KVM Hypervisor

[Christopher A. Williams]

On Sun, 2008-07-20 at 09:37 -0400, Tom Horsley wrote:
> On Sun, 20 Jul 2008 08:15:29 -0400
> "Alex Katebi" <alex.katebi at gmail.com> wrote:
> 
> > I like Dell laptops but there is no information regarding hardware assisted
> > virtualization (Hypervisor).
> 
> First, it is important to note that I may be completely wrong :-),
> but I don't think anyone makes chips any longer without the virtual
> support instructions, so odds are good that any machine made in the
> last few months will do all the VM instructions.
> 
> Second, you'll get all the purists upset if you use the term
> "hypervisor" in association with KVM :-). The whole point of KVM
> is that it isn't a hypervisor, it is just regular old linux.

Hunh...??? Saying that KVM is not a hypervisor is needlessly splitting
hairs. Quote from the KVM folks from the Linux Symposium 2007
Proceedings, held June 27-30 in Ottawa, Ontario (Canada):
        
        The Kernel-based Virtual Machine, or kvm, is a new
        Linux subsystem which leverages these virtualization
        extensions to add a virtual machine monitor (or hypervisor)
        capability to Linux.

In other words, by leveraging the Intel VT and AMD/V hardware extensions
available in newer processors, KVM enables Linux to *be* the hypervisor.

If you look closely hypervisor technology and architectures, you'll see
that every stand-alone hypervisor (like VMware ESX/ESXi) is essentially
a mini-OS of sorts. Others, like VMware Workstation, VMware Server, and
VirtualBox, add a hypervisor layer on top of the OS (as opposed to in
the OS).

KVM gives the Linux kernel it's own hypervisor capability while
providing all of the benefits that Linux already has. Thus you get the
capability of a stand-alone hypervisor while getting rid of the need to
write / re-write (or for that matter, learn) a lot of other things that
a separate stand-alone hypervisor would have to have. This is what gives
KVM a significant and interesting advantage in the machine
virtualization field.

Cheers,

Chris


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