KVM: arm64: nv: Respect virtual HCR_EL2.TWx setting

Forward exceptions due to WFI or WFE instructions to the virtual EL2 if
they are not coming from the virtual EL2 and virtual HCR_EL2.TWx is set.

Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250225172930.1850838-12-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

Author: soccertack

arch/arm64/include/asm/kvm_emulate.h

@@ -275,6 +275,19 @@ static __always_inline u64 kvm_vcpu_get_esr(const struct kvm_vcpu *vcpu)
 	return vcpu->arch.fault.esr_el2;
 }
 
+static inline bool guest_hyp_wfx_traps_enabled(const struct kvm_vcpu *vcpu)
+{
+	u64 esr = kvm_vcpu_get_esr(vcpu);
+	bool is_wfe = !!(esr & ESR_ELx_WFx_ISS_WFE);
+	u64 hcr_el2 = __vcpu_sys_reg(vcpu, HCR_EL2);
+
+	if (!vcpu_has_nv(vcpu) || vcpu_is_el2(vcpu))
+		return false;
+
+	return ((is_wfe && (hcr_el2 & HCR_TWE)) ||
+		(!is_wfe && (hcr_el2 & HCR_TWI)));
+}
+
 static __always_inline int kvm_vcpu_get_condition(const struct kvm_vcpu *vcpu)
 {
 	u64 esr = kvm_vcpu_get_esr(vcpu);

arch/arm64/kvm/handle_exit.c

@@ -129,8 +129,12 @@ static int kvm_handle_fpasimd(struct kvm_vcpu *vcpu)
 static int kvm_handle_wfx(struct kvm_vcpu *vcpu)
 {
 	u64 esr = kvm_vcpu_get_esr(vcpu);
+	bool is_wfe = !!(esr & ESR_ELx_WFx_ISS_WFE);
 
-	if (esr & ESR_ELx_WFx_ISS_WFE) {
+	if (guest_hyp_wfx_traps_enabled(vcpu))
+		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_esr(vcpu));
+
+	if (is_wfe) {
 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
 		vcpu->stat.wfe_exit_stat++;
 	} else {