Subject: Re: [PATCH v17 02/10] x86: kdump: make the lower bound of crash
 kernel reservation consistent
To:     Catalin Marinas <catalin.marinas@arm.com>,
        Borislav Petkov <bp@alien8.de>
CC:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, <x86@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>, <linux-kernel@vger.kernel.org>,
        Dave Young <dyoung@redhat.com>, Baoquan He <bhe@redhat.com>,
        Vivek Goyal <vgoyal@redhat.com>,
        Eric Biederman <ebiederm@xmission.com>,
        <kexec@lists.infradead.org>, 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>
References: <20211210065533.2023-1-thunder.leizhen@huawei.com>
 <20211210065533.2023-3-thunder.leizhen@huawei.com> <YbjrjpehprvoRXbV@zn.tnic>
 <YbjvXl51hc6GZa71@arm.com>
From:   "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
Message-ID: <07e41d65-bc3a-49c4-c041-752f1765f37a@huawei.com>
Date:   Wed, 15 Dec 2021 10:10:34 +0800
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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@huawei.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.

>