KVM: arm64: Add capability to advertise ptrauth for guest

This patch advertises the capability of two cpu feature called address
pointer authentication and generic pointer authentication. These
capabilities depend upon system support for pointer authentication and
VHE mode.

The current arm64 KVM partially implements pointer authentication and
support of address/generic authentication are tied together. However,
separate ABI requirements for both of them is added so that any future
isolated implementation will not require any ABI changes.
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Documentation/virtual/kvm/api.txt

@@ -2763,13 +2763,19 @@ Possible features:
 
 	- KVM_ARM_VCPU_PTRAUTH_ADDRESS: Enables Address Pointer authentication
 	  for arm64 only.
-	  Both KVM_ARM_VCPU_PTRAUTH_ADDRESS and KVM_ARM_VCPU_PTRAUTH_GENERIC
-	  must be requested or neither must be requested.
+	  Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS.
+	  If KVM_CAP_ARM_PTRAUTH_ADDRESS and KVM_CAP_ARM_PTRAUTH_GENERIC are
+	  both present, then both KVM_ARM_VCPU_PTRAUTH_ADDRESS and
+	  KVM_ARM_VCPU_PTRAUTH_GENERIC must be requested or neither must be
+	  requested.
 
 	- KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication
 	  for arm64 only.
-	  Both KVM_ARM_VCPU_PTRAUTH_ADDRESS and KVM_ARM_VCPU_PTRAUTH_GENERIC
-	  must be requested or neither must be requested.
+	  Depends on KVM_CAP_ARM_PTRAUTH_GENERIC.
+	  If KVM_CAP_ARM_PTRAUTH_ADDRESS and KVM_CAP_ARM_PTRAUTH_GENERIC are
+	  both present, then both KVM_ARM_VCPU_PTRAUTH_ADDRESS and
+	  KVM_ARM_VCPU_PTRAUTH_GENERIC must be requested or neither must be
+	  requested.
 
 	- KVM_ARM_VCPU_SVE: Enables SVE for the CPU (arm64 only).
 	  Depends on KVM_CAP_ARM_SVE.

arch/arm64/kvm/reset.c

@@ -101,6 +101,11 @@ int kvm_arch_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_ARM_SVE:
 		r = system_supports_sve();
 		break;
+	case KVM_CAP_ARM_PTRAUTH_ADDRESS:
+	case KVM_CAP_ARM_PTRAUTH_GENERIC:
+		r = has_vhe() && system_supports_address_auth() &&
+				 system_supports_generic_auth();
+		break;
 	default:
 		r = 0;
 	}

include/uapi/linux/kvm.h

@@ -989,6 +989,8 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_MANUAL_DIRTY_LOG_PROTECT 166
 #define KVM_CAP_HYPERV_CPUID 167
 #define KVM_CAP_ARM_SVE 168
+#define KVM_CAP_ARM_PTRAUTH_ADDRESS 169
+#define KVM_CAP_ARM_PTRAUTH_GENERIC 170
 
 #ifdef KVM_CAP_IRQ_ROUTING