> Would it be possible to reorganize UML as a VMI ROM, such that it
> actually runs a regular kernel,
With a solid VMI interface you should be able to run a 'regular' kernel
(that uses VMI) in userspace with the right 'thunking' layer, yes.
> ... and have it work essentially the same as the current design.
It would have to be much simpler than the current design, because the
'regular kernel' would expect to manage its processes' VM which would
have to be done entirely in software (and incur a big performance
penalty). I believe the current UML implementation has a (seriously
complicated) mapping of the UML kernel's processes onto host kernel
processes, for VM performance reasons.
Xen and VMWare don't have this problem because unlike UML's host Linux
kernel, they are set up with the clients' VM in mind and are able to give
out portions of physical memory to be managed by each client through a
lightweight indirection of the low-level registers.
A more likely scenario is that UML continues to use a heavily modified
child kernel. Whether it uses a 'VMI ROM' underneath makes little
difference (just moves bits of the patch around).
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