2008-12-18 20:13:24 +01:00
|
|
|
/*
|
|
|
|
* This file contains the routines for handling the MMU on those
|
|
|
|
* PowerPC implementations where the MMU is not using the hash
|
|
|
|
* table, such as 8xx, 4xx, BookE's etc...
|
|
|
|
*
|
|
|
|
* Copyright 2008 Ben Herrenschmidt <benh@kernel.crashing.org>
|
|
|
|
* IBM Corp.
|
|
|
|
*
|
|
|
|
* Derived from previous arch/powerpc/mm/mmu_context.c
|
|
|
|
* and arch/powerpc/include/asm/mmu_context.h
|
|
|
|
*
|
|
|
|
* 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.
|
|
|
|
*
|
2008-12-18 20:13:29 +01:00
|
|
|
* TODO:
|
|
|
|
*
|
|
|
|
* - The global context lock will not scale very well
|
|
|
|
* - The maps should be dynamically allocated to allow for processors
|
|
|
|
* that support more PID bits at runtime
|
|
|
|
* - Implement flush_tlb_mm() by making the context stale and picking
|
|
|
|
* a new one
|
|
|
|
* - More aggressively clear stale map bits and maybe find some way to
|
|
|
|
* also clear mm->cpu_vm_mask bits when processes are migrated
|
2008-12-18 20:13:24 +01:00
|
|
|
*/
|
|
|
|
|
2008-12-18 20:13:29 +01:00
|
|
|
#undef DEBUG
|
|
|
|
#define DEBUG_STEAL_ONLY
|
|
|
|
#undef DEBUG_MAP_CONSISTENCY
|
2008-12-18 20:13:48 +01:00
|
|
|
/*#define DEBUG_CLAMP_LAST_CONTEXT 15 */
|
2008-12-18 20:13:29 +01:00
|
|
|
|
|
|
|
#include <linux/kernel.h>
|
2008-12-18 20:13:24 +01:00
|
|
|
#include <linux/mm.h>
|
|
|
|
#include <linux/init.h>
|
2008-12-18 20:13:48 +01:00
|
|
|
#include <linux/spinlock.h>
|
|
|
|
#include <linux/bootmem.h>
|
|
|
|
#include <linux/notifier.h>
|
|
|
|
#include <linux/cpu.h>
|
2008-12-18 20:13:24 +01:00
|
|
|
|
|
|
|
#include <asm/mmu_context.h>
|
|
|
|
#include <asm/tlbflush.h>
|
|
|
|
|
2008-12-18 20:13:48 +01:00
|
|
|
static unsigned int first_context, last_context;
|
2008-12-18 20:13:29 +01:00
|
|
|
static unsigned int next_context, nr_free_contexts;
|
2008-12-18 20:13:48 +01:00
|
|
|
static unsigned long *context_map;
|
|
|
|
static unsigned long *stale_map[NR_CPUS];
|
|
|
|
static struct mm_struct **context_mm;
|
2008-12-18 20:13:29 +01:00
|
|
|
static spinlock_t context_lock = SPIN_LOCK_UNLOCKED;
|
2008-12-18 20:13:24 +01:00
|
|
|
|
2008-12-18 20:13:48 +01:00
|
|
|
#define CTX_MAP_SIZE \
|
|
|
|
(sizeof(unsigned long) * (last_context / BITS_PER_LONG + 1))
|
|
|
|
|
|
|
|
|
2008-12-18 20:13:24 +01:00
|
|
|
/* Steal a context from a task that has one at the moment.
|
2008-12-18 20:13:29 +01:00
|
|
|
*
|
|
|
|
* This is used when we are running out of available PID numbers
|
|
|
|
* on the processors.
|
|
|
|
*
|
2008-12-18 20:13:24 +01:00
|
|
|
* This isn't an LRU system, it just frees up each context in
|
|
|
|
* turn (sort-of pseudo-random replacement :). This would be the
|
|
|
|
* place to implement an LRU scheme if anyone was motivated to do it.
|
|
|
|
* -- paulus
|
2008-12-18 20:13:29 +01:00
|
|
|
*
|
|
|
|
* For context stealing, we use a slightly different approach for
|
|
|
|
* SMP and UP. Basically, the UP one is simpler and doesn't use
|
|
|
|
* the stale map as we can just flush the local CPU
|
|
|
|
* -- benh
|
2008-12-18 20:13:24 +01:00
|
|
|
*/
|
2008-12-18 20:13:29 +01:00
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
static unsigned int steal_context_smp(unsigned int id)
|
2008-12-18 20:13:24 +01:00
|
|
|
{
|
|
|
|
struct mm_struct *mm;
|
2008-12-18 20:13:29 +01:00
|
|
|
unsigned int cpu, max;
|
2008-12-18 20:13:24 +01:00
|
|
|
|
2008-12-18 20:13:48 +01:00
|
|
|
max = last_context - first_context;
|
2008-12-18 20:13:24 +01:00
|
|
|
|
2008-12-18 20:13:29 +01:00
|
|
|
/* Attempt to free next_context first and then loop until we manage */
|
|
|
|
while (max--) {
|
|
|
|
/* Pick up the victim mm */
|
|
|
|
mm = context_mm[id];
|
2008-12-18 20:13:24 +01:00
|
|
|
|
2008-12-18 20:13:29 +01:00
|
|
|
/* We have a candidate victim, check if it's active, on SMP
|
|
|
|
* we cannot steal active contexts
|
|
|
|
*/
|
|
|
|
if (mm->context.active) {
|
|
|
|
id++;
|
2008-12-18 20:13:48 +01:00
|
|
|
if (id > last_context)
|
|
|
|
id = first_context;
|
2008-12-18 20:13:29 +01:00
|
|
|
continue;
|
|
|
|
}
|
|
|
|
pr_debug("[%d] steal context %d from mm @%p\n",
|
|
|
|
smp_processor_id(), id, mm);
|
|
|
|
|
|
|
|
/* Mark this mm has having no context anymore */
|
|
|
|
mm->context.id = MMU_NO_CONTEXT;
|
|
|
|
|
|
|
|
/* Mark it stale on all CPUs that used this mm */
|
2009-03-15 19:16:43 +01:00
|
|
|
for_each_cpu(cpu, mm_cpumask(mm))
|
2008-12-18 20:13:29 +01:00
|
|
|
__set_bit(id, stale_map[cpu]);
|
|
|
|
return id;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* This will happen if you have more CPUs than available contexts,
|
|
|
|
* all we can do here is wait a bit and try again
|
|
|
|
*/
|
|
|
|
spin_unlock(&context_lock);
|
|
|
|
cpu_relax();
|
|
|
|
spin_lock(&context_lock);
|
2009-05-19 18:56:42 +02:00
|
|
|
|
|
|
|
/* This will cause the caller to try again */
|
|
|
|
return MMU_NO_CONTEXT;
|
2008-12-18 20:13:29 +01:00
|
|
|
}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
|
|
|
|
/* Note that this will also be called on SMP if all other CPUs are
|
|
|
|
* offlined, which means that it may be called for cpu != 0. For
|
|
|
|
* this to work, we somewhat assume that CPUs that are onlined
|
|
|
|
* come up with a fully clean TLB (or are cleaned when offlined)
|
2008-12-18 20:13:24 +01:00
|
|
|
*/
|
2008-12-18 20:13:29 +01:00
|
|
|
static unsigned int steal_context_up(unsigned int id)
|
2008-12-18 20:13:24 +01:00
|
|
|
{
|
2008-12-18 20:13:29 +01:00
|
|
|
struct mm_struct *mm;
|
|
|
|
int cpu = smp_processor_id();
|
2008-12-18 20:13:24 +01:00
|
|
|
|
2008-12-18 20:13:29 +01:00
|
|
|
/* Pick up the victim mm */
|
|
|
|
mm = context_mm[id];
|
|
|
|
|
|
|
|
pr_debug("[%d] steal context %d from mm @%p\n", cpu, id, mm);
|
2008-12-18 20:13:24 +01:00
|
|
|
|
2008-12-18 20:13:29 +01:00
|
|
|
/* Flush the TLB for that context */
|
|
|
|
local_flush_tlb_mm(mm);
|
|
|
|
|
2009-05-24 17:33:34 +02:00
|
|
|
/* Mark this mm has having no context anymore */
|
|
|
|
mm->context.id = MMU_NO_CONTEXT;
|
|
|
|
|
2008-12-18 20:13:29 +01:00
|
|
|
/* XXX This clear should ultimately be part of local_flush_tlb_mm */
|
|
|
|
__clear_bit(id, stale_map[cpu]);
|
|
|
|
|
|
|
|
return id;
|
|
|
|
}
|
|
|
|
|
|
|
|
#ifdef DEBUG_MAP_CONSISTENCY
|
|
|
|
static void context_check_map(void)
|
|
|
|
{
|
|
|
|
unsigned int id, nrf, nact;
|
|
|
|
|
|
|
|
nrf = nact = 0;
|
2008-12-18 20:13:48 +01:00
|
|
|
for (id = first_context; id <= last_context; id++) {
|
2008-12-18 20:13:29 +01:00
|
|
|
int used = test_bit(id, context_map);
|
|
|
|
if (!used)
|
|
|
|
nrf++;
|
|
|
|
if (used != (context_mm[id] != NULL))
|
|
|
|
pr_err("MMU: Context %d is %s and MM is %p !\n",
|
|
|
|
id, used ? "used" : "free", context_mm[id]);
|
|
|
|
if (context_mm[id] != NULL)
|
|
|
|
nact += context_mm[id]->context.active;
|
2008-12-18 20:13:24 +01:00
|
|
|
}
|
2008-12-18 20:13:29 +01:00
|
|
|
if (nrf != nr_free_contexts) {
|
|
|
|
pr_err("MMU: Free context count out of sync ! (%d vs %d)\n",
|
|
|
|
nr_free_contexts, nrf);
|
|
|
|
nr_free_contexts = nrf;
|
|
|
|
}
|
|
|
|
if (nact > num_online_cpus())
|
|
|
|
pr_err("MMU: More active contexts than CPUs ! (%d vs %d)\n",
|
|
|
|
nact, num_online_cpus());
|
2008-12-18 20:13:48 +01:00
|
|
|
if (first_context > 0 && !test_bit(0, context_map))
|
|
|
|
pr_err("MMU: Context 0 has been freed !!!\n");
|
2008-12-18 20:13:24 +01:00
|
|
|
}
|
2008-12-18 20:13:29 +01:00
|
|
|
#else
|
|
|
|
static void context_check_map(void) { }
|
|
|
|
#endif
|
2008-12-18 20:13:24 +01:00
|
|
|
|
|
|
|
void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next)
|
|
|
|
{
|
2008-12-18 20:13:29 +01:00
|
|
|
unsigned int id, cpu = smp_processor_id();
|
|
|
|
unsigned long *map;
|
2008-12-18 20:13:24 +01:00
|
|
|
|
2008-12-18 20:13:29 +01:00
|
|
|
/* No lockless fast path .. yet */
|
|
|
|
spin_lock(&context_lock);
|
|
|
|
|
|
|
|
#ifndef DEBUG_STEAL_ONLY
|
|
|
|
pr_debug("[%d] activating context for mm @%p, active=%d, id=%d\n",
|
|
|
|
cpu, next, next->context.active, next->context.id);
|
|
|
|
#endif
|
|
|
|
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
/* Mark us active and the previous one not anymore */
|
|
|
|
next->context.active++;
|
|
|
|
if (prev) {
|
2008-12-18 20:13:48 +01:00
|
|
|
#ifndef DEBUG_STEAL_ONLY
|
|
|
|
pr_debug(" old context %p active was: %d\n",
|
|
|
|
prev, prev->context.active);
|
|
|
|
#endif
|
2008-12-18 20:13:29 +01:00
|
|
|
WARN_ON(prev->context.active < 1);
|
|
|
|
prev->context.active--;
|
|
|
|
}
|
2009-05-19 18:56:42 +02:00
|
|
|
|
|
|
|
again:
|
2008-12-18 20:13:29 +01:00
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
|
|
|
|
/* If we already have a valid assigned context, skip all that */
|
|
|
|
id = next->context.id;
|
|
|
|
if (likely(id != MMU_NO_CONTEXT))
|
|
|
|
goto ctxt_ok;
|
|
|
|
|
|
|
|
/* We really don't have a context, let's try to acquire one */
|
|
|
|
id = next_context;
|
2008-12-18 20:13:48 +01:00
|
|
|
if (id > last_context)
|
|
|
|
id = first_context;
|
2008-12-18 20:13:29 +01:00
|
|
|
map = context_map;
|
|
|
|
|
|
|
|
/* No more free contexts, let's try to steal one */
|
|
|
|
if (nr_free_contexts == 0) {
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
if (num_online_cpus() > 1) {
|
|
|
|
id = steal_context_smp(id);
|
2009-05-19 18:56:42 +02:00
|
|
|
if (id == MMU_NO_CONTEXT)
|
|
|
|
goto again;
|
2008-12-18 20:13:29 +01:00
|
|
|
}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
id = steal_context_up(id);
|
|
|
|
goto stolen;
|
|
|
|
}
|
|
|
|
nr_free_contexts--;
|
|
|
|
|
|
|
|
/* We know there's at least one free context, try to find it */
|
|
|
|
while (__test_and_set_bit(id, map)) {
|
2008-12-18 20:13:48 +01:00
|
|
|
id = find_next_zero_bit(map, last_context+1, id);
|
|
|
|
if (id > last_context)
|
|
|
|
id = first_context;
|
2008-12-18 20:13:29 +01:00
|
|
|
}
|
|
|
|
stolen:
|
|
|
|
next_context = id + 1;
|
|
|
|
context_mm[id] = next;
|
|
|
|
next->context.id = id;
|
|
|
|
|
|
|
|
#ifndef DEBUG_STEAL_ONLY
|
|
|
|
pr_debug("[%d] picked up new id %d, nrf is now %d\n",
|
|
|
|
cpu, id, nr_free_contexts);
|
|
|
|
#endif
|
|
|
|
|
|
|
|
context_check_map();
|
|
|
|
ctxt_ok:
|
|
|
|
|
|
|
|
/* If that context got marked stale on this CPU, then flush the
|
|
|
|
* local TLB for it and unmark it before we use it
|
|
|
|
*/
|
|
|
|
if (test_bit(id, stale_map[cpu])) {
|
|
|
|
pr_debug("[%d] flushing stale context %d for mm @%p !\n",
|
|
|
|
cpu, id, next);
|
|
|
|
local_flush_tlb_mm(next);
|
|
|
|
|
|
|
|
/* XXX This clear should ultimately be part of local_flush_tlb_mm */
|
|
|
|
__clear_bit(id, stale_map[cpu]);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Flick the MMU and release lock */
|
|
|
|
set_context(id, next->pgd);
|
|
|
|
spin_unlock(&context_lock);
|
2008-12-18 20:13:24 +01:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Set up the context for a new address space.
|
|
|
|
*/
|
|
|
|
int init_new_context(struct task_struct *t, struct mm_struct *mm)
|
|
|
|
{
|
2008-12-18 20:13:29 +01:00
|
|
|
mm->context.id = MMU_NO_CONTEXT;
|
|
|
|
mm->context.active = 0;
|
|
|
|
|
2008-12-18 20:13:24 +01:00
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* We're finished using the context for an address space.
|
|
|
|
*/
|
|
|
|
void destroy_context(struct mm_struct *mm)
|
|
|
|
{
|
2008-12-18 20:13:29 +01:00
|
|
|
unsigned int id;
|
|
|
|
|
|
|
|
if (mm->context.id == MMU_NO_CONTEXT)
|
|
|
|
return;
|
|
|
|
|
|
|
|
WARN_ON(mm->context.active != 0);
|
|
|
|
|
|
|
|
spin_lock(&context_lock);
|
|
|
|
id = mm->context.id;
|
|
|
|
if (id != MMU_NO_CONTEXT) {
|
|
|
|
__clear_bit(id, context_map);
|
|
|
|
mm->context.id = MMU_NO_CONTEXT;
|
|
|
|
#ifdef DEBUG_MAP_CONSISTENCY
|
|
|
|
mm->context.active = 0;
|
|
|
|
#endif
|
2009-05-19 18:56:42 +02:00
|
|
|
context_mm[id] = NULL;
|
2008-12-18 20:13:29 +01:00
|
|
|
nr_free_contexts++;
|
2008-12-18 20:13:24 +01:00
|
|
|
}
|
2008-12-18 20:13:29 +01:00
|
|
|
spin_unlock(&context_lock);
|
2008-12-18 20:13:24 +01:00
|
|
|
}
|
|
|
|
|
2008-12-18 20:13:48 +01:00
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
|
|
|
|
static int __cpuinit mmu_context_cpu_notify(struct notifier_block *self,
|
|
|
|
unsigned long action, void *hcpu)
|
|
|
|
{
|
|
|
|
unsigned int cpu = (unsigned int)(long)hcpu;
|
|
|
|
|
|
|
|
/* We don't touch CPU 0 map, it's allocated at aboot and kept
|
|
|
|
* around forever
|
|
|
|
*/
|
|
|
|
if (cpu == 0)
|
|
|
|
return NOTIFY_OK;
|
|
|
|
|
|
|
|
switch (action) {
|
|
|
|
case CPU_ONLINE:
|
|
|
|
case CPU_ONLINE_FROZEN:
|
|
|
|
pr_debug("MMU: Allocating stale context map for CPU %d\n", cpu);
|
|
|
|
stale_map[cpu] = kzalloc(CTX_MAP_SIZE, GFP_KERNEL);
|
|
|
|
break;
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
|
|
case CPU_DEAD:
|
|
|
|
case CPU_DEAD_FROZEN:
|
|
|
|
pr_debug("MMU: Freeing stale context map for CPU %d\n", cpu);
|
|
|
|
kfree(stale_map[cpu]);
|
|
|
|
stale_map[cpu] = NULL;
|
|
|
|
break;
|
|
|
|
#endif
|
|
|
|
}
|
|
|
|
return NOTIFY_OK;
|
|
|
|
}
|
|
|
|
|
|
|
|
static struct notifier_block __cpuinitdata mmu_context_cpu_nb = {
|
|
|
|
.notifier_call = mmu_context_cpu_notify,
|
|
|
|
};
|
|
|
|
|
|
|
|
#endif /* CONFIG_SMP */
|
2008-12-18 20:13:24 +01:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Initialize the context management stuff.
|
|
|
|
*/
|
|
|
|
void __init mmu_context_init(void)
|
|
|
|
{
|
2008-12-18 20:13:29 +01:00
|
|
|
/* Mark init_mm as being active on all possible CPUs since
|
|
|
|
* we'll get called with prev == init_mm the first time
|
|
|
|
* we schedule on a given CPU
|
|
|
|
*/
|
|
|
|
init_mm.context.active = NR_CPUS;
|
|
|
|
|
2008-12-18 20:13:48 +01:00
|
|
|
/*
|
|
|
|
* The MPC8xx has only 16 contexts. We rotate through them on each
|
|
|
|
* task switch. A better way would be to keep track of tasks that
|
|
|
|
* own contexts, and implement an LRU usage. That way very active
|
|
|
|
* tasks don't always have to pay the TLB reload overhead. The
|
|
|
|
* kernel pages are mapped shared, so the kernel can run on behalf
|
|
|
|
* of any task that makes a kernel entry. Shared does not mean they
|
|
|
|
* are not protected, just that the ASID comparison is not performed.
|
|
|
|
* -- Dan
|
|
|
|
*
|
|
|
|
* The IBM4xx has 256 contexts, so we can just rotate through these
|
|
|
|
* as a way of "switching" contexts. If the TID of the TLB is zero,
|
|
|
|
* the PID/TID comparison is disabled, so we can use a TID of zero
|
|
|
|
* to represent all kernel pages as shared among all contexts.
|
|
|
|
* -- Dan
|
|
|
|
*/
|
|
|
|
if (mmu_has_feature(MMU_FTR_TYPE_8xx)) {
|
|
|
|
first_context = 0;
|
|
|
|
last_context = 15;
|
|
|
|
} else {
|
|
|
|
first_context = 1;
|
|
|
|
last_context = 255;
|
|
|
|
}
|
|
|
|
|
|
|
|
#ifdef DEBUG_CLAMP_LAST_CONTEXT
|
|
|
|
last_context = DEBUG_CLAMP_LAST_CONTEXT;
|
|
|
|
#endif
|
|
|
|
/*
|
|
|
|
* Allocate the maps used by context management
|
|
|
|
*/
|
|
|
|
context_map = alloc_bootmem(CTX_MAP_SIZE);
|
|
|
|
context_mm = alloc_bootmem(sizeof(void *) * (last_context + 1));
|
|
|
|
stale_map[0] = alloc_bootmem(CTX_MAP_SIZE);
|
|
|
|
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
register_cpu_notifier(&mmu_context_cpu_nb);
|
|
|
|
#endif
|
|
|
|
|
|
|
|
printk(KERN_INFO
|
2009-03-19 20:34:13 +01:00
|
|
|
"MMU: Allocated %zu bytes of context maps for %d contexts\n",
|
2008-12-18 20:13:48 +01:00
|
|
|
2 * CTX_MAP_SIZE + (sizeof(void *) * (last_context + 1)),
|
|
|
|
last_context - first_context + 1);
|
|
|
|
|
2008-12-18 20:13:24 +01:00
|
|
|
/*
|
|
|
|
* Some processors have too few contexts to reserve one for
|
|
|
|
* init_mm, and require using context 0 for a normal task.
|
|
|
|
* Other processors reserve the use of context zero for the kernel.
|
2008-12-18 20:13:48 +01:00
|
|
|
* This code assumes first_context < 32.
|
2008-12-18 20:13:24 +01:00
|
|
|
*/
|
2008-12-18 20:13:48 +01:00
|
|
|
context_map[0] = (1 << first_context) - 1;
|
|
|
|
next_context = first_context;
|
|
|
|
nr_free_contexts = last_context - first_context + 1;
|
2008-12-18 20:13:24 +01:00
|
|
|
}
|
|
|
|
|