Re: [Xen-devel] Darwin OS (Newbie)

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> Can anyone give me any pointers on modifying Darwin OS  so that it runs on
> top of Xen? My initial assumption is that is would be very much like BSD
> and that I could use BSD as a template.

Bits of it are taken from FreeBSD 5, other bits come from elsewhere: in 
particular you'd certainly also need to make Mach aware of Xen.  There's some 
other stuff in there (e.g. IOKit - Apple's driver framework) - Darwin is 
rather a mutant.

I don't know if Darwin can support BSD-style device drivers (in which case you 
could pretty closely follow the existing BSD drivers) or if you'd have to 
port to IOKit straight away.

One of the first steps in an OS port is obviously to get the initialisation 
code working.  You'll find it helpful to look at the MiniOS code (and the 
initialisation code in the existing ports), that'll give you a good idea of 
the changes that need to be made (e.g. guest starts in protected mode with 
paging enabled and a set of bootstrap page tables).  (side note: the MiniOS 
occasionally breaks due to Xen API changes - I don't know if it works on 
unstable at the moment)

There's also an interface manual in the docs directory but we're awful about 
keeping it up to date ;-)

Cheers,
Mark

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