[RFC PATCH v2 24/38] KVM: arm64: Respect virtual HCR_EL2.TWX setting

[Jintack Lim]

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@xxxxxxxxxx>
---
 arch/arm64/include/asm/kvm_host.h |  1 +
 arch/arm64/kvm/handle_exit.c      | 13 ++++++++++++-
 arch/arm64/kvm/nested.c           | 20 ++++++++++++++++++++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 46880c3..53b0b33 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -442,5 +442,6 @@ static inline void __cpu_init_stage2(void)
 int __init kvmarm_nested_cfg(char *buf);
 int init_nested_virt(void);
 bool nested_virt_in_use(struct kvm_vcpu *vcpu);
+int handle_wfx_nested(struct kvm_vcpu *vcpu, bool is_wfe);
 
 #endif /* __ARM64_KVM_HOST_H__ */
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 8b398b2..25ec824 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -107,7 +107,18 @@ static int handle_no_fpsimd(struct kvm_vcpu *vcpu, struct kvm_run *run)
  */
 static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
 {
-	if (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WFx_ISS_WFE) {
+	bool is_wfe = !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WFx_ISS_WFE);
+
+	if (nested_virt_in_use(vcpu)) {
+		int ret = handle_wfx_nested(vcpu, is_wfe);
+
+		if (ret < 0 && ret != -EINVAL)
+			return ret;
+		else if (ret >= 0)
+			return ret;
+	}
+
+	if (is_wfe) {
 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
 		vcpu->stat.wfe_exit_stat++;
 		kvm_vcpu_on_spin(vcpu);
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 9a05c76..042d304 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -18,6 +18,8 @@
 #include <linux/kvm.h>
 #include <linux/kvm_host.h>
 
+#include <asm/kvm_emulate.h>
+
 static bool nested_param;
 
 int __init kvmarm_nested_cfg(char *buf)
@@ -41,3 +43,21 @@ bool nested_virt_in_use(struct kvm_vcpu *vcpu)
 
 	return false;
 }
+
+/*
+ * Inject wfx to the virtual EL2 if this is not from the virtual EL2 and
+ * the virtual HCR_EL2.TWX is set. Otherwise, let the host hypervisor
+ * handle this.
+ */
+int handle_wfx_nested(struct kvm_vcpu *vcpu, bool is_wfe)
+{
+	u64 hcr_el2 = vcpu_sys_reg(vcpu, HCR_EL2);
+
+	if (vcpu_mode_el2(vcpu))
+		return -EINVAL;
+
+	if ((is_wfe && (hcr_el2 & HCR_TWE)) || (!is_wfe && (hcr_el2 & HCR_TWI)))
+		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
+
+	return -EINVAL;
+}
-- 
1.9.1