Re: [PATCH v4 20/36] KVM: arm64: Disable hierarchical permissions when S1PIE is enabled

[Oliver Upton <oliver.upton@linux.dev>]

On Wed, Oct 09, 2024 at 08:00:03PM +0100, Marc Zyngier wrote:
> S1PIE implicitly disables hierarchical permissions, as specified in
> R_JHSVW, by making TCR_ELx.HPDn RES1.
> 
> Add a predicate for S1PIE being enabled for a given translation regime,
> and emulate this behaviour by forcing the hpd field to true if S1PIE
> is enabled for that translation regime.
> 
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/kvm/at.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
> index adcfce3f67f03..f5bd750288ff5 100644
> --- a/arch/arm64/kvm/at.c
> +++ b/arch/arm64/kvm/at.c
> @@ -93,6 +93,23 @@ static enum trans_regime compute_translation_regime(struct kvm_vcpu *vcpu, u32 o
>  	}
>  }
>  
> +static bool s1pie_enabled(struct kvm_vcpu *vcpu, enum trans_regime regime)
> +{
> +	if (!kvm_has_feat(vcpu->kvm, ID_AA64MMFR3_EL1, S1PIE, IMP))
> +		return false;
> +
> +	switch (regime) {
> +	case TR_EL2:
> +	case TR_EL20:
> +		return vcpu_read_sys_reg(vcpu, TCR2_EL2) & TCR2_EL2_PIE;
> +	case TR_EL10:
> +		return  (__vcpu_sys_reg(vcpu, HCRX_EL2) & HCRX_EL2_TCR2En) &&
> +			(__vcpu_sys_reg(vcpu, TCR2_EL1) & TCR2_EL1x_PIE);
> +	default:
> +		BUG();

BUILD_BUG()?

> +	}
> +}
> +
>  static int setup_s1_walk(struct kvm_vcpu *vcpu, u32 op, struct s1_walk_info *wi,
>  			 struct s1_walk_result *wr, u64 va)
>  {
> @@ -186,6 +203,8 @@ static int setup_s1_walk(struct kvm_vcpu *vcpu, u32 op, struct s1_walk_info *wi,
>  		    (va55 ?
>  		     FIELD_GET(TCR_HPD1, tcr) :
>  		     FIELD_GET(TCR_HPD0, tcr)));
> +	/* R_JHSVW */
> +	wi->hpd |= s1pie_enabled(vcpu, wi->regime);
>  
>  	/* Someone was silly enough to encode TG0/TG1 differently */
>  	if (va55) {
> -- 
> 2.39.2
> 

-- 
Thanks,
Oliver