Hello,

Same problem here with the same config...

I'm experiencing the same issue on my Precision T7910 running Windows Server 2016..

Microsoft has released a PowerShell script to assist with assessing a system's ability to support DDA, and it is available here:

https://github.com/MicrosoftDocs/Virtualization-Documentation/blob/live/hyperv-tools/DiscreteDeviceAssignment/SurveyDDA.ps1

When I run this script on my T7910 in an elevated PowerShell window, the result for potentially-assignable devices was:

"BIOS kept control of PCI Express for this device.  Not assignable."

This was true even for PCI devices that I had intentionally disabled within Computer Management on my Hyper-V host, which should have made them available to be assigned to a VM on that host.

From reading on Microsoft's sites, this error appears to be due to BIOS limitations around how VT-d is implemented:

https://blogs.technet.microsoft.com/virtualization/2015/11/20/discrete-device-assignment-machines-and-devices/

...I called Dell regarding this issue this evening, but do not currently have technical support on my T7910. Has anyone opened a ticket requesting this to be addressed? - in theory, the way to play it would be: if a Dell box is supposed to support VT-d, but the VT-d implementation is not fully/properly implementing that functionality, it would be reasonable for a purchaser of the device to request that the BIOS be updated to do so.

Thanks,

   - Nathan

Make sure vt-D is enabled, but also that ASPM (active state power management) is enabled i.e. controlled by the OS.