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Dai
Asked: 2022-01-20 12:55:10 +0800 CST

Hyper-V stopped working after January 2022's Patch Tuesday (2022-01-11): The operating systems boot loader failed with error 0xC00000BB

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  • I only just noticed this now, but apparently since 2022-01-11 ("Patch Tuesday" in January 2022) my home network's dev-server's Hyper-V hypervisor has been unable to start.

    • The box is a 6 year-old Xeon E3 machine (UEFI of course), running Windows Server 2012 R2 with the Domain Controller and Hyper-V host roles installed.

  • The Hyper-V Event Logs are littered with errors, but those are all second-order consequences of the initial service failure which is reported with this event in the System event log:

    Level: Error
    Source: Hyper-V-Hypervisor
    Event ID: 80

    Hypervisor launch failed; The operating systems boot loader failed with error 0xC00000BB.

    • The raw XML of the Event says that the 0xC00000BB code is an NTSTATUS error code, which apparently means "STATUS_NOT_SUPPORTED" - which doesn't make any sense as Hyper-V was working fine before Patch Tuesday and I'm not aware of Intel pushing-out any processor microcode updates to disable hardware virtualization like some kind of horrible SPECTRE/MELTDOWN-esque mitigation...

  • As it happened right after patch Tuesday, I'm guessing Microsoft botched a Hyper-V patch - and I probably shouldn't be expecting the best quality-control for security patches for 8.5-year-old OS releases...

  • Any ideas?

windows-server-2012-r2

0 Answers

  1. Best Answer

    After a bit more Google-fu, I found this thread on HP Enterprise's public forum and a reply from user MDavidRichard attributes the failure to Microsoft update KB5009586:

    No it's nothing to do with HPE. Just remove the Microsoft update KB5009586 and reboot...

    Good luck!

    Microsoft's page for KB5009586 is now updated with a Known Issue that describes my issue (though without any googleable error-codes, no wonder I didn't find this page earlier):

    After installing this update on a device by using Unified Extensible Firmware Interface (UEFI), virtual machines (VMs) in Hyper-V might not start.

    This issue is resolved in KB5010797.

    However I don't see KB5010797 in Windows Update's available downloads list...

    UPDATE: Ah, derp, the KB5010797 patch is for Windows Server 2012 (not Server 2012 R2) while KB5010794 is for Windows Server 2012 R2.

    TL;DR:

    Install KB5010797 or KB5010794 depending on your OS.

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