[Info-vax] WHY IS VSI REQUIRING A HYPERVISOR FOR X86 OPENVMS?

[Stephen Hoffman]

On 2020-12-31 22:35:45 +0000, Snowshoe said:

> Is there such a thing as an OS-less VM hypervisor?

Nope.

The question is whether the hypervisor is built on its own pieces and 
parts, or is built with and uses an existing operating system; Linux or 
BSD or Windows or otherwise.

Some hypervisors are "thinner" than others, but all must boot and 
perform I/O and related tasks, which makes the hypervisor an operating 
system.

How much else might be included, varies.

Some hypervisors can abstract and can boot themselves as guests (e.g. 
IBM VM), and some (e.g. HPIVM) cannot. Being able to boot a hypervisor 
as a guest is handy for testing new versions of the hypervisor, among 
other uses.

VMware has been migrating off Linux, per their statements: "VMware has 
been actively working on a multi-year project with the goal of removing 
vmklinux from vSphere, and hopes to accomplish this in an upcoming 
major release."  That from earlier in 2020. What they're migrating to? 
Donno. Could well be custom, or could be based on BSD, or otherwise.

> More specifically, a hypervisor which is its own OS in a way, you boot 
> it directly (not booting Linux/Windoze then starting the hypervisor) 
> and pretty much the only thing you can do once booted is starting 
> virtual machines.

There's less of a difference there than you might think, outside of 
cases where the user is expecting to use both the operating system 
booted directly and natively—say, macOS—and using VMware Fusion or 
Parallels to boot Windows or Linux. Most folks running servers boot to 
the hypervisor, load one or more guests potentially including other or 
newer versions of hypervisors as guests, and don't operate their own 
apps co-resident with but independent from the hypervisor. Folks 
running hypervisors on clients tend to be more of a mixed bag.

> I suspect this is the case but I am not familiar with hypervisors.
> I also suspect that many/most/all are really Linux under the hood.

BSD avoids licensing issues, and there's been a fair amount of work 
going into bhyve. macOS has its own hypervisor framework. Etc.

But for the folks that don't want to use a hypervisor, contact the 
folks at VSI and work with them to ensure your preferred x86-64 
platform is supported for native boot without a hypervisor. Or learn to 
love hypervisors, like many of VSI's customers already do.


-- 
Pure Personal Opinion | HoffmanLabs LLC