arch/frv/mm/mmu-context.c

   1 /* mmu-context.c: MMU context allocation and management
   2  *
   3  * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   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 #include <linux/sched.h>
  13 #include <linux/mm.h>
  14 #include <asm/tlbflush.h>
  15
  16 #define NR_CXN  4096
  17
  18 static unsigned long cxn_bitmap[NR_CXN / (sizeof(unsigned long) * 8)];
  19 static LIST_HEAD(cxn_owners_lru);
  20 static DEFINE_SPINLOCK(cxn_owners_lock);
  21
  22 int __nongpreldata cxn_pinned = -1;
  23
  24
  25 /*****************************************************************************/
  26 /*
  27  * initialise a new context
  28  */
  29 int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
  30 {
  31         memset(&mm->context, 0, sizeof(mm->context));
  32         INIT_LIST_HEAD(&mm->context.id_link);
  33         mm->context.itlb_cached_pge = 0xffffffffUL;
  34         mm->context.dtlb_cached_pge = 0xffffffffUL;
  35
  36         return 0;
  37 } /* end init_new_context() */
  38
  39 /*****************************************************************************/
  40 /*
  41  * make sure a kernel MMU context has a CPU context number
  42  * - call with cxn_owners_lock held
  43  */
  44 static unsigned get_cxn(mm_context_t *ctx)
  45 {
  46         struct list_head *_p;
  47         mm_context_t *p;
  48         unsigned cxn;
  49
  50         if (!list_empty(&ctx->id_link)) {
  51                 list_move_tail(&ctx->id_link, &cxn_owners_lru);
  52         }
  53         else {
  54                 /* find the first unallocated context number
  55                  * - 0 is reserved for the kernel
  56                  */
  57                 cxn = find_next_zero_bit(cxn_bitmap, NR_CXN, 1);
  58                 if (cxn < NR_CXN) {
  59                         set_bit(cxn, cxn_bitmap);
  60                 }
  61                 else {
  62                         /* none remaining - need to steal someone else's cxn */
  63                         p = NULL;
  64                         list_for_each(_p, &cxn_owners_lru) {
  65                                 p = list_entry(_p, mm_context_t, id_link);
  66                                 if (!p->id_busy && p->id != cxn_pinned)
  67                                         break;
  68                         }
  69
  70                         BUG_ON(_p == &cxn_owners_lru);
  71
  72                         cxn = p->id;
  73                         p->id = 0;
  74                         list_del_init(&p->id_link);
  75                         __flush_tlb_mm(cxn);
  76                 }
  77
  78                 ctx->id = cxn;
  79                 list_add_tail(&ctx->id_link, &cxn_owners_lru);
  80         }
  81
  82         return ctx->id;
  83 } /* end get_cxn() */
  84
  85 /*****************************************************************************/
  86 /*
  87  * restore the current TLB miss handler mapped page tables into the MMU context and set up a
  88  * mapping for the page directory
  89  */
  90 void change_mm_context(mm_context_t *old, mm_context_t *ctx, pgd_t *pgd)
  91 {
  92         unsigned long _pgd;
  93
  94         _pgd = virt_to_phys(pgd);
  95
  96         /* save the state of the outgoing MMU context */
  97         old->id_busy = 0;
  98
  99         asm volatile("movsg scr0,%0"   : "=r"(old->itlb_cached_pge));
 100         asm volatile("movsg dampr4,%0" : "=r"(old->itlb_ptd_mapping));
 101         asm volatile("movsg scr1,%0"   : "=r"(old->dtlb_cached_pge));
 102         asm volatile("movsg dampr5,%0" : "=r"(old->dtlb_ptd_mapping));
 103
 104         /* select an MMU context number */
 105         spin_lock(&cxn_owners_lock);
 106         get_cxn(ctx);
 107         ctx->id_busy = 1;
 108         spin_unlock(&cxn_owners_lock);
 109
 110         asm volatile("movgs %0,cxnr"   : : "r"(ctx->id));
 111
 112         /* restore the state of the incoming MMU context */
 113         asm volatile("movgs %0,scr0"   : : "r"(ctx->itlb_cached_pge));
 114         asm volatile("movgs %0,dampr4" : : "r"(ctx->itlb_ptd_mapping));
 115         asm volatile("movgs %0,scr1"   : : "r"(ctx->dtlb_cached_pge));
 116         asm volatile("movgs %0,dampr5" : : "r"(ctx->dtlb_ptd_mapping));
 117
 118         /* map the PGD into uncached virtual memory */
 119         asm volatile("movgs %0,ttbr"   : : "r"(_pgd));
 120         asm volatile("movgs %0,dampr3"
 121                      :: "r"(_pgd | xAMPRx_L | xAMPRx_M | xAMPRx_SS_16Kb |
 122                             xAMPRx_S | xAMPRx_C | xAMPRx_V));
 123
 124 } /* end change_mm_context() */
 125
 126 /*****************************************************************************/
 127 /*
 128  * finished with an MMU context number
 129  */
 130 void destroy_context(struct mm_struct *mm)
 131 {
 132         mm_context_t *ctx = &mm->context;
 133
 134         spin_lock(&cxn_owners_lock);
 135
 136         if (!list_empty(&ctx->id_link)) {
 137                 if (ctx->id == cxn_pinned)
 138                         cxn_pinned = -1;
 139
 140                 list_del_init(&ctx->id_link);
 141                 clear_bit(ctx->id, cxn_bitmap);
 142                 __flush_tlb_mm(ctx->id);
 143                 ctx->id = 0;
 144         }
 145
 146         spin_unlock(&cxn_owners_lock);
 147 } /* end destroy_context() */
 148
 149 /*****************************************************************************/
 150 /*
 151  * display the MMU context currently a process is currently using
 152  */
 153 #ifdef CONFIG_PROC_FS
 154 char *proc_pid_status_frv_cxnr(struct mm_struct *mm, char *buffer)
 155 {
 156         spin_lock(&cxn_owners_lock);
 157         buffer += sprintf(buffer, "CXNR: %u\n", mm->context.id);
 158         spin_unlock(&cxn_owners_lock);
 159
 160         return buffer;
 161 } /* end proc_pid_status_frv_cxnr() */
 162 #endif
 163
 164 /*****************************************************************************/
 165 /*
 166  * (un)pin a process's mm_struct's MMU context ID
 167  */
 168 int cxn_pin_by_pid(pid_t pid)
 169 {
 170         struct task_struct *tsk;
 171         struct mm_struct *mm = NULL;
 172         int ret;
 173
 174         /* unpin if pid is zero */
 175         if (pid == 0) {
 176                 cxn_pinned = -1;
 177                 return 0;
 178         }
 179
 180         ret = -ESRCH;
 181
 182         /* get a handle on the mm_struct */
 183         read_lock(&tasklist_lock);
 184         tsk = find_task_by_pid(pid);
 185         if (tsk) {
 186                 ret = -EINVAL;
 187
 188                 task_lock(tsk);
 189                 if (tsk->mm) {
 190                         mm = tsk->mm;
 191                         atomic_inc(&mm->mm_users);
 192                         ret = 0;
 193                 }
 194                 task_unlock(tsk);
 195         }
 196         read_unlock(&tasklist_lock);
 197
 198         if (ret < 0)
 199                 return ret;
 200
 201         /* make sure it has a CXN and pin it */
 202         spin_lock(&cxn_owners_lock);
 203         cxn_pinned = get_cxn(&mm->context);
 204         spin_unlock(&cxn_owners_lock);
 205
 206         mmput(mm);
 207         return 0;
 208 } /* end cxn_pin_by_pid() */