Windows8 error: Hypervisor is not running

As you probably know Windows 8 makes usage of Hyper-V, which works very well. Interestingly, few days ago I have updated my BIOS and coincidently at the same time Windows 8 update has been performed too. Shortly after updates, I have suddenly noticed that I’m not able to start any virtual machine on my box, because of following error:

“hypervisor is not running”

I was trying to find out any related change in BIOS. Unfortunately investigation was not successful at all. Machines which were running for months just stopped.
Then I downloaded sysinternals tool CoreInfo which in its new version v3.05 has support for hypervisor.

By using of this tool you can check if the system supports hyper-v and SLAT at all. Call coreinfo.exe –v and you will get (probably) following:

c:\Temp\Coreinfo>coreinfo -v

Coreinfo v3.05 - Dump information on system CPU and memory topology
Copyright (C) 2008-2012 Mark Russinovich
Sysinternals - www.sysinternals.com

Note: Coreinfo must be executed on a system without a hypervisor running for
accurate results.

Intel(R) Core(TM) i7-2720QM CPU @ 2.20GHz
Intel64 Family 6 Model 42 Stepping 7, GenuineIntel
HYPERVISOR      -       Hypervisor is present
VMX            *       Supports Intel hardware-assisted virtualization
EPT            *       Supports Intel extended page tables (SLAT)

The result above says basically that HYPER-V (HYPERVISOR “-“) and SLAT (SLAT “*” are supported, but hypervisor is not activated.
This helps me to understand that I have a software problem.

My problem is in fact the way how I hosting my machine. As described here, I startup my Windows 8 from VHD. Due some updates BIOS or Windows8 hypervisor was not started even if all was right in BIOS.hypervisor is started when booting form VHD, you have to set hypervisorlaunchtype parameter in bcdedit to AUTO.
Following should fix the problem

bcdedit /set {79ec30c7-8799-11de-becd-c6b9ceffc482} hypervisorlaunchtype auto

where GUID is entry identifier in boot. That means you will have to change it with your one.

Unfortunately not all versions of BCDEDIT.EXE supports this hypervisorlaunchtype. After some digging I found out it is easier to install Visual BCD Edit to specify setup all correctly.

After system shut-down (not restart) and start I executed the core info with following result:

HYPERVISOR      *       Hypervisor is present
VMX             -       Supports Intel hardware-assisted virtualization
EPT             -       Supports Intel extended page tables (SLAT)

HYPERVISOR      *  means that hypervisor is running now :)

Boot record looks now like:

Windows Boot Loader
-------------------
identifier              {current}
device                  vhd=[D:]\VirtualMachines\sharepointwithworkflow.vhd
path                    \Windows\system32\winload.exe
description             SPS with Workflow Manager
locale                  en-US
loadoptions             ENABLE_INTEGRITY_CHECKS
integrityservices       Enable
nointegritychecks       Yes
osdevice               vhd=[D:]\VirtualMachines\sharepointwithworkflow.vhd
systemroot              \Windows
resumeobject            {. . .}
hypervisorlaunchtype    Auto
detecthal               Yes

This post is related to development on Windows 8, Windows Server 2012 and Windows Phone (because of emulator).