How to return DDA device to the host if the VM has been removed?

Question

How to return DDA device to the host if the VM has been removed?

JD 51

I have a device assigned to a VM through DDA a long time ago. This VM was recently removed from the server without returning the device to the host. Now I am unable to do so because the command Remove-VMAssignableDevice requires me to define the VMName, while this VM no longer exists.

The device is now stuck in a weird status such that it cannot be used by anything (neither the host nor other VMs). On the host, I do have a device called "PCI Express Graphics Processing Unit - Dismounted" under system devices, which is expected for a device assigned to a VM.

Any idea on how I can get this device back running would be greatly appreciated!

Limitless Technology 39,916 Reputation points

2022-07-15T14:05:24.203+00:00
Hello

Thank you for your question and reaching out. I can understand you are having issues related to DDA device from VM

Please try to boot VM in Safe mode and see if you are able to get DDA device back.

Please try to Restore the VM from Backup or from Replica

Reference :

https://social.technet.microsoft.com/Forums/en-US/3d20bade-9d66-45a7-86c4-6bc2a5df027d/hyperv-20162019-remove-dda-device-from-vm?forum=winserverhyperv

If the reply is helpful, please Upvote and Accept as answer

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PRAKASH T
JD 51 Reputation points

2022-07-18T10:46:56.723+00:00

Thanks for the answer. Unfortunately, the VM that was assigned a DDA device has already been removed, so I cannot boot the VM in safe mode anymore. This particular VM was used only for testing purposes so we do not have any backup for it either. Will physically removing the device from the server or booting the host server into safe mode potentially work? If it is worth it, I can find time to power the server down and try it.

Accepted answer

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Limitless Technology 39,916 Reputation points

2022-07-15T14:05:24.203+00:00

Hello

Thank you for your question and reaching out. I can understand you are having issues related to DDA device from VM

Please try to boot VM in Safe mode and see if you are able to get DDA device back.

Please try to Restore the VM from Backup or from Replica

Reference :

https://social.technet.microsoft.com/Forums/en-US/3d20bade-9d66-45a7-86c4-6bc2a5df027d/hyperv-20162019-remove-dda-device-from-vm?forum=winserverhyperv

If the reply is helpful, please Upvote and Accept as answer

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

PRAKASH T
JD 51 Reputation points

2022-07-18T10:46:56.723+00:00

Thanks for the answer. Unfortunately, the VM that was assigned a DDA device has already been removed, so I cannot boot the VM in safe mode anymore. This particular VM was used only for testing purposes so we do not have any backup for it either. Will physically removing the device from the server or booting the host server into safe mode potentially work? If it is worth it, I can find time to power the server down and try it.

Answer 1

I don't have any DDA-capable devices to test this with so I can't guarantee any of this.

First, the cmdlets that take a -VMName parameter allow wildcards. So -VMName * should always work.
Second, reviewing the available cmdlets, I can't be certain that you're using the one that you want. It seems like the cmdlets with "VMAssignable" in the name are only applicable when working with specific virtual machines. Since the VM in question is gone, I would think that you'd have to look at the device, not VMs. Maybe give the "VMHostAssignableDevice" cmdlets a look.

PS C:\Windows\system32> Get-Command *assignable*  
  
CommandType     Name                                               Version    Source  
-----------     ----                                               -------    ------  
Cmdlet          Add-VMAssignableDevice                             2.0.0.0    Hyper-V  
Cmdlet          Add-VMHostAssignableDevice                         2.0.0.0    Hyper-V  
Cmdlet          Dismount-VMHostAssignableDevice                    2.0.0.0    Hyper-V  
Cmdlet          Get-VMAssignableDevice                             2.0.0.0    Hyper-V  
Cmdlet          Get-VMHostAssignableDevice                         2.0.0.0    Hyper-V  
Cmdlet          Mount-VMHostAssignableDevice                       2.0.0.0    Hyper-V  
Cmdlet          Remove-VMAssignableDevice                          2.0.0.0    Hyper-V  
Cmdlet          Remove-VMHostAssignableDevice                      2.0.0.0    Hyper-V

JD 51 Reputation points

2022-07-22T01:53:17.907+00:00

Thank you, it works! It turns out that the DDA device is simply dismounted on the host, so executing Mount-VMHostAssignableDevice -LocationPath “enter_location_path_string_here” brings the device back to the host and makes it re-assignable. It is just weird there are no official docs from MS on many of these cmdlets.

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How to return DDA device to the host if the VM has been removed?

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