[fedora-virt] virtual machine 101??

[Paul Lambert]

Been a virt testor for Fedora for a couple of years and use Fedora on my
laptop.  Though familiar with VM I am not an expert in any way as to how it
actually works.  My question is this;  Does the VM engine emulate OS kernel
calls or does the VM engine actually emulate the guest processor assembly
language calls transforming them into equivalent calls to the host
processor?  How does KVM vs Qemu implement VM?

VMware promotes application VM packages where the user application is
packaged with the guest OS.  This allows each application to reside in its
own OS which allows for on demand maintenance, reboots, etc.  At some point
the difference between the way a VM emulates guest applications becomes
blurry.  How much of a reach is it to have just the guest compiled processor
code that can lay directly on a host processor and execute as a quasi OS?
The basic services of monitor, network, etc. could be spawned for each guest
application but they all are layered on top of the host services just as the
like the guest OS does.

The reason I ask these questions is there are many companies in the control
industry that continue to build their own proprietary hardware that is very
expensive and if you what redundancy it is even more.  Some of these devices
sit on a small basic UNIX like OS, others may actually have a proprietary
OS.  Either way, what effort is required to develop a custom VM engine for
such a system so that these types of applications could be virtualized and
reap all the benefits of VM?

In advance, thanks for you assistance.

Paul
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