default or selected kernelversion does not have config value CONFIG_LUSTRE_OBD_MAX_IOCTL_BUFFER.
Result is shown for kernelversion 6.5.1

Lustre obd max ioctl buffer bytes (default 8KB)


Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>Lustre obd max ioctl buffer bytes (default 8KB)
In linux kernel since version 3.11 (release Date: 2013-09-02)  
This option defines the maximum size of buffer in bytes that user space
applications can pass to Lustre kernel module through ioctl interface.

If unsure, use default.