[U-Boot] [PATCH] ARM: tegra: restrict usable RAM size further

[Simon Glass]

Hi,

On 30 July 2015 at 09:43, Stephen Warren <swarren at wwwdotorg.org> wrote:
>
> On 07/30/2015 05:04 AM, Thierry Reding wrote:
>>
>> On Wed, Jul 29, 2015 at 01:47:58PM -0600, Stephen Warren wrote:
>>>
>>> From: Stephen Warren <swarren at nvidia.com>
>>>
>>> Additionally, ARM64 devices typically run a secure monitor in EL3 and
>>> U-Boot in EL2, and set up some secure RAM carve-outs to contain the EL3
>>> code and data. These carve-outs are located at the top of 32-bit address
>>> space. Restrict U-Boot's RAM usage to well below the location of those
>>> carve-outs. Ideally, we would the secure monitor would inform U-Boot of
>>> exactly which RAM it could use at run-time. However, I'm not sure how to
>>> do that at present (and even if such a mechanism does exist, it would
>>> likely not be generic across all forms of secure monitor).
>>
>>
>> 0xe0000000-0xffffffff is 512 MiB, surely a secure monitor can live with
>> less than that!
>
>
> I'm sure it does. However, it's a nice round number and leaves plenty of space for arbitrary expansion of the secure monitor, secure OS, other security-related carve-outs, (video regions, LP0 resume firmware, etc.) There's still plenty of space left for U-Boot after that.

I'd really hope that these can be in U-Boot's remit. except perhaps
the secure OS. Should we figure out how to build the secure monitor
within the U-Boot environment? Is creating a bootable image going to
become really complicated? Why would video regions and resume firmware
not be set up by U-Boot?

Regards,
Simon