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

On Thu, 10 Oct 2024 08:33:13 +0100,
Oliver Upton [off-list ref] wrote:

On Wed, Oct 09, 2024 at 08:00:03PM +0100, Marc Zyngier wrote:

quoted

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()?

Doesn't work. regime is fished out of the walk_info structure, meaning
that it is pretty opaque to the compiler, which in turn needs to emit
code for all cases.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.