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

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Message-ID: <8722acbe-c668-5b05-c030-565f8c42068c@intel.com>
Date:   Fri, 2 Sep 2022 10:14:51 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Yury Norov <yury.norov@...il.com>,
        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
Cc:     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 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.