Windows 10 2004 (May 2020 Update) VM upgrade/boot fails with BSOD Stop Code: SYSTEM THREAD EXCEPTION NOT HANDLED

[bluefirestorm]

Workstation Pro version 15.5.6

Host CPU: i7-4770 (Haswell)

Host OS: Ubuntu 18.04.4 LTS

The guest VM upgrade from 1909 to 2004 consistently failed when it reboots with the same BSOD stop code when the guest was configured with 4 vCPUs.

Upgrade of the Windows 10 VM from 1909 to 2004 only succeeded when the vCPU count was reduced from 4 to 2.

After upgrade was successful, changed back to 4 vCPU (doesn't matter if it was 2-2 or 1-4 config) and the BSOD came up again during bootup of the Windows 10 VM.

Setting to 3 vCPU seems OK but I prefer not use an odd count of vCPU.

If anything I find the same problem exists also with Fusion 11.5.3, macOS Catalina 10.15.5 (with i7-4770HQ Crystal Well) with another Windows 10 2004 VM. This VM was not set to 4 vCPUs but I gave it it a try and see if the same problem exists or not.

[bluefirestorm]

Created a brand new VM with Windows 10 Professional 1909 with 4 vCPUs and upgraded to Windows 10 2004 without problems in the same Ubuntu host. I sort of expected it that this would be the case.

The solution (if you can all it that) was to enable the "Virtualize Intel VT-x/EPT or AMD-V/RVI" and add the Hyper-V feature. Without the Hyper-V feature, simply enabling VT-x in the VM it still crashed with the same BSOD stop code with 4 vCPUs or 6 vCPUs. If the Hyper-V feature is removed, it goes back to the same BSOD stop code during boot when there are 4 vCPUs.

This VM has a long history (started out as a Vista Business physical machine and then upgraded to Windows 7 Professional and then P2V'd and upgraded to Windows 10 in its many iterations and last year had its firmware changed from BIOS to UEFI).

The VM in the Fusion already had Hyper-V enabled in the Windows features and it was able to boot with 4 vCPUs is to check "Enable hypervisor applications in the virtual machine".

The long upgrade history might account for the difference from a "clean" Windows 10 Professional 1909 VM without requiring Hyper-V for 4 or more vCPUs. If anyone out there has a more technical explanation; I am all ears.

[BEBvm]

Had a simliar Problem.
Exported a Win10 20H2 from VSphere to an ovf template. Imported it Back to VMWare Workstation. Machine powered on with bod, only when we change the cpu to 2, everything worked.
Solution for this, was to add hpet0.present = "TRUE" to the VMX File.
After that, the machine booted normally.