IBM Z mainframe networking (OSA-Express, HiperSockets, ISM, CTCM, IUCV)
Networking drivers specific to IBM Z and LinuxONE mainframes: OSA-Express Ethernet adapters and in-memory HiperSockets (qeth), Internal Shared Memory devices used by SMC-D for fast guest-to-guest traffic (ism), and the older CTCM and IUCV channel links inherited from the VM lineage. These are how Linux guests on z/VM, KVM on Z, and LPARs reach the network and each other.
recommendation
It should stay in the kernel because IBM still ships and sells the underlying hardware on current z16 and z17 mainframes in 2025, IBM's own Linux-on-Z documentation points customers at exactly these drivers (qeth for OSA-Express and HiperSockets, ism for SMC-D), and upstream activity on files like qeth_core_main.c shows ongoing maintenance rather than bit-rot. Removing them would break a small but real enterprise installed base with no alternative driver.
repository signals
sources
- lore.kernel.org
Recent upstream patch traffic still touches drivers/s390/net/qeth_core_main.c, indicating ongoing maintenance rather than abandonment.
- ibm.com
IBM documents qeth as the current driver for OSA-Express, HiperSockets, guest LANs, and z/VM virtual switches, and the page includes support tables reaching IBM z17 and z16.
- ibm.com
IBM z17 HMC documentation still exposes OSD, HiperSockets, and SMC-D/ISM adapters as configurable current-platform options.
- ibm.com
IBM documents the ISM device driver as the Linux driver for current Internal Shared Memory vPCI devices used for SMC-D on IBM Z/LinuxONE.
codex reasoning notes (technical)
Real driver directory: Kconfig lists CTCM, SMSGIUCV, QETH, and ISM. lore_file_timeline on drivers/s390/net/qeth_core_main.c returned 293 matches since 2021 with newest activity in 2026; cited lore URL came from that MCP tool. IBM deployment evidence came from web search hits on ibm.com: qeth docs show current OSA-Express/HiperSockets/z17-z16 support, z17 HMC docs show OSD/HiperSockets/SMC-D adapters still present, and IBM's ISM driver page shows current Linux support for ISM. A lore_regex removal query timed out and local lei was blocked by socket permissions, so removal-discussion coverage is incomplete, but gathered evidence points to an actively maintained, still-deployed niche enterprise driver family with no obvious upstream replacement.