linux-kernel - Re: [PATCH] MIPS: reserve the memblock right after the kernel

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Message-ID: <4a73a75f-a3b2-7ba1-d8a1-a46f5c20e734@loongson.cn>
Date:   Fri, 13 Nov 2020 11:28:36 +0800
From:   Jinyang He <hejinyang@...ngson.cn>
To:     Jiaxun Yang <jiaxun.yang@...goat.com>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexander Sverdlin <alexander.sverdlin@...ia.com>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org, Paul Burton <paulburton@...nel.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] MIPS: reserve the memblock right after the kernel

Hi, Jiaxun,

On 11/13/2020 10:30 AM, Jiaxun Yang wrote:
> Hi all,
>
> 在 2020/11/11 22:52, Serge Semin 写道:
>> Hello Alexander
>>
>> On Tue, Nov 10, 2020 at 11:29:50AM +0100, Alexander Sverdlin wrote:
>> 2) The check_kernel_sections_mem() method can be removed. But it
>> should be done carefully. We at least need to try to find all the
>> platforms, which rely on its functionality.
> It have been more than 10 years since introducing this this check, but
> I believe there must be a reason at the time.
>
> Also currently we have some unmaintained platform and it's impossible
> to test on them for us.
>
> For Cavium's issue, I believe removing the page rounding can help.
> I'd suggest keep this method but remove the rounding part, also
> leave a warning or kernel taint when out of boundary kernel image
> is detected.
>
> Thanks.
>
> - Jiaxun
>
I found the first submission.
Commit: d3ff93380232 (mips: Make sure kernel memory is in iomem)
As I thought, this check is related to kdump. More directly, it is
related to the "mem=" parameter. Kexec-tools provide a "mem=" parameter
to limit the kernel location in kdump. But sometimes the memory may be not
enough and this check gives a way to ensure the capture kernel can
start rightly. Although "mem=" is not in kexec-tools now, I thought
it is also useful if someone use "mem=" to do other things.

Thanks,
Jinyang

>>
>> -Sergey
>>
>>> -- 
>>> Best regards,
>>> Alexander Sverdlin.