[RFC PATCH v2 04/38] KVM: arm/arm64: Check if nested virtualization is in use

[Jintack Lim]

Nested virtualizaion is in use only if all three conditions are met:
- The architecture supports nested virtualization.
- The kernel parameter is set.
- The userspace uses nested virtualiztion feature.

Signed-off-by: Jintack Lim <jintack.lim@xxxxxxxxxx>
---
 arch/arm/include/asm/kvm_host.h   | 11 +++++++++++
 arch/arm64/include/asm/kvm_host.h |  2 ++
 arch/arm64/kvm/nested.c           | 17 +++++++++++++++++
 virt/kvm/arm/arm.c                |  4 ++++
 4 files changed, 34 insertions(+)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 00b0f97..7e9e6c8 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -303,4 +303,15 @@ static inline int __init kvmarm_nested_cfg(char *buf)
 {
 	return 0;
 }
+
+static inline int init_nested_virt(void)
+{
+	return 0;
+}
+
+static inline bool nested_virt_in_use(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+
 #endif /* __ARM_KVM_HOST_H__ */
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 6df0c7c..86d4b6c 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -387,5 +387,7 @@ 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);
 
 #endif /* __ARM64_KVM_HOST_H__ */
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 79f38da..9a05c76 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -24,3 +24,20 @@ int __init kvmarm_nested_cfg(char *buf)
 {
 	return strtobool(buf, &nested_param);
 }
+
+int init_nested_virt(void)
+{
+	if (nested_param && cpus_have_const_cap(ARM64_HAS_NESTED_VIRT))
+		kvm_info("Nested virtualization is supported\n");
+
+	return 0;
+}
+
+bool nested_virt_in_use(struct kvm_vcpu *vcpu)
+{
+	if (nested_param && cpus_have_const_cap(ARM64_HAS_NESTED_VIRT)
+	    && test_bit(KVM_ARM_VCPU_NESTED_VIRT, vcpu->arch.features))
+		return true;
+
+	return false;
+}
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 1c1c772..36aae3a 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -1478,6 +1478,10 @@ int kvm_arch_init(void *opaque)
 	if (err)
 		goto out_err;
 
+	err = init_nested_virt();
+	if (err)
+		return err;
+
 	err = init_subsystems();
 	if (err)
 		goto out_hyp;
-- 
1.9.1