[PATCH v4 11/16] KVM: arm64: nv: Respect virtual HCR_EL2.TWx setting

Marc Zyngier
2025-02-25T17:29:47Z

From: Jintack Lim <jintack.lim@linaro.org>

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>
---
arch/arm64/include/asm/kvm_emulate.h | 13 +++++++++++++
arch/arm64/kvm/handle_exit.c | 6 +++++-
2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 78ec1ef2cfe82..d4e4212ff5967 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/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);
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 512d152233ff2..b73dc26bc44b4 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/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 {
--
2.39.2