KVM: x86/xen: add KVM_XEN_HVM_SET_ATTR/KVM_XEN_HVM_GET_ATTR

This will be used to set up shared info pages etc.
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>

arch/x86/kvm/x86.c

@@ -5630,6 +5630,26 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		r = kvm_xen_hvm_config(kvm, &xhc);
 		break;
 	}
+	case KVM_XEN_HVM_GET_ATTR: {
+		struct kvm_xen_hvm_attr xha;
+
+		r = -EFAULT;
+		if (copy_from_user(&xha, argp, sizeof(xha)))
+			goto out;
+		r = kvm_xen_hvm_get_attr(kvm, &xha);
+		if (!r && copy_to_user(argp, &xha, sizeof(xha)))
+			r = -EFAULT;
+		break;
+	}
+	case KVM_XEN_HVM_SET_ATTR: {
+		struct kvm_xen_hvm_attr xha;
+
+		r = -EFAULT;
+		if (copy_from_user(&xha, argp, sizeof(xha)))
+			goto out;
+		r = kvm_xen_hvm_set_attr(kvm, &xha);
+		break;
+	}
 	case KVM_SET_CLOCK: {
 		struct kvm_clock_data user_ns;
 		u64 now_ns;

arch/x86/kvm/xen.c

@@ -18,6 +18,36 @@
 
 DEFINE_STATIC_KEY_DEFERRED_FALSE(kvm_xen_enabled, HZ);
 
+int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
+{
+	int r = -ENOENT;
+
+	mutex_unlock(&kvm->lock);
+
+	switch (data->type) {
+	default:
+		break;
+	}
+
+	mutex_unlock(&kvm->lock);
+	return r;
+}
+
+int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
+{
+	int r = -ENOENT;
+
+	mutex_lock(&kvm->lock);
+
+	switch (data->type) {
+	default:
+		break;
+	}
+
+	mutex_unlock(&kvm->lock);
+	return r;
+}
+
 int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data)
 {
 	struct kvm *kvm = vcpu->kvm;

arch/x86/kvm/xen.h

@@ -13,6 +13,8 @@
 
 extern struct static_key_false_deferred kvm_xen_enabled;
 
+int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data);
+int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data);
 int kvm_xen_hypercall(struct kvm_vcpu *vcpu);
 int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data);
 int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc);

include/uapi/linux/kvm.h

@@ -1587,6 +1587,17 @@ struct kvm_pv_cmd {
 /* Available with KVM_CAP_DIRTY_LOG_RING */
 #define KVM_RESET_DIRTY_RINGS		_IO(KVMIO, 0xc7)
 
+#define KVM_XEN_HVM_GET_ATTR	_IOWR(KVMIO, 0xc8, struct kvm_xen_hvm_attr)
+#define KVM_XEN_HVM_SET_ATTR	_IOW(KVMIO,  0xc9, struct kvm_xen_hvm_attr)
+
+struct kvm_xen_hvm_attr {
+	__u16 type;
+	__u16 pad[3];
+	union {
+		__u64 pad[8];
+	} u;
+};
+
 /* Secure Encrypted Virtualization command */
 enum sev_cmd_id {
 	/* Guest initialization commands */