> 18#include <linux/mm.h> 19#include <linux/spinlock.h> 20#include <linux/idr.h> 21 22#include <asm/mmu_context.h> 23 24static DEFINE_SPINLOCK(mmu_context_lock); 25static DEFINE_IDR(mmu_context_idr); 26 27/* 28 * The proto-VSID space has 2^35 - 1 segments available for user mappings. 29 * Each segment contains 2^28 bytes. Each context maps 2^44 bytes, 30 * so we can support 2^19-1 contexts (19 == 35 + 28 - 44). 31 */ 32#define NO_CONTEXT 0 33#define MAX_CONTEXT ((1UL << 19) - 1) 34 35int init_new_context(struct task_struct *tsk, struct mm_struct *mm) 36{ 37 int index; 38 int err; 39 40again: 41 if (!idr_pre_get(&mmu_context_idr, GFP_KERNEL)) 42 return -ENOMEM; 43 44 spin_lock(&mmu_context_lock); 45 err = idr_get_new_above(&mmu_context_idr, NULL, 1, &index); 46 spin_unlock(&mmu_context_lock); 47 48 if (err == -EAGAIN) 49 goto again; 50 else if (err) 51 return err; 52 53 if (index > MAX_CONTEXT) { 54 spin_lock(&mmu_context_lock); 55 idr_remove(&mmu_context_idr, index); 56 spin_unlock(&mmu_context_lock); 57 return -ENOMEM; 58 } 59 60 /* The old code would re-promote on fork, we don't do that 61 * when using slices as it could cause problem promoting slices 62 * that have been forced down to 4K 63 */ 64 if (slice_mm_new_context(mm)) 65 slice_set_user_psize(mm, mmu_virtual_psize); 66 mm->context.id = index; 67 68 return 0; 69} 70 71void destroy_context(struct mm_struct *mm) 72{ 73 spin_lock(&mmu_context_lock); 74 idr_remove(&mmu_context_idr, mm->context.id); 75 spin_unlock(&mmu_context_lock); 76 77 mm->context.id = NO_CONTEXT; 78} 79