linux-kernel - Re: [PATCH v4 1/4] MIPS: Refactor early_parse

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Message-ID: <20220304153517.GA28487@alpha.franken.de>
Date:   Fri, 4 Mar 2022 16:35:17 +0100
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc:     Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Xuefeng Li <lixuefeng@...ngson.cn>, linux-mips@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/4] MIPS: Refactor early_parse_mem() to fix mem=
 parameter

On Fri, Mar 04, 2022 at 04:10:52PM +0100, Thomas Bogendoerfer wrote:
> On Tue, Mar 01, 2022 at 12:28:58PM +0800, Tiezhu Yang wrote:
> > According to Documentation/admin-guide/kernel-parameters.txt,
> > the kernel command-line parameter mem= means "Force usage of
> > a specific amount of memory", but when add "mem=3G" to the
> > command-line, kernel boot hangs in sparse_init().
> > 
> > This commit is similar with the implementation of the other
> > archs such as arm64, powerpc and riscv, refactor the function
> > early_parse_mem() and then use memblock_enforce_memory_limit()
> > to limit the memory size.
> > 
> > With this patch, when add "mem=3G" to the command-line, the
> > kernel boots successfully, we can see the following messages:
> 
> unfortunately this patch would break platforms without memory detection,
> which simply use mem=32M for memory configuration. Not sure how many
> rely on this mechanism. If we can make sure nobody uses it, I'm fine
> with your patch.

maybe we could add a CONFIG option, which will be selected by
platforms, which don't need/want this usermem thing.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]