linux-kernel - Re: [PATCH v3 1/2] arm64: topology: move store_cpu

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Message-ID: <Ysw4voXuz+tcSKhf@kroah.com>
Date:   Mon, 11 Jul 2022 16:50:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Conor Dooley <mail@...chuod.ie>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Daire McNamara <daire.mcnamara@...rochip.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Niklas Cassel <niklas.cassel@....com>,
        Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Zong Li <zong.li@...ive.com>,
        Emil Renner Berthing <kernel@...il.dk>,
        Jonas Hahnfeld <hahnjo@...njo.de>, Guo Ren <guoren@...nel.org>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Philipp Tomsich <philipp.tomsich@...ll.eu>,
        Rob Herring <robh@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Brice Goglin <Brice.Goglin@...ia.fr>
Subject: Re: [PATCH v3 1/2] arm64: topology: move store_cpu_topology() to
 shared code

On Mon, Jul 11, 2022 at 03:35:42PM +0100, Sudeep Holla wrote:
> On Sat, Jul 09, 2022 at 04:23:54PM +0100, Conor Dooley wrote:
> > From: Conor Dooley <conor.dooley@...rochip.com>
> > 
> > arm64's method of defining a default cpu topology requires only minimal
> > changes to apply to RISC-V also. The current arm64 implementation exits
> > early in a uniprocessor configuration by reading MPIDR & claiming that
> > uniprocessor can rely on the default values.
> > 
> > This is appears to be a hangover from prior to '3102bc0e6ac7 ("arm64:
> > topology: Stop using MPIDR for topology information")', because the
> > current code just assigns default values for multiprocessor systems.
> > 
> > With the MPIDR references removed, store_cpu_topolgy() can be moved to
> > the common arch_topology code.
> >
> 
> Looks good. FWIW,
> 
> Reviewed-by: Sudeep Holla <sudeep.holla@....com>
> 
> > CC: stable@...r.kernel.org
> 
> However, while I understand the reason why this is needed in stable trees
> for RISC-V, I am not sure if we want this for stable tree at-least on arm64.
> I leave that part to Greg and Will.

Why would it be good for one arch but bad for another?