Commit 71586276 authored by Will Deacon's avatar Will Deacon Committed by Catalin Marinas
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arm64: percpu: implement optimised pcpu access using tpidr_el1

This patch implements optimised percpu variable accesses using the
el1 r/w thread register (tpidr_el1) along the same lines as arch/arm/.
Signed-off-by: default avatarWill Deacon <>
Signed-off-by: default avatarCatalin Marinas <>
parent 66aa8d6a
......@@ -26,7 +26,6 @@ generic-y += mman.h
generic-y += msgbuf.h
generic-y += mutex.h
generic-y += pci.h
generic-y += percpu.h
generic-y += poll.h
generic-y += posix_types.h
generic-y += resource.h
* Copyright (C) 2013 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
* 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 <>.
#ifndef __ASM_PERCPU_H
#define __ASM_PERCPU_H
static inline void set_my_cpu_offset(unsigned long off)
asm volatile("msr tpidr_el1, %0" :: "r" (off) : "memory");
static inline unsigned long __my_cpu_offset(void)
unsigned long off;
register unsigned long *sp asm ("sp");
* We want to allow caching the value, so avoid using volatile and
* instead use a fake stack read to hazard against barrier().
asm("mrs %0, tpidr_el1" : "=r" (off) : "Q" (*sp));
return off;
#define __my_cpu_offset __my_cpu_offset()
#include <asm-generic/percpu.h>
#endif /* __ASM_PERCPU_H */
......@@ -108,6 +108,16 @@ void __init early_print(const char *str, ...)
printk("%s", buf);
void __init smp_setup_processor_id(void)
* clear __my_cpu_offset on boot CPU to avoid hang caused by
* using percpu variable early, for example, lockdep will
* access percpu variable inside lock_release
bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
return phys_id == cpu_logical_map(cpu);
......@@ -122,8 +122,6 @@ asmlinkage void secondary_start_kernel(void)
struct mm_struct *mm = &init_mm;
unsigned int cpu = smp_processor_id();
printk("CPU%u: Booted secondary processor\n", cpu);
* All kernel threads share the same mm context; grab a
* reference and switch to it.
......@@ -132,6 +130,9 @@ asmlinkage void secondary_start_kernel(void)
current->active_mm = mm;
cpumask_set_cpu(cpu, mm_cpumask(mm));
printk("CPU%u: Booted secondary processor\n", cpu);
* TTBR0 is only used for the identity mapping at this stage. Make it
* point to zero page to avoid speculatively fetching new entries.
......@@ -271,6 +272,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
void __init smp_prepare_boot_cpu(void)
static void (*smp_cross_call)(const struct cpumask *, unsigned int);
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