Qemu kvm native drive for windows vm with grub installed

Software & Operating Systems VFIO
1

First my machine setup:

  • Dual boot ubuntu 18.04/20.04 and windows 10
  • RX550 and R9 290 (later one is for pass-through)
  • R7 1700X
  • 32GB SSD (ubuntu root and /home)
  • 128GB SSD (windows 10 (/dev/sdb1-4) and swap(/dev/sdb5) )
  • other harddrives…

So my machine broke (File corruption after power loss). I managed to reinstall my ubuntu (updated also during this process from 18.04 to 20.04).
But my installation changed: normally I let my ubuntu install grub separately on the 32GB SSD and link the windows boot loader, found on the 128GB SSD, afterwards. This time I forgot it to do and now my boot loaders are on the same drive: 128GB SSD.
Both systems boot fine, but now the important part:
I want to use my windows 10 system in a vm using the existing 128GB SSD. But when I add the entire drive to the vm only the GNU GRUB shell is visible, no starting of windows. Which was possible before my 32GB SSD corrupted.

I see 2 options:

  1. move my grub install back to the 32GB SSD and reinstall windows bootloader on the 128GB SSD

  2. tell my vm-grub-shell to start windows

on both I have no glue how to do it and much more important how to do research on how to do it.

2

My solution usually is to make small ~1GB file based drive and make EFI partition on it. Then put MS bootloader there pointing to your Windoze install. And then pass this small drive as first along with your 128GB ssd device as second to your VM.

This way you will have independent boot drive in case Windows is trying to do something funky with it. Like overwrite grub on SSD when updating.