Re: Support situation for nestedhvm

[Andrew Cooper <andcooper@xxxxxxxxx>]

On 07/11/2023 7:53 pm, Elliott Mitchell wrote:
> I ran into the nestedhvm via the following path.  I was considering the
> feasibility of shedding tasks from a desktop onto a server running Xen.
> I was looking at `man xl.cfg` and noticed "nestedhvm".
>
> Since one of the tasks the computer handled was running other OSes in
> fully simulated environments, this seemed to be something I was looking
> for.  No where did I ever see anything hinting "This configuration option
> is completely unsupported and risky to use".

This one is explicitly covered in SUPPORT.md, and has had XSAs out
against it in the past for being unexpectedly active when it oughtn't to
have been.

> Things simply started exploding without any warnings.

Things also explode if you try to create a VM with 10x more RAM than you
have, or if you try `./xenwatchdogd --help`, or `xl debug-keys c`, or
many other things. 

The xl manpage probably ought to state explicitly that the option is
experimental, but that the extent of what I'd consider reasonable here.

You can't solve educational matters with technical measures.

~Andrew