linux-kernel - Re: [PATCH] x86/idt: Simplify the idt_setup_apic_and_irq

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Message-ID: <alpine.DEB.2.21.1805221617080.1711@nanos.tec.linutronix.de>
Date:   Tue, 22 May 2018 16:17:37 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dou Liyang <douly.fnst@...fujitsu.com>
cc:     x86@...nel.org, linux-kernel@...r.kernel.org, mingo@...hat.com,
        hpa@...or.com
Subject: Re: [PATCH] x86/idt: Simplify the idt_setup_apic_and_irq_gates()

On Tue, 22 May 2018, Dou Liyang wrote:

> Hi Thomas,
> 
> At 05/19/2018 08:32 PM, Thomas Gleixner wrote:
> > On Thu, 26 Apr 2018, Dou Liyang wrote:
> > 
> > > The vectors between FIRST_SYSTEM_VECTOR and NR_VECTORS are special IRQ
> > > vectors used by the SMP architecture. But, if X86_LOCAL_APIC=n, it will
> > > not be used, and the FIRST_SYSTEM_VECTOR is equal to NR_VECTORS.
> > 
> > Correct, but that function has nothing to do with FIRST_SYSTEM_VECTOR.
> > 
> 
> Oops, sorry, when I reread, my changelog even made me misunderstand.
> the patch hided it.
> 
>     void __init idt_setup_apic_and_irq_gates(void)
>     ...
>         for_each_clear_bit_from(i, system_vectors, FIRST_SYSTEM_VECTOR)
>                                                    ^^^^^^^^^^^^^^^^^^^
>     ...
>         for_each_clear_bit_from(i, system_vectors, NR_VECTORS)
> 
> What I want to say is:
> 
>   In the APIC=n system, the FIRST_SYSTEM_VECTOR is equal to
>   NR_VECTORS, So all entries has been set by
> 
>     for_each_clear_bit_from(i, system_vectors, FIRST_SYSTEM_VECTOR)
>        ...
> 
>   the following setup code for APIC=n is redundant. Just setup gates for
>   APIC=y.
> 
> If it is OK, I will send v2.

Right you are. I got confused ....