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From: "Tian, Kevin" <kevin.tian@intel.com>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>, LKML
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Subject: RE: [PATCH v2 07/13] x86/irq: Factor out calling ISR from
 common_interrupt
Thread-Topic: [PATCH v2 07/13] x86/irq: Factor out calling ISR from
 common_interrupt
Thread-Index: AQHah6hf0+1860aOe0i/wzWWSuIGmbFkZOjw
Date: Fri, 12 Apr 2024 09:21:45 +0000
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References: <20240405223110.1609888-1-jacob.jun.pan@linux.intel.com>
 <20240405223110.1609888-8-jacob.jun.pan@linux.intel.com>
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> From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Sent: Saturday, April 6, 2024 6:31 AM
>=20
> Prepare for calling external IRQ handlers directly from the posted MSI
> demultiplexing loop. Extract the common code with common interrupt to
> avoid code duplication.
>=20
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
>  arch/x86/kernel/irq.c | 23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)
>=20
> 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);
>  }
>=20
> -/*
> - * 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 =3D set_irq_regs(regs);
>  	struct irq_desc *desc;
>=20
> -	/* entry code tells RCU that we're not quiescent.  Check it. */
> -	RCU_LOCKDEP_WARN(!rcu_is_watching(), "IRQ failed to wake up
> RCU");
> -
>  	desc =3D __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 =3D=3D VECTOR_UNUSED) {
			...

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