[kwlug-disc] Microsoft Linux

[Jason Eckert]

No problem :-)

In the WSL2 architecture, both the Windows kernel and the Microsoft version
of the Linux kernel are run simultaneously on top of Hyper-V (ring 0).

The Win10 host OS kernel maintains a close (non-separable) integration with
Hyper-V, while guest operating systems (which run at the same
privilege level) do not, regardless of whether they are running
Win10/WinServer/Linux/FreeBSD. This also means that the Win10 host can
theoretically cause issues with Hyper-V and vice versa (there was a CVE
surrounding that earlier in 2019 I recall, but it was one where it was too
difficult for someone to take advantage of practically).

Thus, the host OS is tied to ring0 in Win10, but guest operating systems
are not and need not be started at all times. Thus, the Microsoft version
of the LInux kernel (which runs in a Hyper-V VM) is only started on demand
when you open that distribution's shell, and stopped when you exit your
last connection. You can use the "wsl" command to see this behaviour.

In Win11 I noticed from the output of "wsl -l -v" that Microsoft version of
the Linux kernel is running all the time (even if no distributions are
installed in WSL2), and started at boot time, which means it is tied to
ring0 like the Win11 host OS.

What I'm curious about is whether this is the case if you upgrade from a
machine that did not have Hyper-V enabled already. If it is, it also means
that the underlying Hyper-V hypervisor is now a core component of Win11
(like KVM), and when you install the Hyper-V feature, you're getting the
tools and extras only.  This makes sense since many programs now require
Hyper-V, such as Visual Studio, and Microsoft continues to add hooks in
their software for it.

Each year, it seems less and less absurd that Microsoft may switch to a
Linux kernel, so you may have inadvertently made an accurate prediction...



On Thu, Aug 12, 2021 at 12:42 PM Paul Nijjar via kwlug-disc <
kwlug-disc at kwlug.org> wrote:

>
> Could you elaborate on this? I know what ring 0 is and I know what a
> Linux kernel is, but I do not know how to find out more about what is
> running in ring 0. Is it some hypervisor?
>
> I misinterpeted this as "Windows is switching to the Linux kernel" and
> now I am profoundly embarrassed.
>
> - Paul
>
> On Thu, Jul 22, 2021 at 01:39:05PM -0400, Jason Eckert wrote:
> > Since Win11 is running a Linux kernel in ring 0 all the time, you could
> > argue that it is, in fact, a Linux distro.
> > It's just a matter of time before Systemd takes over all Windows
> > configuration ;-)
> >
> > On Thu, Jul 22, 2021 at 12:54 PM Charles M <chaslinux at gmail.com> wrote:
> >
> > > Not really surprising given that they've been porting tools since at
> > > least 2016 from what I remember:
> > >
> > > https://www.youtube.com/watch?v=0Gofc7mrnzE
> > >
> > > Not a desktop distribution. But maybe when they get a bunch more tools
> > > together we'll see a desktop distribution from them as well.
> > >
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