Types of paravirtualized CCW devices

SUSE Linux Enterprise Server 15 SP5 KVM guest

For Linux® as a KVM guest on IBM® Z, paravirtualized CCW devices can represent various real and virtual devices, including block devices, network devices, and devices that are attached through a virtual SCSI HBA.

Table 1 explains the values that are shown in the CU Type column of the lscss command. Which of these devices are present on a particular KVM guest depends on the virtual server configuration on the KVM hypervisor.
Table 1. Types of paravirtualized CCW devices
CU Type/Model Explanation
3832/01 Network device

The corresponding device bus-ID represents a network interface on the guest. The details of the interface are hidden by the KVM hypervisor. On the KVM hypervisor, this interface might be based on a MacVTap interface or a virtual switch.

Network devices are handled by the virtio_net device driver module. See Virtual network devices for details.
3832/02 Block device

The corresponding device bus-ID represents a persistent storage space to the guest. The details of the block device are hidden by the KVM hypervisor. To the KVM hypervisor, this storage space might be a SCSI LUN or a DASD, but it might also be a file in the file system of the host or any other block device.

Block devices are handled by the virtio_blk device driver module. See Virtual block devices for details.
3832/03 Character device for console output. See Using virsh on a KVM host.
3832/04 Random number generator device

Depending on the configuration of your virtual server by the KVM hypervisor, this device might be backed by IBM Z® cryptographic hardware.

This device provides sufficient random numbers of good quality only if the random device of KVM host does so. In particular, this devices provides true random numbers only if it is backed by a true random number generator on the KVM host.

This device is provided by the virtio_rng device driver module.
3832/05 Balloon device for memory management.

The preferred memory management technology is Collaborative Memory Management Assist (CMMA). See cmma - Reduce hypervisor paging I/O overhead.
3832/08 Virtual SCSI HBA
SCSI devices can be attached through a virtual SCSI host bus adapter (HBA) and are then handled by the virtio_scsi device driver module. For example, the following devices are attached through a virtual SCSI HBA:

Host devices need not necessarily be attached through a virtual SCSI HBA. For example, SCSI-attached disks are usually virtualized as block devices and handled by the virtio_blk device driver module.
3832/10 Virtual graphics processing unit (GPU). Supports remote access to graphical user interfaces. GPU devices are handled by the virtio_gpu device driver module.
3832/12 Virtual human interface devices, like a virtual keyboard and a virtual mouse, as remote input devices for graphical user interfaces. These devices are handled by the virtio_input device driver module.
3832/13 Devices for communications between applications on the guest and on the host. For example, hypervisor services can use these devices to communicate with guest agents. These devices are handled by the virtio_vsock device driver module.