Use the Bootcamp partition under VirtualBox
From: https://apple.stackexchange.com/questions/220670/run-boot-camp-windows10-partition-inside-virtualbox
First, find which disks are EFI and BOOTCAMP with diskutil list.
diskutil list
diskutil unmount /Volumes/BOOTCAMP
sudo chmod 777 /dev/disk0s1
sudo chmod 777 /dev/disk0s3
sudo VBoxManage internalcommands createrawvmdk -rawdisk /dev/disk0 -filename win10raw.vmdk -partitions 1,3
Uncheck “Enable EFI”, uncheck “Enable VT-x/AMD-V”