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+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.
+
+1. GROUP: KVM_S390_VM_MEM_CTRL
+Architectures: s390
+
+1.1. ATTRIBUTE: KVM_S390_VM_MEM_CTRL
+Parameters: none
+Returns: -EBUSY if already a vcpus is defined, otherwise 0
+
+Enables CMMA for the virtual machine
+
+1.2. ATTRIBUTE: KVM_S390_VM_CLR_CMMA
+Parameteres: none
+Returns: 0
+
+Clear the CMMA status for all guest pages, so any pages the guest marked
+as unused are again used any may not be reclaimed by the host.