I managed to port U-Boot 2025.01 with ACPI enabled to cv181x target, as well as made a custom DSDT (.asl ACPI table).
Don’t ask me why, I’m just having some fun ;D
That was enough to get Windows Boot Manager running and being able to control it over serial connection:
I haven’t been able to go further (for now), but that’s a great start.
In case anyone for some random reason wants to repeat this, you can download this fip.bin and put it on an SD card’s boot partition after you’ve installed Windows on ARM on it (make sure to do that on MBR, not GPT), use bcdboot to create UEFI boot files.
If you want to access advanced boot options (the only thing that works!), use bcdedit command to enable it:
bcdedit /store R:\EFI\Microsoft\Boot\BCD /set {globalsettings} advancedoptions yes
In U-Boot over serial, you can use eficonfig to add Windows Boot Manager and make it first in boot order, then use bootefi bootmgr to actually boot, good luck.
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do you have your ported u-boot source code somewhere on git or similar?
I quickly published the code, I’ll warn you that this code is definitely not production-ready or something, AI was used to help with porting, DSDT is not guaranteed to be fully correct, as well as the code has been modified since above fip-acpi.bin has been compiled, so it’s a little bit different (SPI/DTS were changed since then).
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Don’t worry, I didn’t forget about it, thanks to my friend we managed to get kernel debugger connection working (the main reason is the AI generated ACPI tables were wrong) and now we’re actually getting a normal human-readable BSOD.
We will have native Windows on Milk-V Duo S sometime… 
I ported a new version of U-Boot (latest 2026 main branch!) and my friend reworked ACPI, again.
As well, as I had to get more stable installation of Windows.
And now, Milk-V Duo S technically runs Windows 11 on ARM. 
Just a few bare minimum processes, until it BSOD’s because there’s no driver to access the boot SD card itself.
We might have made a kernel driver for SD card storage.
This allows Milk-V Duo S to actually… Start services, dwm, even Defender, enter windeploy stage! That is an insane progress.
