[PATCH v2 3/3] arm64: Allow nVHE impaired CPUs to boot without CONFIG_ARM64_VHE

[Will Deacon]

On Tue, Mar 30, 2021 at 06:39:47PM +0100, Marc Zyngier wrote:
> CPUs stuck in VHE mode need some additional care if the kernel
> is compiled without CONFIG_ARM64_VHE.
> 
> Treat this case as another version of a mismatched boot, and
> prevent KVM from being initialised. The machine will boot in
> some bizarre state, using TPIDR_EL1 instead of TPIDR_EL2, but
> otherwise be functional.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/include/asm/virt.h | 18 +++++++++++++-----
>  arch/arm64/kvm/va_layout.c    |  9 +++++++++
>  2 files changed, 22 insertions(+), 5 deletions(-)

Hmm, I think we definitely need _something_ here, but it's a bit annoying
to put ourselves into this weird state just for the sake of one stupid
machine.

What if we dropped CONFIG_ARM64_VHE and made the VHE code unconditional
instead? Is there a good reason to allow it to be disabled nowadays?

Will