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Date:   Sat, 3 Oct 2020 22:07:05 +0100 (BST)
From:   "Maciej W. Rozycki" <macro@linux-mips.org>
To:     Baoquan He <bhe@redhat.com>
cc:     Huacai Chen <chenhc@lemote.com>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Eric Biederman <ebiederm@xmission.com>,
        Dave Young <dyoung@redhat.com>,
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        "open list:MIPS" <linux-mips@vger.kernel.org>,
        kexec@lists.infradead.org, Fuxin Zhang <zhangfx@lemote.com>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>
Subject: Re: [PATCH 1/3] MIPS: Crash kernel should be able to see old
 memories
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On Wed, 23 Sep 2020, Baoquan He wrote:

> > > And we don't have mem=X@Y, only mem=nn[KMG].
> > The relocatable kernel of MIPS is still unusable now, so MIPS should
> > use mem=X@Y, and the crash kernel is always different from normal
> > kernel.
> 
> Interesting. Seems MIPS does support mem=X@Y, even though the document
> of 'mem=' says it's used to specify amount of memory, but not memory
> region. Anyway, leave this to mips reviewers, thanks for replying.
> 
> ~~~~~~~~~~~~~~~~~~~
>         mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
>                         Amount of memory to be used in cases as follows:

 Yep, I implemented it for the DECstation back in 2000:

commit 97b7ae4257ef7ba8ed9b7944a4f56a49af3e8abb
Author: Ralf Baechle <ralf@linux-mips.org>
Date:   Mon Dec 11 16:41:05 2000 +0000

    Memmap fixes from Maciej.

(from the LMO repo) in line with the x86 syntax.  I don't know why it 
hasn't ever been documented in "Kernel Parameters" (for any port), but I'm 
fairly sure it has been somewhere.

 FWIW,

  Maciej