Setting up Discrete Device Assignment with a GPU


Let’s take a look at setting up Discrete Device Assignment with a GPU. Windows Server 2016 introduces Discrete Device Assignment (DDA). This allows a PCI Express connected device, that supports this, to be connected directly through to a virtual machine.

The idea behind this is to gain extra performance. In our case we’ll use one of the four display adapters in our NVIDIA GROD K1 to assign to a VM via DDA. The 3 other can remain for use with RemoteFX. Perhaps we could even leverage DDA for GPUs that do not support RemoteFX to be used directly by a VM, we’ll see.

As we directly assign the hardware to VM we need to install the drivers for that hardware inside of that VM just like you need to do with real hardware.

I refer you to the starting blog of a series on DDA in Windows 2016:

Here you can get a wealth of extra information. My experimentations with this feature relied heavily on these blogs and MSFT provide GitHub script to query a host for DDA capable devices. That was very educational in regards to finding out the PowerShell we needed to get DDA to work! Please see A 1st look at Discrete Device Assignment in Hyper-V to see the output of this script and how we identified that our NVIDIA GRID K1 card was a DDA capable candidate.


There are some conditions the host system needs to meet to even be able to use DDA. The host needs to support Access Control services which enables pass through of PCI Express devices in a secure manner. The host also need to support SLAT and Intel VT-d2 or AMD I/O MMU. This is dependent on UEFI, which is not a big issue. All my W2K12R2 cluster nodes & member servers run UEFI already anyway. All in all, these requirements are covered by modern hardware. The hardware you buy today for Windows Server 2012 R2 meets those requirements when you buy decent enterprise grade hardware such as the DELL PowerEdge R730 series. That’s the model I had available to test with. Nothing about these requirements is shocking or unusual.

A PCI express device that is used for DDA cannot be used by the host in any way. You’ll see we actually dismount it form the host. It also cannot be shared amongst VMs. It’s used exclusively by the VM it’s assigned to. As you can imagine this is not a scenario for live migration and VM mobility. This is a major difference between DDA and SR-IOV or virtual fibre channel where live migration is supported in very creative, different ways. Now I’m not saying Microsoft will never be able to combine DDA with live migration, but to the best of my knowledge it’s not available today.

The host requirements are also listed here:

  • The processor must have either Intel’s Extended Page Table (EPT) or AMD’s Nested Page Table (NPT).

The chipset must have:

  • Interrupt remapping: Intel’s VT-d with the Interrupt Remapping capability (VT-d2) or any version of AMD I/O Memory Management Unit (I/O MMU).
  • DMA remapping: Intel’s VT-d with Queued Invalidations or any AMD I/O MMU.
  • Access control services (ACS) on PCI Express root ports.
  • The firmware tables must expose the I/O MMU to the Windows hypervisor. Note that this feature might be turned off in the UEFI or BIOS. For instructions, see the hardware documentation or contact your hardware manufacturer.

You get this technology both on premises with Windows Server 2016 as and with virtual machines running Windows Server 2016; Windows 10 (1511 or higher) and Linux distros that support it. It’s also an offering on high end Azure VMs (IAAS). It supports both Generation 1 and generation 2 virtual machines. All be it that generation 2 is X64 bit only, this might be important for certain client VMs. We’ve dumped 32 bit Operating systems over decade ago so to me this is a non-issue.

For this article I used a DELL PowerEdge R730, a NVIIA GRID K1 GPU. Windows Server 2016 TPv4 with CU of March 2016 and Windows 10 Insider Build 14295.

Microsoft supports 2 devices at the moment:

  • GPUs and coprocessors
  • NVMe (Non-Volatile Memory express) SSD controllers

Other devices might work but you’re dependent on the hardware vendor for support. Maybe that’s OK for you, maybe it’s not.

Below I describe the steps to get DDA working. There’s also a rough video out on my Vimeo channel: Discrete Device Assignment with a GPU in Windows 2016 TPv4.

Setting up Discrete Device Assignment with a GPU

Preparing a Hyper-V host with a GPU for Discrete Device Assignment

First of all, you need a Windows Server 2016 Host running Hyper-V. It needs to meet the hardware specifications discussed above, boot form EUFI with VT-d enabled and you need a PCI Express GPU to work with that can be used for discrete device assignment.

It pays to get the most recent GPU driver installed and for our NVIDIA GRID K1 which was 362.13 at the time of writing.


On the host when your installation of the GPU and drivers is OK you’ll see 4 NIVIDIA GRID K1 Display Adapters in device manager.


We create a generation 2 VM for this demo. In case you recuperate a VM that already has a RemoteFX adapter in use, remove it. You want a VM that only has a Microsoft Hyper-V Video Adapter.


In Hyper-V manager I also exclude the NVDIA GRID K1 GPU I’ll configure for DDA from being used by RemoteFX. In this show case that we’ll use the first one.


OK, we’re all set to start with our DDA setup for an NVIDIA GRID K1 GPU!

Assign the PCI Express GPU to the VM

Prepping the GPU and host

As stated above to have a GPU assigned to a VM we must make sure that the host no longer has use of it. We do this by dismounting the display adapter which renders it unavailable to the host. Once that is don we can assign that device to a VM.

Let’s walk through this. Tip: run PoSh or the ISE as an administrator.

We run Get-VMHostAssignableDevice. This return nothing as no devices yet have been made available for DDA.

I now want to find my display adapters

#Grab all the GPUs in the Hyper-V Host

$MyDisplays = Get-PnpDevice | Where-Object {$_.Class -eq “Display”}

$MyDisplays | ft -AutoSize

This returns


As you can see it list all adapters. Let’s limit this to the NVIDIA ones alone.

#We can get all NVIDIA cards in the host by querying for the nvlddmkm

#service which is a NVIDIA kernel mode driver

$MyNVIDIA = Get-PnpDevice | Where-Object {$_.Class -eq “Display”} |

Where-Object {$_.Service -eq “nvlddmkm”}

$MyNVIDIA | ft -AutoSize


If you have multiple type of NVIDIA cared you might also want to filter those out based on the friendly name. In our case with only one GPU this doesn’t filter anything. What we really want to do is excluded any display adapter that has already been dismounted. For that we use the -PresentOnly parameter.

#We actually only need the NVIDIA GRID K1 cards, let’s filter some #more,there might be other NVDIA GPUs.We might already have dismounted #some of those GPU before. For this exercise we want to work with the #ones that are mountedt he paramater -PresentOnly will do just that.

$MyNVidiaGRIDK1 = Get-PnpDevice -PresentOnly| Where-Object {$_.Class -eq “Display”} |

Where-Object {$_.Service -eq “nvlddmkm”} |

Where-Object {$_.FriendlyName -eq “NVIDIA Grid K1”}

$MyNVidiaGRIDK1 | ft -AutoSize

Extra info: When you have already used one of the display adapters for DDA (Status “UnKnown”). Like in the screenshot below.


We can filter out any already unmounted device by using the -PresentOnly parameter. As we could have more NVIDIA adaptors in the host, potentially different models, we’ll filter that out with the FriendlyName so we only get the NVIDIA GRID K1 display adapters.


In the example above you see 3 display adapters as 1 of the 4 on the GPU is already dismounted. The “Unkown” one isn’t returned anymore.

Anyway, when we run

$MyNVidiaGRIDK1 = Get-PnpDevice -PresentOnly| Where-Object {$_.Class -eq “Display”} |

Where-Object {$_.Service -eq “nvlddmkm”} |

Where-Object {$_.FriendlyName -eq “NVIDIA Grid K1”}

$MyNVidiaGRIDK1 | ft -AutoSize

We get an array with the display adapters relevant to us. I’ll use the first (which I excluded form use with RemoteFX). In a zero based array this means I disable that display adapter as follows:

Disable-PnpDevice -InstanceId $MyNVidiaGRIDK1[0].InstanceId -Confirm:$false

Your screen might flicker when you do this. This is actually like disabling it in device manager as you can see when you take a peek at it.clip_image015

When you now run

$MyNVidiaGRIDK1 = Get-PnpDevice -PresentOnly| Where-Object {$_.Class -eq “Display”} |

Where-Object {$_.Service -eq “nvlddmkm”} |

Where-Object {$_.FriendlyName -eq “NVIDIA Grid K1”}

$MyNVidiaGRIDK1 | ft -AutoSize

Again you’ll see


The disabled adapter has error as a status. This is the one we will dismount so that the host no longer has access to it. The array is zero based we grab the data about that display adapter.

#Grab the data (multi string value) for the display adapater

$DataOfGPUToDDismount = Get-PnpDeviceProperty DEVPKEY_Device_LocationPaths -InstanceId $MyNVidiaGRIDK1[0].InstanceId

$DataOfGPUToDDismount | ft -AutoSize


We grab the location path out of that data (it’s the first value, zero based, in the multi string value).

#Grab the location path out of the data (it’s the first value, zero based)

#How do I know: read the MSFT blogs and read the script by MSFT I mentioned earlier.

$locationpath = ($DataOfGPUToDDismount).data[0]

$locationpath | ft -AutoSize


This locationpath is what we need to dismount the display adapter.

#Use this location path to dismount the display adapter

Dismount-VmHostAssignableDevice -locationpath $locationpath -force

Once you dismount a display adapter it becomes available for DDA. When we now run

$MyNVidiaGRIDK1 = Get-PnpDevice -PresentOnly| Where-Object {$_.Class -eq “Display”} |

Where-Object {$_.Service -eq “nvlddmkm”} |

Where-Object {$_.FriendlyName -eq “NVIDIA Grid K1”}

$MyNVidiaGRIDK1 | ft -AutoSize

We get:


As you can see the dismounted display adapter is no longer present in display adapters when filtering with -presentonly. It’s also gone in device manager.


Yes, it’s gone in device manager. There’s only 3 NVIDIA GRID K1 adaptors left. Do note that the device is unmounted and as such unavailable to the host but it is still functional and can be assigned to a VM.That device is still fully functional. The remaining NVIDIA GRID K1 adapters can still be used with RemoteFX for VMs.

It’s not “lost” however. When we adapt our query to find the system devices that have dismounted I the Friendly name we can still get to it (needed to restore the GPU to the host when needed). This means that -PresentOnly for system has a different outcome depending on the class. It’s no longer available in the display class, but it is in the system class.


And we can also see it in System devices node in Device Manager where is labeled as “PCI Express Graphics Processing Unit – Dismounted”.

We now run Get-VMHostAssignableDevice again see that our dismounted adapter has become available to be assigned via DDA.


This means we are ready to assign the display adapter exclusively to our Windows 10 VM.

Assigning a GPU to a VM via DDA

You need to shut down the VM

Change the automatic stop action for the VM to “turn off”


This is mandatory our you can’t assign hardware via DDA. It will throw an error if you forget this.

I also set my VM configuration as described in

I give it up to 4GB of memory as that’s what this NVIDIA model seems to support. According to the blog the GPUs work better (or only work) if you set -GuestControlledCacheTypes to true.

“GPUs tend to work a lot faster if the processor can run in a mode where bits in video memory can be held in the processor’s cache for a while before they are written to memory, waiting for other writes to the same memory. This is called “write-combining.” In general, this isn’t enabled in Hyper-V VMs. If you want your GPU to work, you’ll probably need to enable it”

#Let’s set the memory resources on our generation 2 VM for the GPU

Set-VM RFX-WIN10ENT -GuestControlledCacheTypes $True -LowMemoryMappedIoSpace 2000MB -HighMemoryMappedIoSpace 4000MB

You can query these values with Get-VM RFX-WIN10ENT | fl *

We now assign the display adapter to the VM using that same $locationpath

Add-VMAssignableDevice -LocationPath $locationpath -VMName RFX-WIN10ENT

Boot the VM, login and go to device manager.


We now need to install the device driver for our NVIDIA GRID K1 GPU, basically the one we used on the host.


Once that’s done we can see our NVIDIA GRID K1 in the guest VM. Cool!


You’ll need a restart of the VM in relation to the hardware change. And the result after all that hard work is very nice graphical experience compared to RemoteFX


What you don’t believe it’s using an NVIDIA GPU inside of a VM? Open up perfmon in the guest VM and add counters, you’ll find the NVIDIA GPU one and see you have a GRID K1 in there.


Start some GP intensive process and see those counters rise.


Remove a GPU from the VM & return it to the host.

When you no longer need a GPU for DDA to a VM you can reverse the process to remove it from the VM and return it to the host.

Shut down the VM guest OS that’s currently using the NVIDIA GPU graphics adapter.

In an elevated PowerShell prompt or ISE we grab the locationpath for the dismounted display adapter as follows

$DisMountedDevice = Get-PnpDevice -PresentOnly |

Where-Object {$_.Class -eq “System” -AND $_.FriendlyName -like “PCI Express Graphics Processing Unit – Dismounted”}

$DisMountedDevice | ft -AutoSize


We only have one GPU that’s dismounted so that’s easy. When there are more display adapters unmounted this can be a bit more confusing. Some documentation might be in order to make sure you use the correct one.

We then grab the locationpath for this device, which is at location 0 as is an array with one entry (zero based). So in this case we could even leave out the index.

$LocationPathOfDismountedDA = ($DisMountedDevice[0] | Get-PnpDeviceProperty DEVPKEY_Device_LocationPaths).data[0]



Using that locationpath we remove the DDA GPU from the VM

#Remove the display adapter from the VM.

Remove-VMAssignableDevice -LocationPath $LocationPathOfDismountedDA -VMName RFX-WIN10ENT

We now mount the display adapter on the host using that same locationpath

#Mount the display adapter again.

Mount-VmHostAssignableDevice -locationpath $LocationPathOfDismountedDA

We grab the display adapter that’s now back as disabled under device manager of in an “error” status in the display class of the pnpdevices.

#It will now show up in our query for -presentonly NVIDIA GRIDK1 display adapters

#It status will be “Error” (not “Unknown”)

$MyNVidiaGRIDK1 = Get-PnpDevice -PresentOnly| Where-Object {$_.Class -eq “Display”} |

Where-Object {$_.Service -eq “nvlddmkm”} |

Where-Object {$_.FriendlyName -eq “NVIDIA Grid K1”}

$MyNVidiaGRIDK1 | ft -AutoSize



We grab that first entry to enable the display adapter (or do it in device manager)

#Enable the display adapater

Enable-PnpDevice -InstanceId $MyNVidiaGRIDK1[0].InstanceId -Confirm:$false

The GPU is now back and available to the host. When your run you Get-VMHostAssignableDevice it won’t return this display adapter anymore.

We’ve enabled the display adapter and it’s ready for use by the host or RemoteFX again. Finally, we set the memory resources & configuration for the VM back to its defaults before I start it again (PS: these defaults are what the values are on standard VM without ever having any DDA GPU installed. That’s where I got ‘m)

#Let’s set the memory resources on our VM for the GPU to the defaults

Set-VM RFX-WIN10ENT -GuestControlledCacheTypes $False -LowMemoryMappedIoSpace 256MB -HighMemoryMappedIoSpace 512MB


Now tell me all this wasn’t pure fun!

38 thoughts on “Setting up Discrete Device Assignment with a GPU

  1. “This is mandatory our you can’t assign hardware via DDA. It will throw an error if you forget this”

    Are you actually saying that when DDA is used in a VM any reboot of the Host results in a brute “Power Off” of the VM ? Or can you set this back to shutdown or save after you have assigned the device…?

    • Nope, you cannot do that. It acts as hardware, both in the posivitive way (stellar peformance for certain use cases) and in the negative way (you lose some capabilities you’ve become used to with virtualization). Now do note that this is TPv4 or a v1 implementation. We’ll see where this lands in the future. DDA is only for selecte use cases & needs whee the benefits outweigh the drawback and as it breaks through the virtualization layer as such it is also only for trusted admin scenarios.

  2. Haha, yes, understand. But suppose you add a NMVe this way and then reboot the host while heavy IO is going on… “power Off” -> Really ??? 🙂
    Even it’s real HW, you don’t need to turn off or cut power to a real HW system either… Same goes for SRIOV actually, so just sounds like it’s still in beta-testingstage for that matter… Put differently: DD is totally useless if Power Off will be your only choice @RTM…

    • I would not call that totally useless 🙂 A desktop is not totally useless because it can’t save state when you have a brown out. And you also manage a desktop, for planned events you shut it down. The use case determines what’s most immportant.

  3. Shutdown wasn’t an option. Byebye CAU in VDI environment… Are would you go shutdown each VM manually ? I guess it will get better by the time it RTMs. I reckon MS understands that aswell…

  4. So do you think some of the newer graphics cards that will “support” this type of DDA will be able to expose segments of their hardware? let’s say, an ATI FirePro s7150. It has the capability to serve ~16 users, but today, only one VM can use the entire card.

    • It’s early days yet and I do hope more information both from MSFT and card vendors will become available in the next months.

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  8. I’m super close on this. I have the GPU assigned (a K620), but when I install the drivers and reboot, windows is ‘corrupt’. It won’t boot, and it’s not repairable. I can revert to snapshots pre-driver, but that’s about it. I’ve tried this in a Win 8 VM and a Win 10 VM. Both generation 2.

    • I have not seen that. Some issues with Fast Ring Windows 10 releases such as driver issues / errors but not corruption.

      • I think my issues is due to my video card. I’m testing this with a K620. I’m unclear if the K620 supports Access Control Services. I’m curious, your instructions use the -force flag on the Dismount-VmHostAssignableDevice command. Was the -force required with your GRID card as well? That card would absolutely support Access Control Services, I’m wondering if the -force was included for the card you were using, or for the PCI Express architecture. Thanks again for the article, I’m scrambling to find a card that supports Access Control Services to test further. I’m using the 620 because it does not require 6-pin power (My other Quadro cards do).

        • Hi, I’m still trying to get the details from MSFT/NVIDIA but without the force it doens’t work but throws an error. You can always try that. It’s very unclear what’s exactly supported and what not and I’ve heard (nor read) contradicting statements by the vendors involved. Early days yet.

          The error is:
          The operation failed.
          The manufacturer of this device has not supplied any directives for securing this device while exposing it to a virtual
          machine. The device should only be exposed to trusted virtual machines.
          This device is not supported when passed through to a virtual machine.

  9. Hi, I’m wondering if you have any information or experience with using DDA combined with windows server remoteApps technology. I have set up a generation 2 Windows 10 VM with a NVIDIA Grid K2 assigned to it. Remote desktop sessions work perfectly, however my remoteApp sessions occasionally freeze with a dwm.exe appcrash. I’m wondering if this could be something caused by the discrete device assignment? Are remoteApps stable with DDA?

  10. I’m also used a PowerEdge R730 and a Tesla K80, Everything goes fine following your guide by the letter, until installing the driver on the VM, where I get a Code 12 error “This device cannot find enough free resources that it can use. (Code 12)” in Device Manager (Problem Status : {Conflicting Address Range}
    The specified address range conflicts with the address space.)

    Any ideas what might be causing this, the driver is the latest version, and installed on the host without problems.

      • Same here with the R730 and a Tesla K80. Just finished up the above including installing Cuda and I get the same Code 12 error. Anyone figure out how to clear this error up?

  11. Nice read. I’ve been looking around for articles about using pass through with non-quadro cards, but haven’t been able to find much. Yours is actually the best I’ve read. By that I mean two nvidia retail geforce series cards, one for the host one for a pass through to a VM. From what I’ve read I don’t see anything to stop it working, so long as the guest card is 700 series or above, since the earlier cards don’t have support. Is that a fair assesment?

  12. Hi. I have an error when Dismount-VmHostAssignableDevice: “The current configuration does not allow for OS control of the PCI Express bus. Please check your BIOS or UEFI settings.” What check in BIOS? Or maybe try Uninstall in Device manager?

  13. I assigned a K2 GPU to a VM but now I am not able to boot the VM anymore…

    I will get an error that a device is assigned to the VM and therefore it cannot be booted.

    Cluster of 3x Dell R720 on Windows Server 2016, VM is limited to a single Node which has the K2 card (the other two node don’t have graphics cards yet).

      • It looks like it just won’t work when the VM is marked as high available. When I remove this flag and store it on a local hdd of a cluster node it works.

  14. Tried to add a MVIDIA TESLA M10 (GRID) card (4xGPU) to 4 different VMs. It worked flawlessly but after that I could not get back all the GPUs when I tried to remove it from the VM. After Remove-VMAssignableDevice the GPU disappeared from the VM Device manager but I could not mount it back at the host. When listing it shows the “System PCI Express Graphics Processing Unit – Dismounted” line with the “Unknown” status. GPU disappeared from the VM but cannot be mounted and enabled as of your instructions. GPU disappeared? What could possibly caused this?

  15. This is great work and amazing. I have tried with NVIDIA Quadro K2200 and able to use OpenGL for apps I need.

    One thing I noticed, Desktop Display is attached to Microsoft Hyper V Video and dxdiag shows it as primary video adapter. I am struggling to find a way if HYper V Video could be disabled and VM can be forced to use NVIDIA instead for all Display processing as primary video adapter. Thoughts?

    • Well, my personal take on this it’s not removable and it will function as it does on high end systems with an on board GPU and a specialty GPU. It used the high power one only when needed to save energy – always good, very much so on laptops. But that’s maybe not a primary concern. If your app is not being served by the GPU you want it to be serviced by you can try and dive into the settings in the control panel / software of the card, NVIDIA allows for this. Look if this helps you achieve what you need.

  16. My vm is far from stable with a gpu through dda. (Msi r9 285 Gaming 2Gb). Yes it does work, performance is great, sometimes the vm locks up and gives a gpu driver issue. I dont get errors that get logged, just reboots or black/blue screens. Sometimes the vm crashes and comes online during the connection time of a remote connection. (Uptime reset).

    I dont know if it is a problem with Ryzen. (1600x) 16Gb gigabyte ab350 gaming 3.

    Launching Hwinfo64 within the vm those complete lockup the host and the vms. Outside the vm no problems.

    Still great guide, the only one I could find.

      • I disable ULPS, to prevent the gpu from idleing this morning. Vm did keep online for over 4 hours. But still at somepoint it goes doen. Here alle the error codes of the bluescreens ->
        It seems like a driver issue to me.

  17. when reading “Remove a GPU from the VM & return it to the host.” there is a typo.

    Where-Object {$_.Class -eq “System” -AND $_.FriendlyName -like “PCI Express Graphics Processing Unit – Dismounted”}

    the –, should be –

    I got stuck when trying to return the gpu back to the main os, this helped

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