Device configuration in DPM mode

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7.1 DPM partition

As of z14 and IBM® LinuxONE II, with an IBM® Z or IBM® LinuxONE machine running in Dynamic Partition Manager (DPM) mode, device configuration data are stored on the Support Element (SE).

Device configuration data is defined by user input through the hardware management console (HMC) interface in DPM mode, or by pre-defined DPM firmware values. Such data for channel-attached CCW devices and PCI FIDs is stored on the Support Element (SE) and processed automatically by Linux® during the boot process.

Make devices available on DPM

The IBM® Z or IBM LinuxONE firmware automatically processes the device-configuration data you provide on the HMC or SE interface, and creates and activates a corresponding IOCDS for you.

Note: For CCW devices, a newly added device might not become visible in Linux if all associated CHPIDs are offline. In such situations, you must manually enable the relevant CHPID, either from within Linux or through the HMC. For PCI FIDs, the system applies changes immediately, and the devices become available without additional steps.

chzdev provides a richer set of configuration options than the HMC interface. The active and persistent settings are often a fine-tuned version of the auto-configuration.

Special considerations when using cio_ignore with auto-configuration

In PR/SM mode, the cio_ignore mechanism works strictly as specified on the Linux kernel command line. When users activate cio_ignore by adding it to the kernel parameters, Linux keeps all listed channel-attached CCW devices unavailable until the user explicitly removes them from the ignore list.

In DPM mode, however, auto‑configuration changes this behavior. During boot, DPM provides Linux with auto‑configuration data, and Linux automatically removes any auto‑configured device from the cio_ignore list, effectively overriding the user‑defined settings. As a result, the only way to preserve a user‑specified cio_ignore list in DPM partitions is to disable auto‑configuration by using the rd.zdev=no-auto kernel parameter. This parameter also affects the initial online state of PCIe devices and cryptographic devices, see rd.zdev=no-auto - Override initial device availability for DPM mode.