linux-kernel - Re: [PATCH v3 03/23] arm64: Make cpu_logical

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Date:   Thu, 26 Nov 2020 17:28:38 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     David Brazdil <dbrazdil@...gle.com>
Cc:     kvmarm@...ts.cs.columbia.edu, Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kernel-team@...roid.com
Subject: Re: [PATCH v3 03/23] arm64: Make cpu_logical_map() take unsigned int

On Thu, Nov 26, 2020 at 03:54:01PM +0000, David Brazdil wrote:
> CPU index should never be negative. Change the signature of
> (set_)cpu_logical_map to take an unsigned int.
> 
> Signed-off-by: David Brazdil <dbrazdil@...gle.com>

Is there a function problem here, or is this just cleanup from
inspection?

Core code including the cpuhp_*() callbacks uses an int, so if there's a
strong justification to change this, it suggests there's some treewide
cleanup that should be done.

I don't have strong feelings on the matter, but I'd like to understand
the rationale.

Thanks,
Mark.

> ---
>  arch/arm64/include/asm/smp.h | 4 ++--
>  arch/arm64/kernel/setup.c    | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
> index 2e7f529ec5a6..bcb01ca15325 100644
> --- a/arch/arm64/include/asm/smp.h
> +++ b/arch/arm64/include/asm/smp.h
> @@ -46,9 +46,9 @@ DECLARE_PER_CPU_READ_MOSTLY(int, cpu_number);
>   * Logical CPU mapping.
>   */
>  extern u64 __cpu_logical_map[NR_CPUS];
> -extern u64 cpu_logical_map(int cpu);
> +extern u64 cpu_logical_map(unsigned int cpu);
>  
> -static inline void set_cpu_logical_map(int cpu, u64 hwid)
> +static inline void set_cpu_logical_map(unsigned int cpu, u64 hwid)
>  {
>  	__cpu_logical_map[cpu] = hwid;
>  }
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 133257ffd859..2f2973bc67c7 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -276,7 +276,7 @@ arch_initcall(reserve_memblock_reserved_regions);
>  
>  u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };
>  
> -u64 cpu_logical_map(int cpu)
> +u64 cpu_logical_map(unsigned int cpu)
>  {
>  	return __cpu_logical_map[cpu];
>  }
> -- 
> 2.29.2.454.gaff20da3a2-goog
>