context.c
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/*
* Based on arch/arm/mm/context.c
*
* Copyright (C) 2002-2003 Deep Blue Solutions Ltd, all rights reserved.
* Copyright (C) 2012 ARM Ltd.
*
* 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.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#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>
#include <asm/cachetype.h>
#define asid_bits(reg) \
(((read_cpuid(ID_AA64MMFR0_EL1) & 0xf0) >> 2) + 8)
#define ASID_FIRST_VERSION (1 << MAX_ASID_BITS)
static DEFINE_RAW_SPINLOCK(cpu_asid_lock);
unsigned int cpu_last_asid = ASID_FIRST_VERSION;
/*
* We fork()ed a process, and we need a new context for the child to run in.
*/
void __init_new_context(struct task_struct *tsk, struct mm_struct *mm)
{
mm->context.id = 0;
raw_spin_lock_init(&mm->context.id_lock);
}
static void flush_context(void)
{
/* set the reserved TTBR0 before flushing the TLB */
cpu_set_reserved_ttbr0();
flush_tlb_all();
if (icache_is_aivivt())
__flush_icache_all();
}
#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.
*/
raw_spin_lock_irqsave(&mm->context.id_lock, flags);
if (likely((mm->context.id ^ cpu_last_asid) >> MAX_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));
}
raw_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 = current->active_mm;
smp_rmb();
asid = cpu_last_asid + cpu;
flush_context();
set_mm_context(mm, asid);
/* set the new ASID */
cpu_switch_mm(mm->pgd, mm);
}
#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;
unsigned int bits = asid_bits();
raw_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) >> MAX_ASID_BITS)) {
cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
raw_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 we've used up all our ASIDs, we need to start a new version and
* flush the TLB.
*/
if (unlikely((asid & ((1 << bits) - 1)) == 0)) {
/* increment the ASID version */
cpu_last_asid += (1 << MAX_ASID_BITS) - (1 << bits);
if (cpu_last_asid == 0)
cpu_last_asid = ASID_FIRST_VERSION;
asid = cpu_last_asid + smp_processor_id();
flush_context();
#ifdef CONFIG_SMP
smp_wmb();
smp_call_function(reset_context, NULL, 1);
#endif
cpu_last_asid += NR_CPUS - 1;
}
set_mm_context(mm, asid);
raw_spin_unlock(&cpu_asid_lock);
}