id,summary,reporter,owner,description,type,status,component,version,resolution,keywords,cc,guest,host
18192,Windows 10 x64 VM does not start with more than 8 vCPUs and Hyper-V -> duplicate of #17898,multicoreuser,,"I have a request for a Rendering machine with 56 cores.

VirtualBox does not start an Windows 10 x64 Pro for Workstations guest with more than 8 vCores and Hyper-V enabled.

According to 

https://forums.virtualbox.org/viewtopic.php?t=87445

it is a very well known bug and not limited to Win10 Pro for Workstations soI'm surprised I could not find it here.

The log always Shows the following lines:

00:00:04.614859 GIM: HyperV: Guest indicates a fatal condition! P0=0x1e P1=0xffffffffc0000096 P2=0xfffff80360406fd9 P3=0x0 P4=0x0
00:05:36.462561 GUI: Request to close active machine-window.

Host: Ubuntu 18.04.1 LTS
Guest: Windows 10 Pro for Workstations x64

I also tried to start it with KVM. It works but has a terrible performance.
",defect,closed,VMM,VirtualBox 5.2.22,duplicate,,,Windows,Linux