Microsoft Confirms WSL To Co-Exist With WSL2, Other Windows Subsystem for Linux Details

[phoronix]

Phoronix: Microsoft Confirms WSL To Co-Exist With WSL2, Other Windows Subsystem for Linux Details

Now that Microsoft's Build conference is over where last week they announced Windows Subsystem for Linux 2 (WSL), they have now posted a FAQ to address other common questions about this new implementation for running Linux binaries on Windows 10...

http://www.phoronix.com/scan.php?page=news_item&px=WSL2-More-Details-FAQ

[tildearrow]

So, after all, WSL2 is just a custom Linux kernel on a virtual machine...

Also, why would WSL2 not work in the presence of any other virtualization solutions? I can run multiple virtualized machines using QEMU fine...

[WLBI]

Just wait some more yeas then it will be called LSW (Linux Subsystem for Windows)
And Linux is the foundation for Windows.
Why? It will save Microsoft a lot of money to maintain their system, the kernel and stuff. It's all about money, not about "fan boy" or prestige.
Don't think so? Did you think about WSL 10 years ago?

[ssokolow]

So, after all, WSL2 is just a custom Linux kernel on a virtual machine...

Also, why would WSL2 not work in the presence of any other virtualization solutions? I can run multiple virtualized machines using QEMU fine...

It has to do with you not being able to run Hyper-V and another virtualization host which depends on the CPU's virtualization extensions at the same time. There's nothing wrong with using WSL2 and another Hyper-V-based virtual machine at the same time or two VirtualBox-based VMs at the same time, but you can't mix them.

(Think of it like GPU drivers. Your GPU can only have one OS driving it at once so, if you want your virtualized Windows to use its native drivers, you need another GPU that you can assign exclusively to it.)

[oiaohm]

Just wait some more yeas then it will be called LSW (Linux Subsystem for Windows)
And Linux is the foundation for Windows.
Why? It will save Microsoft a lot of money to maintain their system, the kernel and stuff. It's all about money, not about "fan boy" or prestige.
Don't think so? Did you think about WSL 10 years ago?

10 years ago I was thinking about colinux. http://www.colinux.org/ what is fairly much like WSL 2 running a real Linux kernel inside windows. This end up not workable with Microsoft signed driver requirements.

WSL1 that was made as an attempt to run Android applications on Windows Phone when Microsoft was losing market share. Of course that was a failure and was recycled on the desktop and has basically been another failure with missing syscalls and syscalls that cannot be implemented. Problem is its now a failure with a userbase jumping up and down wanting it to work. WSL2 is to attempt to make that userbase happier.

Of course the fact WSL2 requires to use hypervisor instructions and colinux did not require hypervisor instructions WSL2 is still inferior to what we had before Microsoft introduced signed drivers as mandatory feature.

[xxmitsu]

Perhaps WSL2 will make it possible to port ROCm to windows..

[Guest]

Also, why would WSL2 not work in the presence of any other virtualization solutions? I can run multiple virtualized machines using QEMU fine...

Running multiple QEMU machines at once doesn't prove anything. The problem is that a hypervisor takes control of the hardware that handles virtualization, and only one hypervisor can do so at a time. If you were to try running virtualbox while you have QEMU VMs running, you'd simply get an error message for the same reason WSL2 can't work while other hypervisors are running.

[kobblestown]

Running multiple QEMU machines at once doesn't prove anything. The problem is that a hypervisor takes control of the hardware that handles virtualization, and only one hypervisor can do so at a time. If you were to try running virtualbox while you have QEMU VMs running, you'd simply get an error message for the same reason WSL2 can't work while other hypervisors are running.

The latest version of VirtualBox supports the latest Hyper-V features found in Windows 10 1809 which allow other VM software to use Hyper-V as the hypervisor. Then you can get the UI and tools from VirtualBox but have the VM run on Hyper-V. Sadly, I wasn't able to make this work despite having everything that's needed. Furthermore, it would probably not allow every VBox features like accelerated 3D in the guest.

Then there's nested virtualization. I don't know if Hyper-V supports it, but that would let one run a Hypervisor within a hypervisor.

Finally, if you have the hardware, I strongly recommend running Windows in a VM with GPU Passthrough if you need the performance. I just managed to make this work on a ThreadRipper system and it's lovely. Then I use Linux's KVM for my other virtual machines. In fact, KVM supports nested virtualization (although I don't remember from which kernel version; I think it was something recent) so you could probably run Windows in a VM and have Hyper-V running there for your WSL2 pleasure.

Yeah, it's turtles all the way down.

[roketscyntist]

This isn't great. Currently I'm using vagrant is WSL to test deployments and boxes in VirtualBox. The prospect of going pure Hyper-V for all my VMs isn't appealing.

[numacross]

Running multiple QEMU machines at once doesn't prove anything. The problem is that a hypervisor takes control of the hardware that handles virtualization, and only one hypervisor can do so at a time. If you were to try running virtualbox while you have QEMU VMs running, you'd simply get an error message for the same reason WSL2 can't work while other hypervisors are running.

That's not entirely true since hypervisors can expose the virtualization extensions to a guest, which then can itself start accelerated VMs. This feature is experimental in KVM, VMware supports it from Workstation version 8 and ESXi 5.0 and Hyper-V since Windows 2016.

The limitation for WSL2 might be artificial to cut down on support cost, because nested virtualization has more strict requirements (usually requiring EPT and shaky support for AMD-v). Or they are reusing the micro VM used for security handling in Enterprise versions of Windows which kind of loses its point from the security perspective when the entire system is running in a hypervisor itself.