Re: [PATCH v2 07/11] x86/irq: Move irq stacks to percpu hot section

[Peter Zijlstra]

On Wed, Feb 26, 2025 at 01:05:26PM -0500, Brian Gerst wrote:

> diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
> index 474af15ae017..2cd2064457b1 100644
> --- a/arch/x86/kernel/irq.c
> +++ b/arch/x86/kernel/irq.c
> @@ -34,6 +34,11 @@ EXPORT_PER_CPU_SYMBOL(irq_stat);
>  DEFINE_PER_CPU_CACHE_HOT(u16, __softirq_pending);
>  EXPORT_PER_CPU_SYMBOL(__softirq_pending);
>  
> +DEFINE_PER_CPU_CACHE_HOT(struct irq_stack *, hardirq_stack_ptr);
> +#ifdef CONFIG_X86_64
> +DEFINE_PER_CPU_CACHE_HOT(bool, hardirq_stack_inuse);
> +#endif
> +
>  atomic_t irq_err_count;
>  
>  /*

Perhaps instead of the above #ifdef,...

> diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
> index dc1049c01f9b..48a27cde9635 100644
> --- a/arch/x86/kernel/irq_32.c
> +++ b/arch/x86/kernel/irq_32.c
> @@ -52,6 +52,8 @@ static inline int check_stack_overflow(void) { return 0; }
>  static inline void print_stack_overflow(void) { }
>  #endif
>  
> +DEFINE_PER_CPU_CACHE_HOT(struct irq_stack *, softirq_stack_ptr);
> +
>  static void call_on_stack(void *func, void *stack)
>  {
>  	asm volatile("xchgl	%%ebx,%%esp	\n"

> diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
> index 56bdeecd8ee0..4834e317e568 100644
> --- a/arch/x86/kernel/irq_64.c
> +++ b/arch/x86/kernel/irq_64.c

stick it in this file, like you already did for the 32bit case?