KVM: arm64: Hoist PAuth checks into KVM_ARM_VCPU_INIT ioctl

Test for feature support in the ioctl handler rather than
kvm_reset_vcpu(). Continue to uphold our all-or-nothing policy with
address and generic pointer authentication.

Link: https://lore.kernel.org/r/20230920195036.1169791-5-oliver.upton@linux.devSigned-off-by: Oliver Upton <oliver.upton@linux.dev>

arch/arm64/kvm/arm.c

@@ -1203,6 +1203,11 @@ static unsigned long system_supported_vcpu_features(void)
 	if (!system_supports_sve())
 		clear_bit(KVM_ARM_VCPU_SVE, &features);
 
+	if (!system_has_full_ptr_auth()) {
+		clear_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, &features);
+		clear_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, &features);
+	}
+
 	return features;
 }
 
@@ -1223,6 +1228,14 @@ static int kvm_vcpu_init_check_features(struct kvm_vcpu *vcpu,
 	if (features & ~system_supported_vcpu_features())
 		return -EINVAL;
 
+	/*
+	 * For now make sure that both address/generic pointer authentication
+	 * features are requested by the userspace together.
+	 */
+	if (test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, &features) !=
+	    test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, &features))
+		return -EINVAL;
+
 	if (!test_bit(KVM_ARM_VCPU_EL1_32BIT, &features))
 		return 0;
 

arch/arm64/kvm/reset.c

@@ -165,20 +165,9 @@ static void kvm_vcpu_reset_sve(struct kvm_vcpu *vcpu)
 		memset(vcpu->arch.sve_state, 0, vcpu_sve_state_size(vcpu));
 }
 
-static int kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu)
+static void kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu)
 {
-	/*
-	 * For now make sure that both address/generic pointer authentication
-	 * features are requested by the userspace together and the system
-	 * supports these capabilities.
-	 */
-	if (!test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, vcpu->arch.features) ||
-	    !test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features) ||
-	    !system_has_full_ptr_auth())
-		return -EINVAL;
-
 	vcpu_set_flag(vcpu, GUEST_HAS_PTRAUTH);
-	return 0;
 }
 
 /**
@@ -233,12 +222,8 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 	}
 
 	if (test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, vcpu->arch.features) ||
-	    test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features)) {
-		if (kvm_vcpu_enable_ptrauth(vcpu)) {
-			ret = -EINVAL;
-			goto out;
-		}
-	}
+	    test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features))
+		kvm_vcpu_enable_ptrauth(vcpu);
 
 	if (vcpu_el1_is_32bit(vcpu))
 		pstate = VCPU_RESET_PSTATE_SVC;