Re: [PATCH v3 05/17] arm64: Don't enable VHE for the kernel if OVERRIDE_HVHE is set

Catalin Marinas
2023-06-12T19:12:30Z

On Fri, Jun 09, 2023 at 05:21:48PM +0100, Marc Zyngier wrote:
> If the OVERRIDE_HVHE SW override is set (as a precursor of
> the KVM_HVHE capability), do not enable VHE for the kernel
> and drop to EL1 as if VHE was either disabled or unavailable.
>
> Further changes will enable VHE at EL2 only, with the kernel
> still running at EL1.
>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
> arch/arm64/kernel/hyp-stub.S | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
> index 9439240c3fcf..5c71e1019545 100644
> --- a/arch/arm64/kernel/hyp-stub.S
> +++ b/arch/arm64/kernel/hyp-stub.S
> @@ -82,7 +82,15 @@ SYM_CODE_START_LOCAL(__finalise_el2)
> tbnz x1, #0, 1f
>
> // Needs to be VHE capable, obviously
> - check_override id_aa64mmfr1 ID_AA64MMFR1_EL1_VH_SHIFT 2f 1f x1 x2
> + check_override id_aa64mmfr1 ID_AA64MMFR1_EL1_VH_SHIFT 0f 1f x1 x2
> +
> +0: // Check whether we only want the hypervisor to run VHE, not the kernel
> + adr_l x1, arm64_sw_feature_override
> + ldr x2, [x1, FTR_OVR_VAL_OFFSET]
> + ldr x1, [x1, FTR_OVR_MASK_OFFSET]
> + and x2, x2, x1
> + ubfx x2, x2, #ARM64_SW_FEATURE_OVERRIDE_HVHE, #4
> + cbz x2, 2f

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

(I think we are trying too hard to make this look like a hardware
features when a tbz would do ;)).

--
Catalin