KVM: s390: Per-vm kvm device controls

We sometimes need to get/set attributes specific to a virtual machine
and so need something else than ONE_REG.

Let's copy the KVM_DEVICE approach, and define the respective ioctls
for the vm file descriptor.
Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

Documentation/virtual/kvm/api.txt

@@ -2314,8 +2314,8 @@ struct kvm_create_device {
 
 4.80 KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR
 
-Capability: KVM_CAP_DEVICE_CTRL
-Type: device ioctl
+Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device
+Type: device ioctl, vm ioctl
 Parameters: struct kvm_device_attr
 Returns: 0 on success, -1 on error
 Errors:
@@ -2340,8 +2340,8 @@ struct kvm_device_attr {
 
 4.81 KVM_HAS_DEVICE_ATTR
 
-Capability: KVM_CAP_DEVICE_CTRL
-Type: device ioctl
+Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device
+Type: device ioctl, vm ioctl
 Parameters: struct kvm_device_attr
 Returns: 0 on success, -1 on error
 Errors:

Documentation/virtual/kvm/devices/vm.txt

+Generic vm interface
+====================================
+
+The virtual machine "device" also accepts the ioctls KVM_SET_DEVICE_ATTR,
+KVM_GET_DEVICE_ATTR, and KVM_HAS_DEVICE_ATTR. The interface uses the same
+struct kvm_device_attr as other devices, but targets VM-wide settings
+and controls.
+
+The groups and attributes per virtual machine, if any, are architecture
+specific.

arch/s390/kvm/kvm-s390.c

@@ -162,6 +162,7 @@ int kvm_dev_ioctl_check_extension(long ext)
 	case KVM_CAP_IOEVENTFD:
 	case KVM_CAP_DEVICE_CTRL:
 	case KVM_CAP_ENABLE_CAP_VM:
+	case KVM_CAP_VM_ATTRIBUTES:
 		r = 1;
 		break;
 	case KVM_CAP_NR_VCPUS:
@@ -257,11 +258,43 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
 	return r;
 }
 
+static int kvm_s390_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	int ret;
+
+	switch (attr->group) {
+	default:
+		ret = -ENXIO;
+		break;
+	}
+
+	return ret;
+}
+
+static int kvm_s390_vm_get_attr(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	return -ENXIO;
+}
+
+static int kvm_s390_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	int ret;
+
+	switch (attr->group) {
+	default:
+		ret = -ENXIO;
+		break;
+	}
+
+	return ret;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
 	struct kvm *kvm = filp->private_data;
 	void __user *argp = (void __user *)arg;
+	struct kvm_device_attr attr;
 	int r;
 
 	switch (ioctl) {
@@ -294,6 +327,27 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		}
 		break;
 	}
+	case KVM_SET_DEVICE_ATTR: {
+		r = -EFAULT;
+		if (copy_from_user(&attr, (void __user *)arg, sizeof(attr)))
+			break;
+		r = kvm_s390_vm_set_attr(kvm, &attr);
+		break;
+	}
+	case KVM_GET_DEVICE_ATTR: {
+		r = -EFAULT;
+		if (copy_from_user(&attr, (void __user *)arg, sizeof(attr)))
+			break;
+		r = kvm_s390_vm_get_attr(kvm, &attr);
+		break;
+	}
+	case KVM_HAS_DEVICE_ATTR: {
+		r = -EFAULT;
+		if (copy_from_user(&attr, (void __user *)arg, sizeof(attr)))
+			break;
+		r = kvm_s390_vm_has_attr(kvm, &attr);
+		break;
+	}
 	default:
 		r = -ENOTTY;
 	}

include/uapi/linux/kvm.h

@@ -743,6 +743,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_IOAPIC_POLARITY_IGNORED 97
 #define KVM_CAP_ENABLE_CAP_VM 98
 #define KVM_CAP_S390_IRQCHIP 99
+#define KVM_CAP_VM_ATTRIBUTES 100
 
 #ifdef KVM_CAP_IRQ_ROUTING