System requirements

BIOS configuration

AMD platforms

  • SPM(Special Purpose Memory) configuration

    AMD CBS → CXL Common Options → CXL Memory Attribute : Enabled
    Warning
    If disabled, the CXL memory lacks EFI_MEMORY_SP attribute, causing the OS to boot it as standard system-ram(CPU-less NUMA node via SRAT).
    Once it is integrated into system memory, it cannot be reconfigured to DAX.

  • Use CPU address space

    AMD CBS → CXL Common Options → CXL Physical Addressing : System address
    Warning
    If not set to System address, a mismatch between SPA(System Physical Address) and HPA(Host Physical Address) occurs.
    It prevents the HDM(Host-managed Device Memory) Decoder from validating the memory range, making it impossible to create CXL Region.
    Without a valid region, the memory cannot be assigned to DAX.

  • Enable MSI multi vector

    AMD CBS → NBIO Common Options → IOMMU/Security → IOMMU : Enabled
    Warning
    If disabled, Interrupt Remapping is unavailable, limiting the CXL device to a single MSI vector.
    But our device is using multi vector MSI, so it should be enabled.

OS

  • Ubuntu 24.04.3 LTS

Kernel boot parameter for CXL devdax

  • Add memhp_default_state=offline to the kernel boot parameters

    Why? When CXL memory is onlined as system-ram, the kernel automatically manages it as regular memory. Setting memhp_default_state=offline prevents the kernel from auto-onlining hot-plugged memory, allowing it to remain available for devdax configuration.

GRUB configuration
  1. Edit the GRUB configuration file: 
    sudo vi /etc/default/grub
  2. Append memhp_default_state=offline to the GRUB_CMDLINE_LINUX variable: 
    GRUB_CMDLINE_LINUX="memhp_default_state=offline"

    Note If GRUB_CMDLINE_LINUX already contains other parameters, append memhp_default_state=offline with a space separator. Do not remove the existing parameters.

  3. Update GRUB and reboot: 
    sudo update-grub
sudo reboot
  4. After reboot, verify the parameter is applied: 
    cat /proc/cmdline | grep memhp_default_state

Required APT packages 

build-essential cmake ninja-build wget
python3-dev python3-pip python3-venv libncurses6
libglib2.0-0 libslirp0 liburing2 libcurl3-gnutls

Required Python packages 

numpy tomli capstone cxxfilt pyelftools

Docker

  • Optional, recommended for consistent build environments

    Note
    For non-Ubuntu systems, it is recommended to use the official Docker image to ensure full compatibility.