linux-kernel - Re: [PATCH v3 2/2] x86: Fix /proc/cpuinfo cpumask warning

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Message-ID: <20221031080604.6xei6c4e3ckhsvmy@kamzik>
Date:   Mon, 31 Oct 2022 09:06:04 +0100
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Yury Norov <yury.norov@...il.com>, x86@...nel.org,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Stafford Horne <shorne@...il.com>,
        openrisc@...ts.librecores.org,
        Michael Ellerman <mpe@...erman.id.au>,
        "open list:LINUX FOR POWERPC PA SEMI PWRFICIENT" 
        <linuxppc-dev@...ts.ozlabs.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH v3 2/2] x86: Fix /proc/cpuinfo cpumask warning

On Fri, Oct 28, 2022 at 06:06:41PM +0200, Borislav Petkov wrote:
> On Fri, Oct 28, 2022 at 10:13:28AM -0500, Yury Norov wrote:
> > Because it's related to bitmap API usage and has been revealed after
> > some work in bitmaps.
> 
> So first of all, that "fix" needs to explain what exactly it is fixing.
> Not "it fixes this and that warning" but why the input arg to
> cpumask_next() cannot be nr_cpu_ids because... yadda yadda...

Hi Boris,

I didn't realize you were still looking for improvements to the commit
message for this patch. I could add something like,

 The valid cpumask range is [0, nr_cpu_ids) and cpumask_next() always
 returns a CPU ID greater than its input, which results in its input
 range being [-1, nr_cpu_ids - 1). Ensure showing CPU info avoids
 triggering error conditions in cpumask_next() by stopping its loop
 over CPUs when its input would be invalid.

Thanks,
drew

> 
> > And because nobody else cares.
> 
> Why do you assume that?
> 
> > If you're willing to move it yourself please go ahead.
> 
> If it fixes a real issue, we are taking it. And pls note that x86
> patches go through the tip tree.
> 
> Thx.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette