Re: Port DragonFly to Xen platform

[Chris Turner <c.turner@xxxxxxxxxxxxxxxxxxx>]

Sylvestre Gallon wrote:
> It's not that I am not up to it or that I think that I am not able to
> do it, but I will probably need more help and more mentoring to
> implement a kvm-like subsystem than to port dragonflybsd to xen.

Aggelos Economopoulos wrote:
> What kind of changes would you have to make to our core kernel code for
> Xen support?

Was thinking about this again myself - as someone who has mucked around 
with merging various things into vkernel / from other os's -

(assuming you are new to developing on any of the BSD-like systems or 
similar)

you might simply take a look at what it would take to make either 
possible before you commit to one approach or the other -

I'd suggest first investigating how the dragonfly VKERNEL works (as 
you'll need to be adding a new 'architecture' anyhow - and VKERNEL is a 
good example of a quasi-architecture that is part 'real' (e.g. i386), 
and partially 'virtual' (e.g. vkernel's supporting vmspace) - so it 
would be useful to know for either approach.

After you get some kind of understanding of this, perhaps adding some 
silly little change to get a hang of the build process, etc,

perhaps take a look at the NetBSD Xen implementation (as I'd suspect it 
is the best place to start for a port), to see if this approach still 
makes sense..

In the process you'll be able to see how things might work and decide on 
the best approach / pluses and minuses - one thing I can think of 
offhand is that Xen might need more driver work, whereas something 
native might be able to be 'kludged' around .. with xen, you'll need a 
host platform and also a dragonfly dev system (so two build systems / 
source trees to deal with/learn), whereas dragonfly would be one, etc.

of course there are things in the other direction as well but as noted 
before I am biased :)

other side effect of this is at the end of this, you'll know what you're 
getting into - and also have a dev system in place!

anyhow, good luck with your investigation and look forward to hearing 
about your progress in either case..

- Chris