Re: Microsoft Open-Sources WSL2

On Mon, 5/19/2025 8:17 PM, Lawrence D'Oliveiro wrote:

Windows Subsystem for Linux (WSL2) is the hacked-up pile of glue code
that lets a Linux kernel run on a Windows installation. Now Microsoft
is open-sourcing (nearly) all of that.
 
<https://www.theverge.com/news/669286/microsoft-windows-subsystem-for-linux-open-source>
 
So, do you think this is a good sign or a bad one, in terms of the
future of WSL2 and Windows itself? I see that the GitHub repo already
has about 1000 open issues ...
 

We don't have any documentation for how it works, so it is hard
to make a comment about "what has been given away". for example,
if I installed a Linux Guest as a Guest of the Inverted Hypervisor,
how would that differ from how a Linux kernel would normally get
to run on W10/W11 ?

Even VirtualBox, does not do its own virtualization any more.
It uses the Hypervisor, and your Guest runs on the Hypervisor,
not as a VirtualBox instance. VirtualBox had to add code, so VirtualBox
would be "allowed" to run on W10/W11. That's why the installer stopped
at one point, and I had to replace VBOX 5 with VBOX 6, just so I would
be allowed to finish a Windows Upgrade run.

The scheme could be made more complicated, by some sort of additional
partitioning story. So if anything, what is going on in WSLg is more
interesting that what is going on in WSL2. You probably won't get open
source for WSLg.

The first Terminal Services rootless windows that I know of, was
on WinXP Mode on Windows 7 which uses a special version of VirtualPC.
VirtualPC had Terminal Services added, and the WinXP image talked
to Terminal Services. If you installed any "ordinary" Guest OSes
on the special version of VirtualPC, there was graphical instability
noted. I even had a Guest crash once, because the instability was
too much at one point. What is done in WSLg, bears some similaries,
but the difference is, there's none of the flashing and blinking
that was going in in WinXP Mode. The WSLg stack is not hardware
accelerated, so it's like a MESA fallback code in some ways. And the
Terminal Services is a layer of gravy on top or something.

But unless we see an updated diagram (it would be *very* complicated),
we won't have confirmation of how any of it works. There is one diagram showing
how an Inverted Hypervisor works, and you then have to use your vivid imagination
to guess how various things (the Sandbox) are shoehorned into the framework.

   Paul