Re: [PATCH 0/2] arm64: booting.rst: Clarify EL2 and cover v8-R64

Will Deacon
2022-02-15T23:18:43Z

On Fri, 7 Jan 2022 16:00:54 +0000, Andre Przywara wrote:
> clarify the wording of the ARM64 boot protocol requirements, to both
> cater for the introduction of secure EL2 in Armv8.4, but also for the
> addition of the Armv8-R64 architecture branch.
> There is an ARM ARM supplement for v8-R64[1], and also a free model[2].
>
> On top of those clarifications, there are at least two other issues to
> consider for v8-R64 on Linux, I wonder if those should be documented
> somewhere, although I doubt that booting.rst is the right place:
> - Linux clears the NS/NSTable bit in the PTEs. In non-secure world those
> bits are ignored, but when in secure world this means "secure PA".
> That luckily matches the design here (secure-only), but we should avoid
> re-purposing those bits in the future (which would be technically
> possible when running only non-secure).
> - The GIC needs to be implemented using a "single Security state" for
> the Linux GIC driver to work. The model mentioned above defaults to
> a security aware GIC, so needs to be told off using the command line.
> I wonder if this is should be explicitly mentioned somewhere, to avoid
> disappointment by implementors later.
>
> [...]

Applied first patch to arm64 (for-next/docs), thanks!

[1/2] arm64: booting.rst: Clarify on requiring non-secure EL2
https://git.kernel.org/arm64/c/b8ac4ee08d48

Cheers,
--
Will