My FreeBSD-current/Xen install notes

Julian Stecklina js at
Sat May 23 01:24:02 UTC 2009

Kip Macy <kmacy at> writes:

> Based on L4Linux, I believe that the amount of work required for
> porting a PV OS is much less than creating a new "personality" for a
> microkernel. That said, isn't a hypervisor really a microkernel with
> device and virtual memory abstraction API?

OS personalities were a promise that was always brought up with
microkernels, but never really delivered. Although, L4Linux could be
seen as "Linux personality" for L4. The nice thing about microkernels is
that they abstract enough of the underlying hardware to be open for a
lot of experimenting. I think this is quite nice for student projects.

On the microkernel vs. hypervisor topic: L4 has a very nice virtual
memory abstraction and you can build device abstraction quite easily on
top of it. If you only want paravirtualization, L4 could have delivered
that years before Xen did. And actually it did: L4Linux exists for quite
some time and I believe that there was also a paper on live migration of
L4Linux instances way before Xen did that. IMHO given some commercial
support (and some foresight), L4 could have been the better Xen.

Julian Stecklina

The day Microsoft makes something that doesn't suck is probably the day
they start making vacuum cleaners - Ernst Jan Plugge

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