RE: [PATCH v2 07/13] x86/irq: Factor out calling ISR from common_interrupt

[Tian, Kevin]

> From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Sent: Saturday, April 6, 2024 6:31 AM
> 
> Prepare for calling external IRQ handlers directly from the posted MSI
> demultiplexing loop. Extract the common code with common interrupt to
> avoid code duplication.
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> ---
>  arch/x86/kernel/irq.c | 23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
> index f39f6147104c..c54de9378943 100644
> --- a/arch/x86/kernel/irq.c
> +++ b/arch/x86/kernel/irq.c
> @@ -242,18 +242,10 @@ static __always_inline void handle_irq(struct
> irq_desc *desc,
>  		__handle_irq(desc, regs);
>  }
> 
> -/*
> - * common_interrupt() handles all normal device IRQ's (the special SMP
> - * cross-CPU interrupts have their own entry points).
> - */
> -DEFINE_IDTENTRY_IRQ(common_interrupt)
> +static __always_inline void call_irq_handler(int vector, struct pt_regs *regs)
>  {
> -	struct pt_regs *old_regs = set_irq_regs(regs);
>  	struct irq_desc *desc;
> 
> -	/* entry code tells RCU that we're not quiescent.  Check it. */
> -	RCU_LOCKDEP_WARN(!rcu_is_watching(), "IRQ failed to wake up
> RCU");
> -
>  	desc = __this_cpu_read(vector_irq[vector]);
>  	if (likely(!IS_ERR_OR_NULL(desc))) {
>  		handle_irq(desc, regs);

the hidden lines has one problem:

	} else {
		apic_eoi();

		if (desc == VECTOR_UNUSED) {
			...

there will be two EOI's for unused vectors, adding the one
in sysvec_posted_msi_notification().