KVM: arm64: nv: Introduce nested virtualization VCPU feature

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 vcpu_has_nv() on systems without nested virt enabled
should have negligible overhead.

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

Reviewed-by: Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230209175820.1939006-4-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
new file mode 100644 (file)
index 0000000..fd601ea
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARM64_KVM_NESTED_H
+#define __ARM64_KVM_NESTED_H
+
+#include <linux/kvm_host.h>
+
+static inline bool vcpu_has_nv(const struct kvm_vcpu *vcpu)
+{
+       return (!__is_defined(__KVM_NVHE_HYPERVISOR__) &&
+               cpus_have_final_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 a7a857f1784d80d6264eeebecbeb371c7d13ba5b..f8129c624b0709815cbd266d569bb12fb70e6047 100644 (file)
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -109,6 +109,7 @@ 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;