virtio-ccw transport for IBM Z KVM guests
The virtio transport that lets Linux guests running on KVM on IBM Z mainframes talk to paravirtualized disks, network cards, and other devices using the s390 channel I/O (CCW) model rather than PCI. It is the standard way virtual devices are presented to Linux guests on IBM Z hypervisors.
recommendation
Worth keeping but documenting as niche infrastructure: IBM Z mainframes are still sold and shipped in 2025, and IBM's current documentation confirms virtio-ccw remains the guest transport for KVM on Z. Maintenance commits continue into 2025-2026 with no removal discussions, but the user base is narrow compared with x86 virtio, so it makes sense to flag it as architecture-specific rather than broadly deployed.
repository signals
sources
- ibm.com
IBM documents that KVM on IBM Z virtualizes guest devices as virtio CCW devices, indicating the transport is still part of current IBM Z virtualization deployments.
- ibm.com
IBM's Linux on IBM Z documentation describes the virtio CCW transport driver as the guest transport for KVM-provided virtual CCW devices.
- cateee.net
LKDDb shows current kernel support paths for s390 guest virtio/CCW support and maps `drivers/s390/virtio/virtio_ccw.c` to recent kernel series.
- docs.kernel.org
Kernel documentation describes virtio-ccw handling for s390 KVM guests, showing the transport remains part of the documented virtualization stack.
codex reasoning notes (technical)
Local `sed` inspection showed this directory is the `virtio_ccw` transport driver for ccw-based virtio on s390/IBM Z guests. Local `git log` (with `-c safe.directory=...`) showed ongoing maintenance through 2025-2026 and no directory-specific deprecation/removal commits, so there is no evidence of active upstream removal talk. Web search found current IBM docs and LKDDb pages confirming virtio-ccw is still a live IBM Z KVM guest transport, but deployments are niche rather than broad. Recommendation is `keep-annotate`: keep it upstream, but annotate as low-deployment, architecture-specific virtualization infrastructure rather than broadly deployed hardware.