Re: [PATCH v2 3/3] KVM: arm64: Make ID_AA64MMFR1_EL1.VH writable from userspace

[Oliver Upton]

Hi Jinqian,

On Tue, Sep 09, 2025 at 11:44:15AM +0800, Jinqian Yang wrote:
> Allow userspace to downgrade VH in ID_AA64MMFR1_EL1. Userspace can
> only change this value from high to low.

I'm afraid we can't allow this. When we expose FEAT_VHE to the VM,
HCR_EL2.E2H is RES1. Meaning, vEL2 is unconditionally in a VHE
context.

I would be OK with a clarifying comment documenting why the field is
non-writable.

Thanks,
Oliver