Use raw disk/partition as VirtualBox disk image

make-vmdk.sh

# verify your disk layout
lsblk -o NAME,FSTYPE,UUID
# NAME   FSTYPE UUID
# sda           
# ├─sda1 ntfs   ECEAA4D4EAA49BF8 <- reserve partition
# ├─sda2 ntfs   9CD2C43CD2C41C80 <- windows 
# ├─sda3        
# ├─sda5 ext4   5f9e05c1-ace9-45ee-a884-ed1df68bdc3e <- /boot partition
# ├─sda6 ext4   bc1a75df-3625-4c1f-b53a-8ecc725f0d23
# └─sda7 btrfs  d305a656-442f-4579-96cf-dadc964c0be2

# copy MBR
dd if=/dev/sda of=Windows.mbr count=1 bs=512
# create raw disk image
# if you have grub installed on MBR, you must include partition contains /boot folder, this case it's sda5
VBoxManage internalcommands createrawvmdk -filename Windows.vmdk -rawdisk /dev/sda -mbr Windows.mbr -partitions 2,5

# That's all, use the created image as normal, and DONT forget to select Windows to boot if you are using grub