Mark Lloyd wrote:
[snip]

(Has anyone _tried_ nesting VMs - if only out of curiosity? I would
_imagine_ it makes for a very slow VM.)
[]

I expect it would. That may be something to try someday.


We tried that back in the day.

There are different types of VMs. We had some years
ago, that were instruction translators (ran at 0.1x to 0.01x
of real speed). If you nested those, they ran real real slow.

The VMs today are x86 on x86 with "fallthrough" for
instructions, that run at 0.9x (hardly any performance loss).
Where VMs have to be slow, is in the emulated hardware around
them. Storage doesn't run at full speed. Networks are slower,
Graphics though are faster than the "pixel by pixel" drawing
emulations of the past. At one time, you could see rows of pixels
being drawn, the implementation was so dreadful.

What I don't know, is whether the current generation of
x86 on x86 really like to be nested. If your hosting
software can run without VT-X support, you might try
it that way.

The thrill for me wore off years ago (playing Quake at
1 FPS...).

Paul