Intel iGPU passthrough on Hyper-V using Discrete Device Assignment (DDA)

Question

I have a Hyper-V VM (Gen 2) running a Linux distribution and would like to passthrough my intel-iGPU (intel UHD graphics) using DDA.
I have encountered the following error after following the Microsoft-HyperV-DDA-guide :

Dismount-VMHostAssignableDevice : The operation failed.
The device cannot be assigned to a virtual machine as the firmware (BIOS or UEFI) on this host
computer system indicates that the device must remain in contact with the firmware running in 
the host. The device can only be used in the management operating system. You should contact
your OEM to determine if a firmware upgrade is available, or if the PCI Express device can be   
reconfigured to be independent of the host firmware.
At line:1 char:1
+ Dismount-VMHostAssignableDevice -force -LocationPath $location
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     + CategoryInfo          : InvalidArgument: (:) [Dismount-VMHostAssignableDevice], VirtualizationException
     + FullyQualifiedErrorId : InvalidParameter,Microsoft.HyperV.PowerShell.Commands.DismountVMHostAssignableDevice

Below are the commands that I executed:

$vm='Gentoo'
$location='PCIROOT(0)#PCI(0200)'
Set-VM $vm -GuestControlledCacheTypes $true
Set-VM $vm -LowMemoryMappedIoSpace 512MB
Set-VM $vm -HighMemoryMappedIoSpace 3GB
Dismount-VMHostAssignableDevice -force -LocationPath $location

Is there any way the PCI Express device can be reconfigured to be independent of the host firmware ?