linux-kernel - Re: [PATCH v19 02/13] x86/setup: Use parse_crashkernel_high

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Message-ID: <Ycw8n2BvJzH9wJKG@dhcp-128-65.nay.redhat.com>
Date:   Wed, 29 Dec 2021 18:46:55 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Baoquan He <bhe@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        kexec@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        linux-doc@...r.kernel.org, Randy Dunlap <rdunlap@...radead.org>,
        Feng Zhou <zhoufeng.zf@...edance.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Chen Zhou <dingguo.cz@...group.com>,
        John Donnelly <John.p.donnelly@...cle.com>
Subject: Re: [PATCH v19 02/13] x86/setup: Use parse_crashkernel_high_low() to
 simplify code

On 12/29/21 at 11:03am, Borislav Petkov wrote:
> On Wed, Dec 29, 2021 at 03:27:48PM +0800, Dave Young wrote:
> > So I think you can unify the parse_crashkernel* in x86 first with just
> > one function.  And leave the further improvements to later work. But
> > let's see how Boris think about this.
> 
> Well, I think this all unnecessary work. Why?
> 
> If the goal is to support crashkernel...high,low on arm64, then you
> should simply *copy* the functionality on arm64 and be done with it.
> 
> Unification is done by looking at code which is duplicated across
> architectures and which has been untouched for a while now, i.e., no
> new or arch-specific changes are going to it so a unification can be
> as simple as trivially switching the architectures to call a generic
> function.
> 
> What this does is carve out the "generic" parts and then try not to
> break existing usage.
> 
> Which is a total waste of energy and resources. And it is casting that
> functionality in stone so that when x86 wants to change something there,
> it should do it in a way not to break arm64. And I fail to see the
> advantage of all that. Code sharing ain't it.
> 
> So what it should do is simply copy the necessary code to arm64.
> Unifications can always be done later, when the dust settles.

I think I agree with you about the better way is to doing some
improvements so that arches can logically doing things better.  I can
leave with the way I suggested although it is not the best.  But I think
Leizhen needs a clear direction about how to do it. It is very clear
now.  See how he will handle this. 

> 
> IMNSVHO.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette
>