AZ-800 Administering Windows Server Hybrid Core Infrastructure Exam

Configure Host and Guest for Discrete Device Assignment

Discrete Device Assignment (DDA) is a Hyper-V feature that lets a virtual machine access a physical PCIe device directly. By using DDA, you can improve performance and gain full hardware acceleration inside a VM. This setup is ideal for workloads that need high throughput or specialized hardware, such as GPUs or network adapters. It also helps maintain security boundaries by isolating devices between the host and guests.

Before assigning a device, you must evaluate hardware compatibility on the Hyper-V host. Use the Device Manager or PowerShell to:

• Identify compatible PCIe devices
• Locate the exact device path
• Confirm that the device is not already in use
  This ensures that the hardware meets the requirements for DDA and prevents conflicts with the host operating system. Proper evaluation lays the groundwork for a smooth assignment process.

Next, prepare the device by dismounting it from the host and marking it as assignable. The steps include:

• Dismounting the device so the host no longer controls it
• Marking it as assignable using Hyper-V Manager or PowerShell cmdlets
• Ensuring the device driver is available in the guest OS
  Completing these tasks correctly prevents the host from interfering with the device and readies it for virtual machine use. This preparation is critical to avoid device conflicts and ensure stable operation in the guest.

Finally, assign the PCIe device to the virtual machine and verify operation in-guest. Use Hyper-V cmdlets like Set-VM or the graphical interface to:

• Map the physical device to the VM
• Start the VM and install any necessary drivers
• Verify the device in the guest using Device Manager or performance tools
  Also consider isolation and performance tuning to minimize latency and maximize throughput. Once verified, the VM can leverage the device as if it were directly attached hardware.

Conclusion

In this section, we've covered how to configure both host and guest for Discrete Device Assignment. You learned to evaluate hardware compatibility, prepare devices by dismounting and marking them assignable, and assign them to virtual machines using Hyper-V tools. Key steps included using PowerShell cmdlets, ensuring proper driver support in the guest, and verifying functionality to maintain isolation and optimize performance. With these practices, you can give VMs direct access to physical PCIe devices for demanding workloads.