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

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Message-ID: <13fff200-660a-27b8-6507-82124eee51c5@nokia.com>
Date:   Fri, 13 Nov 2020 14:09:09 +0100
From:   Alexander Sverdlin <alexander.sverdlin@...ia.com>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        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

Hello Serge, Thomas,

On 13/11/2020 10:17, Alexander Sverdlin wrote:
>> So IMHO what could be the best conclusion in the framework of this patch:
>> 1) As Thomas said any platform-specific reservation should be done in the
>> platform-specific code. That means if octeon needs some memory behind
>> the kernel being reserved, then it should be done for example in
>> prom_init().
>> 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.
> Thanks for looking into this! I agree with your analysis, I'll try to rework,
> removing check_kernel_sections_mem().

but now, after grepping inside arch/mips, I found that only Octeon does memblock_add()
of the area between _text and _and explicitly.

Therefore, maybe many other platforms indeed rely on check_kernel_sections_mem()?
Maybe the proper way would be really to remote the PFN_UP()/PFN_DOWN() from
check_kernel_sections_mem(), which is not necessary after commit b10d6bca8720
("arch, drivers: replace for_each_membock() with for_each_mem_range()")
which fixed the resource_init()?

As completely unrelated optimization I can remove the same memblock_add() of the
kernel sections from the Octeon platform code. 

-- 
Best regards,
Alexander Sverdlin.