Re: [PATCH v19 02/13] x86/setup: Use parse_crashkernel_high_low() to simplify code

From: Borislav Petkov <bp@alien8.de>
To: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
Cc: Dave Young <dyoung@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
	linux-kernel@vger.kernel.org, Baoquan He <bhe@redhat.com>,
	Vivek Goyal <vgoyal@redhat.com>,
	Eric Biederman <ebiederm@xmission.com>,
	kexec@lists.infradead.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	devicetree@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
	linux-doc@vger.kernel.org, Randy Dunlap <rdunlap@infradead.org>,
	Feng Zhou <zhoufeng.zf@bytedance.com>,
	Kefeng Wang <wangkefeng.wang@huawei.com>,
	Chen Zhou <dingguo.cz@antgroup.com>,
	John Donnelly <John.p.donnelly@oracle.com>
Subject: Re: [PATCH v19 02/13] x86/setup: Use parse_crashkernel_high_low() to simplify code
Date: Wed, 29 Dec 2021 17:51:29 +0100	[thread overview]
Message-ID: <YcySEdyhXysDSKn/@zn.tnic> (raw)
In-Reply-To: <21736ba2-883d-1037-dbe8-299e40f7ad13@huawei.com>

On Wed, Dec 29, 2021 at 11:04:21PM +0800, Leizhen (ThunderTown) wrote:
> Chen Zhou and I tried to share the code because of a suggestion. After so many
> attempts, it doesn't seem to fit to make generic. Or maybe I haven't figured
> out a good solution yet.

Well, you learned a very important lesson and the many attempts are not
in vain: code sharing does not make sense in every case.

> I will put the patches that make arm64 support crashkernel...high,low to
> the front, then the parse_crashkernel() unification patches. Even if the
> second half of the patches is not ready for v5.18, the first half of the
> patches is ready.

I think you should concentrate on the arm64 side which is, AFAICT, what
you're trying to achieve.

The "parse_crashkernel() unification" needs more thought because, as I
said already, that doesn't make a whole lot of sense to me.

If you want to enforce the fact that "low" makes sense only when "high"
is supplied, parse_crashkernel_high_low() is not the right thing to do.
You need to have a *single* function which does all the parsing where
you can decide what to do: "if high, parse low", "if no high supplied,
ignore low" and so on.

And if those are supported on certain architectures only, you can do
ifdeffery...

But I think I already stated that I don't like such unifications which
introduce unnecessary dependencies between architectures. Therefore, I
won't accept them into x86 unless there's a strong compelling reason.
Which I don't see ATM.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

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