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This project details the process of activating SR-IOV (Single-Root I/O Virtualization) on the iGPU (integrated GPU) of the Radxa X4 board. The goal is to create a VF (Virtual Function) to perform a passthrough of this GPU to a Windows virtual machine (VM). The VM is then used to run games and graphical applications, with the video output captured and displayed on the Linux host machine using the Looking Glass tool.

Activating SR-IOV on integrated GPUs is a technical challenge, and documentation for the Radxa X4 is scarce. This project serves as a detailed, step-by-step guide to help other users with the same setup replicate the process and leverage the graphical performance of the iGPU in a VM without needing a second dedicated graphics card. Using a GPU in a VM also helps decrease the load on the processor, making it a more practical solution for VDI (Virtual Desktop Infrastructure) applications.

• Radxa X4: The motherboard used as the host.
• SR-IOV: A virtualization feature that allows a single PCIe device (the GPU) to be shared among multiple VMs as if they were separate devices.
• Windows VM: The virtual machine where the GPU's VF will be used.
• GPU Passthrough: The process of giving a VM direct and exclusive access to a GPU's VF.
• Looking Glass: A low-latency tool that captures the VM's framebuffer and displays it on the host, allowing the VM to be used as if it were a native application on the Linux desktop.

To follow this guide, you will need the following items:

• Radxa X4 board (with an updated BIOS that supports SR-IOV).
• A Linux operating system (recommended distributions: Arch Linux or Ubuntu Server). This project was tested on a distribution called Cachy OS, which is based on Arch.
• Virtualization tools like QEMU/KVM and libvirt.
• Basic knowledge of the Linux command line.
• The Looking Glass tool (compiled from source or installed via a repository).

The first step is to ensure that SR-IOV is enabled in your Radxa X4's BIOS. Reboot the board and enter the BIOS. Look for and enable the following options:

• Intel VT-d

Save the settings and reboot.

Additionally, for the passthrough to work correctly, the IntelGopDriver.efi driver file is required. The only way to obtain it is by extracting it directly from your BIOS. Use a tool like UEFItool to extract the driver and place it in a location accessible to your VM.

1. Enable SR-IOV in the Kernel: Edit the /etc/default/grub file on the GRUB_CMDLINE_LINUX_DEFAULT line.

   GRUB_CMDLINE_LINUX_DEFAULT='intel_iommu=on i915.enable_guc=3 i915.max_vfs=7 i915.enable_fbc=0 apparmor=1 security=apparmor'

   Parameter Explanations:

   • intel_iommu=on: Activates the IOMMU (Input/Output Memory Management Unit) for Intel processors, which is essential for PCI Passthrough.
   • i915.enable_guc=3: Enables the use of the GuC (Graphics micro-controller) firmware for the Intel i915 GPU, crucial for virtualization. A value of 3 activates task scheduling and firmware loading.
   • i915.max_vfs=7: Specifies that the GPU can create 7 Virtual Functions, allowing each one to be assigned to a different VM.
   • i915.enable_fbc=0: Disables Frame Buffer Compression (FBC) to prevent compatibility and stability issues during passthrough.
   • apparmor=1 security=apparmor: Enables the AppArmor security module in the kernel to enforce access control policies.

   Update GRUB:

   sudo update-grub

2. Verify IOMMU and VFs: After rebooting, check if IOMMU is active and if the GPU has been partitioned into VFs.

   dmesg | grep -i iommu
   lspci -nnk

   You should see your GPU listed with the iommu group and the VFs that have been created.

3. Configure the VM in libvirt: The hostdev section in the XML is the most critical part, as it configures the passthrough of the GPU's VF to the VM.

   • hostdev Device: Adds a hostdev device for the passthrough of a PCI device from the host to the VM.
   • Device Address: The address (address domain="0x0000" bus="0x00" slot="0x02" function="0x2") is the specific address of the iGPU's VF, obtained using the lspci command.
   • vfio Driver: The VFIO driver is used to allow the VM secure, direct access to the device.
   • GPU BIOS ROM (IntelGopDriver.efi): The line rom bar="on" file="/home/${user}/Downloads/IntelGopDriver.efi" injects the driver file extracted from your BIOS, which is essential for the VM to boot with the GPU.

This project uses an XML configuration file for the virtual machine, which contains the specific settings required for GPU passthrough and Looking Glass integration. The most important sections are:

The <devices> section defines the GPU passthrough. The vfio driver is used to isolate the Virtual Function (VF) of the GPU from the host, and the VF's address is specified.

<hostdev mode="subsystem" type="pci" managed="yes">
  <driver name="vfio"/>
  <source>
    <address domain="0x0000" bus="0x00" slot="0x02" function="0x2"/>
  </source>
  <rom bar="on" file="/home/${user}/Downloads/IntelGopDriver.efi"/>
  <address type="pci" domain="0x0000" bus="0x06" slot="0x00" function="0x0"/>
</hostdev>

It is crucial to note the <rom> line, which injects the IntelGopDriver.efi file into the VM. This file is extracted from your BIOS and is essential for the GPU passthrough to work correctly.

For communication between the VM and the host, ivshmem is configured via the QEMU command line.

<qemu:commandline>
  <qemu:arg value="-device"/>
  <qemu:arg value="ivshmem-plain,memdev=ivshmem"/>
  <qemu:arg value="-object"/>
  <qemu:arg value="memory-backend-file,id=ivshmem,share=on,mem-path=/dev/kvmfr0,size=128M"/>
</qemu:commandline>

This configuration creates a shared memory space (/dev/kvmfr0) that the Looking Glass client on the host uses to read the VM's framebuffer with low latency.

To ensure the VM uses the real GPU and not the virtual one, the virtual video card is disabled.

<video>
  <model type="none"/>
</video>

1. On the Windows VM: Install the GPU drivers and the Looking Glass client (looking-glass-client.exe). Make sure the VM is configured to have Looking Glass active on startup.

2. On the Linux Host: Execute looking-glass-client to connect to the VM.

   looking-glass-client -f /dev/kvmfr0

   The client will connect to the VM and display its screen in a window on your Linux desktop, allowing you to interact with the VM as if it were a native application.

Contributions are always welcome! If you find an error or have a suggestion for an improvement, feel free to open an issue or submit a pull request.