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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date: Thu, 22 Sep 2016 16:03:20 +0100
Message-ID: <CAKv+Gu92SzouihE0cuMNNjrDQgo2-FeNcQBnCXQtyN=OmgsDBg@mail.gmail.com>
To: valerij zaporogeci <vlrzprgts@gmail.com>
Cc: edk2-devel <edk2-devel@lists.01.org>
Subject: Re: flat mapping vs identity mapping on ARM
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On 22 September 2016 at 15:30, valerij zaporogeci <vlrzprgts@gmail.com> wrote:
> In the ARM architecture, there is such a thing - "flat mapping", where
> MMU stage 1 is disabled and the mapping done is 1:1 and attributes set
> to the predefined values.

What do you mean by 'attributes set to the predefined values' ?

> Did I understand right, that this is NOT what UEFI means by "identity
> mapping" with MMU enabled? And in the latter case there is need to
> create all those page tables and stuff, setting 1:1 mapping between VA
> and PA? If so, why to do that? Why "flat mapping" isn't what UEFI
> would love to see as its mapping regime?

On ARM, you need to enable the MMU in order to enable the Dcache.