[PATCH v2 2/3] efi: arm64: Wire up BTI annotation in memory attributes table

[Ard Biesheuvel]

On Mon, 20 Feb 2023 at 16:53, Mark Brown <broonie at kernel.org> wrote:
>
> On Wed, Feb 08, 2023 at 03:36:40PM +0100, Ard Biesheuvel wrote:
>
> > OTOH, what is the penalty for setting the GP attribute and using the
> > translation table on a core that does not implement BTI?
>
> The concern with doing that for Linux was what would happen if someone
> implemented a system with mixed BTI/no BTI support and then a task got
> preempted and moved between the two, you might end up with PSTATE.BTYPE
> incorrectly set and trigger a spurious fault.  That shouldn't be an
> issue for EFI runtime services.

Right, I hadn't figured that. But as you say, this shouldn't affect
EFI runtime services, as they are non-preemptible and therefore
non-migratable.