linux-kernel - Re: [PATCH v17 02/10] x86: kdump: make the lower bound of crash kernel reservation consistent

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Date:   Wed, 15 Dec 2021 10:10:34 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Borislav Petkov <bp@...en8.de>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, <x86@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>, <linux-kernel@...r.kernel.org>,
        Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        <kexec@...ts.infradead.org>, 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>
Subject: Re: [PATCH v17 02/10] x86: kdump: make the lower bound of crash
 kernel reservation consistent



On 2021/12/15 3:24, Catalin Marinas wrote:
> On Tue, Dec 14, 2021 at 08:07:58PM +0100, Borislav Petkov wrote:
>> On Fri, Dec 10, 2021 at 02:55:25PM +0800, Zhen Lei wrote:
>>> From: Chen Zhou <chenzhou10@...wei.com>
>>>
>>> The lower bounds of crash kernel reservation and crash kernel low
>>> reservation are different, use the consistent value CRASH_ALIGN.
>>
>> A big WHY is missing here to explain why the lower bound of the
>> allocation range needs to be 16M and why was 0 wrong?
> 
> I asked the same here:
> 
> https://lore.kernel.org/r/20210224143547.GB28965@arm.com
> 
> IIRC Baoquan said that there is a 1MB reserved for x86 anyway in the
> lower part, so that's equivalent in practice to starting from
> CRASH_ALIGN.
> 
> Anyway, I agree the commit log should describe this.

OK, I will add the description.

>