Worked on the zephyrproject-rtos/zephyr-testing repository to address a multi-processor configuration issue in x86_64 platforms by correcting Devicetree CPU nodes. Focused on embedded systems, the developer identified missing CPU nodes for ACRN, Bartlett Lake S, and Elkhart Lake, aligning the device tree source (DTS) files with CONFIG_MP_MAX_NUM_CPUS. This fix improved symmetric multiprocessing (SMP) reliability and enhanced boot stability across affected platforms. The work required a detailed understanding of device tree structures and embedded hardware configuration, resulting in reduced runtime misbehavior and more robust multi-processor support for these specific x86_64 environments within the Zephyr testing framework.