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/*
* linux/arch/arm/mm/context.c
*
* Copyright (C) 2002-2003 Deep Blue Solutions Ltd, all rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/percpu.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
static DEFINE_SPINLOCK(cpu_asid_lock);
unsigned int cpu_last_asid = ASID_FIRST_VERSION;
#ifdef CONFIG_SMP
DEFINE_PER_CPU(struct mm_struct *, current_mm);
#endif
/*
* We fork()ed a process, and we need a new context for the child
* to run in. We reserve version 0 for initial tasks so we will
* always allocate an ASID. The ASID 0 is reserved for the TTBR
* register changing sequence.
*/
void __init_new_context(struct task_struct *tsk, struct mm_struct *mm)
{
mm->context.id = 0;
spin_lock_init(&mm->context.id_lock);
}
static void flush_context(void)
{
/* set the reserved ASID before flushing the TLB */
asm("mcr p15, 0, %0, c13, c0, 1\n" : : "r" (0));
isb();
local_flush_tlb_all();
if (icache_is_vivt_asid_tagged()) {
__flush_icache_all();
dsb();
}
}
#ifdef CONFIG_SMP
static void set_mm_context(struct mm_struct *mm, unsigned int asid)
{
unsigned long flags;
/*
* Locking needed for multi-threaded applications where the
* same mm->context.id could be set from different CPUs during
* the broadcast. This function is also called via IPI so the
* mm->context.id_lock has to be IRQ-safe.
*/
spin_lock_irqsave(&mm->context.id_lock, flags);
if (likely((mm->context.id ^ cpu_last_asid) >> ASID_BITS)) {
/*
* Old version of ASID found. Set the new one and
* reset mm_cpumask(mm).
*/
mm->context.id = asid;
cpumask_clear(mm_cpumask(mm));
}
spin_unlock_irqrestore(&mm->context.id_lock, flags);
/*
* Set the mm_cpumask(mm) bit for the current CPU.
*/
cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
}
/*
* Reset the ASID on the current CPU. This function call is broadcast
* from the CPU handling the ASID rollover and holding cpu_asid_lock.
*/
static void reset_context(void *info)
{
unsigned int asid;
unsigned int cpu = smp_processor_id();
struct mm_struct *mm = per_cpu(current_mm, cpu);
/*
* Check if a current_mm was set on this CPU as it might still
* be in the early booting stages and using the reserved ASID.
*/
if (!mm)
return;
smp_rmb();
asid = cpu_last_asid + cpu + 1;
flush_context();
set_mm_context(mm, asid);
/* set the new ASID */
asm("mcr p15, 0, %0, c13, c0, 1\n" : : "r" (mm->context.id));
isb();
}
#else
static inline void set_mm_context(struct mm_struct *mm, unsigned int asid)
{
mm->context.id = asid;
cpumask_copy(mm_cpumask(mm), cpumask_of(smp_processor_id()));
}
#endif
void __new_context(struct mm_struct *mm)
{
unsigned int asid;
spin_lock(&cpu_asid_lock);
#ifdef CONFIG_SMP
/*
* Check the ASID again, in case the change was broadcast from
* another CPU before we acquired the lock.
*/
if (unlikely(((mm->context.id ^ cpu_last_asid) >> ASID_BITS) == 0)) {
cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
spin_unlock(&cpu_asid_lock);
return;
}
#endif
/*
* At this point, it is guaranteed that the current mm (with
* an old ASID) isn't active on any other CPU since the ASIDs
* are changed simultaneously via IPI.
*/
asid = ++cpu_last_asid;
if (asid == 0)
asid = cpu_last_asid = ASID_FIRST_VERSION;
/*
* If we've used up all our ASIDs, we need
* to start a new version and flush the TLB.
*/
if (unlikely((asid & ~ASID_MASK) == 0)) {
asid = cpu_last_asid + smp_processor_id() + 1;
flush_context();
#ifdef CONFIG_SMP
smp_wmb();
smp_call_function(reset_context, NULL, 1);
#endif
cpu_last_asid += NR_CPUS;
}
set_mm_context(mm, asid);
spin_unlock(&cpu_asid_lock);
}
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