Re: [PATCH v5 20/37] KVM: arm64: Disable hierarchical permissions when S1PIE is enabled

Joey Gouly
2024-10-24T14:02:51Z

On Wed, Oct 23, 2024 at 03:53:28PM +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>

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

> ---
> 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();
> + }
> +}
> +
> 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
>