INACCESSIBLE_BOOT_DEVICE after enabling Hyper-V in Windows 10 on Late-2015 27" 5k iMac

They should be trusted, but they are not the 'full' story. These flags indicate that the CPU does support Virtualization, but the rest of the infrastructure on UEFI Macs does not or may not. Based on my testing, after 2012 models, Hyper-V is unstable and/or does not work.

This post - Re: Enable Hyper-V on MacBook Pro Late 2016 makes bootcamp unusable - claims that it works on an early 2015 MBP, but I have no way to verify or contradict it. If someone else has one of these early 2015 models and can test Hyper-V, it would make things a bit more complicated.

The MacBook Pro (Retina, 13-inch, Mid 2014) - Technical Specifications and MacBook Pro (Retina, 13-inch, Early 2015) - Technical Specifications are almost identical, and yet 2015s only support EFI Boot of Windows, but 2014s allow legacy BIOS installation. I have neither unit to test.

Also, About EFI and SMC firmware updates for Intel-based Mac computers - Apple Support - is now stale by at least 2+ years, as of this writing.

Just throwing this out there, it may or may not shed some more light on this issue. I had an idea of creating a bootable VHD and installing Windows 10 on it and then enabling Hyper-V from within that install of Windows. So essentially no change is done to the bootcamp partition since as far as the new installation of windows is concerned it is working with a new partition (bootable VHD). By doing this I ended up with a triple boot option which is nice in itself, I could boot to the bootcamp windows partition or the new windows instance that is on the VHD (so they should essentially be isolated from each other).

I then enabled Hyper-V in the Windows that is powered by the VHD. What I expected to happen was that I would get to the step where I could select Bootcamp Windows (since it is untouched) and the Windows on the VHD but to my surprise I got the INACCESSIBLE_BOOT_DEVICE error before I got to that step. So my conclusion, although not fully verified is that what ever change the Hyper-V install makes is at the boot level before you even get to actual Windows loading. Is this in any way helpful?, hmm, not sure at the moment. What I'm after is exactly what change the Hyper-V install makes that causes the error, I'm thinking something like comparing the boot parameters before and after, not sure how simple that will be but should provide more info.

VHD is just the disk abstraction, like a Virtual disk used by any of the other popular VM engine on the Mac. Booting it up with Hyper-V still requires it to communicate with the available HW resources. The Hypervisor API calls are still being made to the underlying drivers/firmware exposed to Windows. The BC disk partition is just a permanent disk storage for such settings via the BCD and Registry.

Do you have Windows 10 Pro on your Mac?

I agree, however it is just that I thought I could at least get to the point of choosing which instance of Windows (from the 2) to choose to load but it errors out prior to that, anyway as I said it is probably not any new information or helpful. Correct, I'm using Windows 10 Pro.

Let me try and find a test Mac which is 2015/2016 and do some research.

I can confirm that Hyper-V does not work on the late iMac 2015 5k, however it does not make the "inaccessible boot device" failure - it simply fails to properly start Hyper-V once booted.

Also, I can sadly confirm that Windows 10 becomes unbootable on the new MacBook Pro 13" with Touchbar, once Hyper-V is enabled. It is very very annoying as we are heavy users of Docker, which relies on Hyper-V.

novergaard wrote:

It is very very annoying as we are heavy users of Docker, which relies on Hyper-V.

I suggest looking at Enable Hyper-V on MacBook Pro Late 2016 makes bootcamp unusable .

Was able to recreate the issue.

1. Bootcamp installed W2K10
2. Boot into macOs, select startup disk as Bootcamp
3. Boot into W2K10
4. Updated to last build
5. Activate Hyper-V features
6. Restart
7. Boom!

Are you duplicating the issue, or suggesting installing a Windows Server on a Mac? What is W2K10?

Don't know what W2K10 is regardless it looks like that didn't work either. I've tried Window Server 2012 R2 just as a test and that failed also. In testing this on my own just to see what causes the issue it is due to the following property in the boot record:

If you turn that property off, Windows loads and you can load Hyper-V Manager but it throws an error stating the Hypervisor is off. So it really is directly related to the Hypervisor, maybe that is not new information to some people but to me I had to at least find the setting causing the issue.

What would be interesting now is to find some logs of the internals of the Hypervisor just to get more info. So apparently Hyper-V has a debugging mode, if someone has some time maybe they can review the debugging features of Hyper-V and try them. A quick search found this article which could be a starting point:

http://hvinternals.blogspot.com/2015/10/hyper-v-debugging-for-beginners.html

The entries in Event Viewer would be quicker and easier to look at. Let me see if I can find a 2016 MBP and test.

Hi again all,

In fact, life just got even easier. macOS 10.12.4 re-enables VT-d in EFI, meaning that Hyper-V works again, without needing to do the rEFId stuff I described above.

Regards,

Mark

Thank you for posting this!!!!!

I can confirm it works with 10.12.4 with iMac 27" 5K. Woot!!!!

Thanks. I have a 2016 tbMBP in for testing. I will test it in a day or two.