linux-kernel - Re: [PATCH RFC] x86/apic: skip cpu slot reservation logic on boot in case of NR

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Message-ID: <YxI+1OjkpFz1mE8L@yury-laptop>
Date:   Fri, 2 Sep 2022 10:35:16 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH RFC] x86/apic: skip cpu slot reservation logic on boot in
 case of NR_CPUS == 1

On Fri, Sep 02, 2022 at 10:14:51AM -0700, Dave Hansen wrote:
> On 9/2/22 09:42, Yury Norov wrote:
> > This is RFC because I'm not sure that this is not a false positive from
> > smatch. If NR_CPUS is 1, and the condition is always true, it's simply
> > optimized out by a compiler, and nothing wrong happens, except maybe a
> > couple of checks on boot.
> 
> I think it's a reasonable warning, but it's also not something we need
> to hack around.  We can surely only land in here with
> boot_cpu_detected==true if NR_CPUS==1, so the rest of the expression is
> moot.
> 
> I don't think it's worth adding the #ifdef.

Thanks Dave. Then I'll add a comment and move my series as-is.

Thanks,
Yury