Attempting fall back to NEM: VT-x is not available

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Davidian1024
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Joined: 11. Jan 2022, 20:27

Attempting fall back to NEM: VT-x is not available

Post by Davidian1024 »

I have been unable to get VirtualBox to start a VM without seeing the turtle icon for quite some time.

In the VBox.log I always see this line:
HM: HMR3Init: Attempting fall back to NEM: VT-x is not available

I've tried a number of things that seem to be the typical recommendations:
  • Remove Hyper-V
    Remove WSL2
    bcdedit /set hypervisorlaunchtype off
I wonder if there's a way to tell what's making use ofVT-x and therefore preventing VirtualBox from using it.
scottgus1
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Re: Attempting fall back to NEM: VT-x is not available

Post by scottgus1 »

Davidian1024 wrote:if there's a way to tell what's making use of VT-x and therefore preventing VirtualBox from using it.
Unfortunately, no. There's no VT-x/AMD-V user scanner that we know of. But to the best of our knowledge, only active host Hyper-V causes the error you're seeing.

You found the bcdedit command, good. There's a procedure for using it, and situations which prevent its success, see HMR3Init: Attempting fall back to NEM (Hyper-V is active).
Davidian1024
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Joined: 11. Jan 2022, 20:27

Re: Attempting fall back to NEM: VT-x is not available

Post by Davidian1024 »

I managed to get rid of that annoying turtle. :) For the most part at least.

I'm now getting this message:
HM: HMR3Init: VT-x w/ nested paging and unrestricted guest execution hw support
I assume this is what I've been seeking.

My issue was Credential Guard. Which I had thought I disabled.

This link takes you to where you need to go to get the tool that can disable it:
https://docs.microsoft.com/en-us/window ... iness-tool
That page also has details on how to check if it's running.

Unfortunately, after rebooting my machine and starting my VM again the turtle was back and I see Credential Guard is running again. My guess is that my corporate IT department has something in place to enable it at boot. So for now it looks like I'll be disabling that every day.
mpack
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Re: Attempting fall back to NEM: VT-x is not available

Post by mpack »

Davidian1024 wrote: This link takes you to where you need to go to get the tool that can disable it:
No need, and pointless since you already noted that it doesn't work. Just follow the link that Scott provided. The magic bullet is the "bcdedit /set hypervisorlaunchtype off" command, provided it is followed by a full reboot from power off.
Davidian1024
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Joined: 11. Jan 2022, 20:27

Re: Attempting fall back to NEM: VT-x is not available

Post by Davidian1024 »

mpack wrote:
Davidian1024 wrote: This link takes you to where you need to go to get the tool that can disable it:
No need, and pointless since you already noted that it doesn't work. Just follow the link that Scott provided. The magic bullet is the "bcdedit /set hypervisorlaunchtype off" command, provided it is followed by a full reboot from power off.
No, the magic bullet was not "bcdedit /set hypervisorlaunchtype off" followed by a full reboot from power off. I tried that, several times, it did not work.

The link I shared leads to the specific solution that is now consistently working for me. As long as I run that tool every time I go to shutdown or reboot my machine, the turtle icon is gone, and I have the little CPU icon with the V in the middle. And my VM is running great. Faster and no more crashing.

Also, I can tell it's having an effect because upon reboot I am prompted to opt-out of both CredentialGuard and Virtualization-based security.

If I neglect to run that tool before a reboot or a shutdown, CredentialGuard will be active again the next time the system is running, and the turtle will be back along with the problems it causes me. I assume my IT department has something in place that is re-enabling it.

HMR3Init: Attempting fall back to NEM (Hyper-V is active) <- This is a great resource, drilling into it eventually led me to the tool I mentioned. Unfortunately, there seems to be multiple methods on how to disable CredentialGuard.

This whole situation seems very convoluted.
mpack
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Re: Attempting fall back to NEM: VT-x is not available

Post by mpack »

Davidian1024 wrote: No, the magic bullet was not "bcdedit /set hypervisorlaunchtype off" followed by a full reboot from power off. I tried that, several times, it did not work.
Then your PC is unique. Meanwhile the rest of us who use standard Win10 PCs have a few years of experience with this subject matter, and we know what works. That's why we put it in a FAQ response.
scottgus1
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Re: Attempting fall back to NEM: VT-x is not available

Post by scottgus1 »

Davidian1024 wrote:my corporate IT department
Ah, the one shield to the silver bullet. Previously mentioned in the "Attempting fall back to NEM" tutorial. If IT forces it on, it's good MS gave a way to turn it off per boot. IT will block that soon as they find out you're using it, so ixnay on iscussingday that ooltay with your oworkerscay. :lol:
mpack
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Re: Attempting fall back to NEM: VT-x is not available

Post by mpack »

I think the problem here is that the OP has said that the "bcdedit" trick "does not work". Only we know it works. The problem with that is we have no information about the failure. For example if the bcdedit command was blocked by a group policy setting, then I'd expect an error message to be given. Since there was no mention of an error message I assume that this is not the correct explanation.
Nico282
Posts: 1
Joined: 12. Jun 2022, 23:19

Re: Attempting fall back to NEM: VT-x is not available

Post by Nico282 »

After fighting over one hour with the dreaded green turtle, I found the solution in a different thread. Cross posting here because this thread is one of the first results for the error in Google and may save some time to other users.
InfoSecDr wrote: I have followed all of the instructions explicitly to no avail. Multiple times. I even checked the registry to verify that DeviceGuard is not enabled. However, I did discover one registry setting that is not mentioned in any of the published instructions that was set to enabled.

Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\DeviceGuard\Scenarios\SystemGuard

I set the Enabled REG_DWORD value to 0 and rebooted the machine. Now msinfo32 shows that virtualization-based security is not enabled. I started VirtualBox and the turtle is gone and the V icon is there.
fth0
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Re: Attempting fall back to NEM: VT-x is not available

Post by fth0 »

FWIW, System Guard Secure Launch is the security architecture building upon UEFI Secure Boot.
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