Can someone explain to me what this is for? The article explicitly mentions that it is not intended to emulate a machine like bochs/vmware or running windows on linux...

So what is this for? Everyone I talked about this subject or use it to run windows apps on *nix ( osx included ) or to create multiple servers in a single machine. What else a hypervisor can do?

EDIT: for the people pointing me the motivation section... well, that is the section I am quoting in first place.

I did read it, but the guy is awfully vague.

And I never used a hypervisor before anyway, thus you can't assume I will understand random jargon.

From the motivation section:

Too many hypervisor projects out there are either extremely complicated (Xen, KVM, VirtualBox) and/or closed-source (VMware, Hyper-V), as well as heavily focused toward Linux-based development or system. Additionally, most (other than Hyper-V) of them are expressly built for the purpose of enabling the execution of virtual machines, and not the virtualization of a live, running system, in order to perform introspection or other security-related tasks on it.

What exactly falls under the "other security-related tasks" section? The only thing I can think of would be for a privileged application to try and hide things from the OS.

Apart from being able to hide from the OS a hypervisor is also safe from manipulation by the OS and can observe and manipulate anything the OS does.

This opens a few doors: debugging or reverse engineering the OS or kernel modules, sandboxing a system you don't trust, detecting rootkits, protecting your antivirus solution from malware, etc.

You could use it to load an image abd inspect how it behaves maybe ?

There is a comprehensive "motivation" section on the linked page of the project.

Sounds a lot like the underappreciated and only lightly documented OSX "hypervisor.framework"

https://developer.apple.com/library/mac/documentation/Driver...

"Veertu" is a VMware/Parallels competitor that uses this: https://itunes.apple.com/us/app/veertu-native-virtualization...

But as far as I know it doesn't support attaching to USB devices so I'm still stuck with VirtualBox.

Edit: There's also xhyve: https://github.com/mist64/xhyve which is a port of FreeBSD's bhyve.

Docker for OS X is using this, so not really that underappreciated.

Why do you call it "underappreciated"?

Probably because OS X is full of cool tech that seems to be weakly documented, underexposed (in terms of API, like the built-in dictionary) or underutilized (because most developers or users aren't always aware of it.)

I really appreciate that Apple doesn't just keep dropping less used features after just 1 OS release like Microsoft does, but I really wish they overhauled their documentation and improved the discoverability of the cool stuff.

I guess I just consider the hypervisor.framework to be not at all exciting. How long has virtualization been out now? When is container.framework coming? I'd also accept jail.framework.

Of all the cool things to do with virtualization or code isolation, they haven't encouraged (or really even enabled) any of it except via the app store sandbox, which isn't even very useful outside of security concerns. 10 years ago I was emulating distributed software on freebsd, including network delays; it's still a damn hassle to do the same setup on darwin.

> after just 1 OS release like Microsoft

Can you give an example? I always found Windows' backwards compatibility to be stellar, though I haven't developed any desktop apps since the Windows 8 introduction.

I don't remember their exact names, but Vista had some apps that were gone in Windows 7, like the Sidebar (a UX paradigm that Apple continues to make arguably better use of in OS X) and some collaboration thing plus others.

I admit that "after just one release" was a bitter exaggeration, but Silverlight, CardSpace, WPF, PhotoDraw and other tech has been unceremoniously dropped or forgotten by MS after a relatively short time.

Apple is guilty of discontinuing apps too, but at least their OS features and platforms are more resilient. For example the Dashboard is still available even though the Notification Center is supposed to supersede it.

> Sidebar, CardSpace, PhotoDraw

Those are applications. Applications get dropped all the time and usually for good reason IMO

WPF and Silverlight are totally still around. Silverlight is languishing for sure, but for good reason (and largely the same reasons as flash).

What I meant by backwards compatibility was that Microsoft rarely breaks or removes API's, so from a developers perspective they aren't any worse than Apple.

> What I meant by backwards compatibility was that Microsoft rarely breaks or removes API's, so from a developers perspective they aren't any worse than Apple.

It's been ages but I remember being annoyed when they sort of nerfed DirectInput into XInput [1]. The earlier API had way more features for advanced force-feedback and some other features. Why cripple things like that at all?

I think the Vista Sidebar vs. OS X Dashboard is a good example; Apple has kept it around for people who might still prefer it, and the widgets made for it still work, whereas any work that developers had put into making Sidebar (and Sideshow [2]) widgets has been negated by Microsoft. I actually liked the Sidebar.

In each of those cases, Microsoft seems to have crippled or took out features and APIs mostly to force something else on us; XBOX and the Windows 8 Start Screen, respectively.

[1] https://en.wikipedia.org/wiki/DirectInput#DirectInput_vs_XIn...

[2] https://en.wikipedia.org/wiki/Windows_SideShow

Wow. Labour of love? Can't say I've ever had the motivation to delve into writing a hyper visor but for anyone else who is interested what a superb reference!

Any recommended project of the same complexity that works on linux?

Lguest: http://lguest.ozlabs.org. It's in the linux kernel.

Thanks!

One that seems reasonably simple is: https://lwn.net/Articles/578295/

Question: I see "x86 versions of Windows are expressly not supported", but does it allow for executing x86 VMs within the hypervisor?

"to support dynamic hyperjacking and unhyperjacking (that is, virtualizing the host state from within the host)."

What? Hyperjacking is a malicious attack against a hypervisor, right? Why is this a design goal? Am I missing something?

Based on my minimal understanding of what it's doing and it's code; It's turning on virtualization, setting up a minimal environment, and then taking the current OS and "moving" it to the virtualized environment. The purpose of doing this in this case is to show how to do it in a minimal fashion, and give it as a jumping off point to create other projects with. Some things that come to mind is a debugger that can't be detected, an easier way to debug a device driver since you could set the hypervisor to log communications with the device somewhere. Or to reverse engineer software that detects normal debuggers being attached and determine what it's actually doing (this is common in malware research I believe).