Re: [PATCH v4 2/8] KVM: arm64: Make vcpu_{read,write}_sys_reg available to HYP code

[Oliver Upton <oupton@kernel.org>]

Hi Fuad,

On Mon, Jul 06, 2026 at 10:59:21AM +0100, Fuad Tabba wrote:
> The vcpu_{read,write}_sys_reg() accessors are host-only, so helpers
> built on them such as kvm_vcpu_set_be()/kvm_vcpu_is_be() cannot be
> shared with hyp code. exception.c already wraps them in
> __vcpu_{read,write}_sys_reg(), which pick the host- or hyp-side accessor
> via has_vhe() and so are valid in any context.
> 
> Move those wrappers to kvm_emulate.h as kvm_vcpu_{read,write}_sys_reg()
> and switch the callers over, so a follow-up series can share that
> emulation code at EL2.
> 
> No functional change intended.
> 
> Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
> Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
> ---
>  arch/arm64/include/asm/kvm_emulate.h | 22 +++++++++++++++---
>  arch/arm64/kvm/hyp/exception.c       | 34 ++++++++--------------------
>  2 files changed, 28 insertions(+), 28 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index 5bf3d7e1d92c7..80b30fead3d16 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -506,6 +506,22 @@ static inline unsigned long kvm_vcpu_get_mpidr_aff(struct kvm_vcpu *vcpu)
>  	return __vcpu_sys_reg(vcpu, MPIDR_EL1) & MPIDR_HWID_BITMASK;
>  }
>  
> +static inline u64 kvm_vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, int reg)
> +{
> +	if (has_vhe())
> +		return vcpu_read_sys_reg(vcpu, reg);
> +
> +	return __vcpu_sys_reg(vcpu, reg);
> +}
> +
> +static inline void kvm_vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg)
> +{
> +	if (has_vhe())
> +		vcpu_write_sys_reg(vcpu, val, reg);
> +	else
> +		__vcpu_assign_sys_reg(vcpu, reg, val);
> +}
> +

Can you instead name the wrappers vcpu_{read,write}_sys_reg() and rename
the current implementations, like __vcpu_{read,write}_sysreg_vhe()?

Just want to avoid confusion between kvm_vcpu_ and vcpu_

Thanks,
Oliver