Actually WSL2 might be a better target as it would enable some tweaking of the mapping. Did anyone have success implementing virtio communication through hyperv and mount e.g. a custom p9fs. E.g. to support ownership and attributes. What would be the best p9fs server to start with? I had limited success with p9fs on winfsp from cygwin some time ago due to the problems of mapping effective access rights correctly.

I found https://github.com/pfpacket/rust-9p to be reasonably good and easy to hack on. My fork (https://github.com/piscisaureus/rust-9p) has some patches to improve support for the 9P2000.W dialect used by Windows.

Why wouldn't you want to use the VirtualBox guest additions? It's GPLv2 licensed and brings additional features that make using the VM easier.

It's an absolute disaster for one. I haven't actually managed to get shared folders to work reliably in years. It ended up being faster and more reliable to run Samba on the host and connect over a virtual network.

Some of the other features of course can't easily be duplicated with other tools and they work decent-ish anyways so there's no reason to try, but shared folders aren't one of them.

They are always rock solid for me on Windows guests. Linux guests are a different matter altogether, but mainly due to permissions.

You might not want to be locked in. I've used VirtualBox to build systems meant to eventually run elsewhere.