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Date: Fri, 1 Aug 2014 19:04:11 +0200
From: Robert Richter <rric@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Ganapatrao Kulkarni <gpkulkarni@gmail.com>,
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Subject: Re: [PATCH 2/5] arm64, thunder: Add initial dts for Cavium Thunder
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Mark,

On 31.07.14 12:33:01, Mark Rutland wrote:
> On Thu, Jul 31, 2014 at 12:12:33PM +0100, Ganapatrao Kulkarni wrote:
> >    We mark RAM used by ATF as secure-RAM, however we don't support
> >    secure/non-secure address aliasing.
> >    i.e, a DRAM address that can be referenced from both a secure PA and a
> >    non-secure PA is not allowed.
>
> What exactly do you mean by "not allowed"?

It actually means "not possible" since secure and non-secure memory is
kept in separate address ranges.

> If Linux maps that memory, what happens?
>
> What if Linux tried to read or write to it?
>
> If Linux should not map that memory, it should not be described in the
> memory map to begin with.

Linux never will see secure-RAM. Firmware must be sure to report the
correct non-secure memory ranges to the OS (e.g. unsecure mem size =
total size - secure mem size).

-Robert