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    Subject[patch V3 29/32] x86/irq/64: Init hardirq_stack_ptr during CPU hotplug
    Preparatory change for distangling the irq stack union as a prerequisite
    for irq stacks with guard pages.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    arch/x86/include/asm/irq.h | 4 ----
    arch/x86/kernel/cpu/common.c | 4 +---
    arch/x86/kernel/irq_64.c | 15 +++++++++++++++
    3 files changed, 16 insertions(+), 7 deletions(-)

    --- a/arch/x86/include/asm/irq.h
    +++ b/arch/x86/include/asm/irq.h
    @@ -16,11 +16,7 @@ static inline int irq_canonicalize(int i
    return ((irq == 2) ? 9 : irq);
    }

    -#ifdef CONFIG_X86_32
    extern int irq_init_percpu_irqstack(unsigned int cpu);
    -#else
    -static inline int irq_init_percpu_irqstack(unsigned int cpu) { return 0; }
    -#endif

    #define __ARCH_HAS_DO_SOFTIRQ

    --- a/arch/x86/kernel/cpu/common.c
    +++ b/arch/x86/kernel/cpu/common.c
    @@ -1510,9 +1510,7 @@ DEFINE_PER_CPU(struct task_struct *, cur
    &init_task;
    EXPORT_PER_CPU_SYMBOL(current_task);

    -DEFINE_PER_CPU(char *, hardirq_stack_ptr) =
    - init_per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE;
    -
    +DEFINE_PER_CPU(char *, hardirq_stack_ptr);
    DEFINE_PER_CPU(unsigned int, irq_count) __visible = -1;

    DEFINE_PER_CPU(int, __preempt_count) = INIT_PREEMPT_COUNT;
    --- a/arch/x86/kernel/irq_64.c
    +++ b/arch/x86/kernel/irq_64.c
    @@ -87,3 +87,18 @@ bool handle_irq(struct irq_desc *desc, s
    generic_handle_irq_desc(desc);
    return true;
    }
    +
    +static int map_irq_stack(unsigned int cpu)
    +{
    + void *va = per_cpu_ptr(irq_stack_union.irq_stack, cpu);
    +
    + per_cpu(hardirq_stack_ptr, cpu) = va + IRQ_STACK_SIZE;
    + return 0;
    +}
    +
    +int irq_init_percpu_irqstack(unsigned int cpu)
    +{
    + if (per_cpu(hardirq_stack_ptr, cpu))
    + return 0;
    + return map_irq_stack(cpu);
    +}

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