Subject: [PATCH v2 03/94] KVM: arm64: nv: Introduce nested virtualization VCPU feature

From: Marc Zyngier <[email-masked]>
Date: Tue, 11 Feb 2020 17:48:07 +0000

From: Christoffer Dall <[email-masked]>

Introduce the feature bit and a primitive that checks if the feature is
set behind a static key check based on the cpus_have_const_cap check.

Checking nested_virt_in_use() on systems without nested virt enabled
should have neglgible overhead.

We don't yet allow userspace to actually set this feature.

Signed-off-by: Christoffer Dall <[email-masked]>
Signed-off-by: Marc Zyngier <[email-masked]>
---
 arch/arm/include/asm/kvm_nested.h   |  9 +++++++++
 arch/arm64/include/asm/kvm_nested.h | 13 +++++++++++++
 arch/arm64/include/uapi/asm/kvm.h   |  1 +
 3 files changed, 23 insertions(+)
 create mode 100644 arch/arm/include/asm/kvm_nested.h
 create mode 100644 arch/arm64/include/asm/kvm_nested.h

diff --git a/arch/arm/include/asm/kvm_nested.h b/arch/arm/include/asm/kvm_nested.h
new file mode 100644
index 000000000000..124ff6445f8f
--- /dev/null
+++ b/arch/arm/include/asm/kvm_nested.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARM_KVM_NESTED_H
+#define __ARM_KVM_NESTED_H
+
+#include <linux/kvm_host.h>
+
+static inline bool nested_virt_in_use(const struct kvm_vcpu *vcpu) { return false; }
+
+#endif /* __ARM_KVM_NESTED_H */
diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
new file mode 100644
index 000000000000..f243a8acb9fc
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARM64_KVM_NESTED_H
+#define __ARM64_KVM_NESTED_H
+
+#include <linux/kvm_host.h>
+
+static inline bool nested_virt_in_use(const struct kvm_vcpu *vcpu)
+{
+	return cpus_have_const_cap(ARM64_HAS_NESTED_VIRT) &&
+		test_bit(KVM_ARM_VCPU_HAS_EL2, vcpu->arch.features);
+}
+
+#endif /* __ARM64_KVM_NESTED_H */
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index ba85bb23f060..5b9c58a55537 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -106,6 +106,7 @@ struct kvm_regs {
 #define KVM_ARM_VCPU_SVE		4 /* enable SVE for this CPU */
 #define KVM_ARM_VCPU_PTRAUTH_ADDRESS	5 /* VCPU uses address authentication */
 #define KVM_ARM_VCPU_PTRAUTH_GENERIC	6 /* VCPU uses generic authentication */
+#define KVM_ARM_VCPU_HAS_EL2		7 /* Support nested virtualization */
 
 struct kvm_vcpu_init {
 	__u32 target;
-- 
2.20.1

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