Re: [PATCH v2 3/4] KVM: arm64: Reset TCR_EL2 according to guest's E2H mode

[Joey Gouly <joey.gouly@arm.com>]

On Thu, Sep 17, 2026 at 10:42:13PM +0100, Wei-Lin Chang wrote:
> From: Marc Zyngier <maz@kernel.org>
> 
> Previously vCPU TCR_EL2's reset value didn't consider TCR_EL2's
> different formats based on the value of HCR_EL2.E2H. It always resets to
> the E2H == 0 version.
> 
> This didn't cause any problem because the bits set in the E2H == 0
> version (TCR_EL2_RES1) all reset to UNKNOWN for E2H == 1 per the
> architecture.
> 
> Still, it's better to fix it. Choose the correct reset value by checking
> KVM_ARM_VCPU_HAS_EL2_E2H0.
> 
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Signed-off-by: Wei-Lin Chang <weilin.chang@arm.com>

Reviewed-by: Joey Gouly <joey.gouly@arm.com>

> ---
>  arch/arm64/kvm/sys_regs.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 44aae52c473d..62c059747fbb 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -3275,6 +3275,14 @@ static u64 reset_mdcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
>  	return vcpu->kvm->arch.nr_pmu_counters;
>  }
>  
> +static u64 reset_tcr_el2(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> +{
> +	__vcpu_assign_sys_reg(vcpu, r->reg,
> +			      vcpu_has_feature(vcpu, KVM_ARM_VCPU_HAS_EL2_E2H0) ?
> +			      TCR_EL2_RES1 : VHE_TCR_EL2_RES1);
> +	return __vcpu_sys_reg(vcpu, r->reg);
> +}
> +
>  /*
>   * Architected system registers.
>   * Important: Must be sorted ascending by Op0, Op1, CRn, CRm, Op2
> @@ -3853,7 +3861,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  
>  	EL2_REG(TTBR0_EL2, access_rw, reset_val, 0),
>  	EL2_REG(TTBR1_EL2, access_rw, reset_val, 0),
> -	EL2_REG(TCR_EL2, access_rw, reset_val, TCR_EL2_RES1),
> +	EL2_REG(TCR_EL2, access_rw, reset_tcr_el2, 0),
>  	EL2_REG_FILTERED(TCR2_EL2, access_rw, reset_val, TCR2_EL2_RES1,
>  			 tcr2_el2_visibility),
>  	EL2_REG_VNCR(VTTBR_EL2, reset_val, 0),
> -- 
> 2.43.0
>