Xen devel - Nov 2003 - Some general questions about Xen development

I still have some small questions

1) With the experiment of the developers of Xen, is it possible to evaluate the
cost of porting an existing linux driver under Xen. I quickly look network
driver like 3c59x and it seems that it is possible to use the main part of the
original file. Is it nearly the same for other drivers or is it really specific
to each one?

2) I read that some other tools use a type II VMM which seems to be a
"(micro|nano)kernel" with an hosted OS. The goal is to used some
fonctions of
the hosted OS like the drivers. It allows to run native linux drivers. 
I saw in the TODO list that you would like to move the network and the block
device drivers out of Xen. Do you already have an idea about the impact of
porting a driver from Linux to Xen? In fact, a problem to use Xen (for me) is if
we must rewrite many drivers for Xen...

3) You (Ian I think) told me that there is some people who are interested to
port Xen on IA64 (I think it was people from HP). Do you have some news
concerning this port? I ask that because I am also interested to contribute to
this development so if there is some people working on that it could be nice to
work together.Otherwise I will start the project myself :)

Thanks
Guillaume


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> 1) With the experiment of the developers of Xen, is it possible to evaluate
the
> cost of porting an existing linux driver under Xen. I quickly look network
> driver like 3c59x and it seems that it is possible to use the main part of
the
> original file. Is it nearly the same for other drivers or is it really
specific
> to each one?
Porting network drivers is pretty straightforward, particularly
for decent hardware that supports scatter gather DMA.

SCSI drivers can be more troublesome, depending on how much they
rely on using Linux process features (xen is entirely event driven).
 
> 2) I read that some other tools use a type II VMM which seems to be a
> "(micro|nano)kernel" with an hosted OS. The goal is to used some
fonctions of
> the hosted OS like the drivers. It allows to run native linux drivers. 
> I saw in the TODO list that you would like to move the network and the
block
> device drivers out of Xen. Do you already have an idea about the impact of
> porting a driver from Linux to Xen? In fact, a problem to use Xen (for me)
is if
> we must rewrite many drivers for Xen...
We have plans that will make importing device drivers much
easier, by providing a more complete Linux environment emulation.
> 3) You (Ian I think) told me that there is some people who are interested
to
> port Xen on IA64.
A number of people have suggested various architecture ports, but
to date, i''m not aware of anyone actually having gotten
underway. It''s bound to throw up issues where we need to do a
little bit of Xen refactoring, moving stuff to arch-dep
directories.

A good first start might be an x86_64 port, for which I believe
Keir has a design.

Ian


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Selon Ian Pratt <Ian.Pratt@cl.cam.ac.uk>:
> A good first start might be an x86_64 port, for which I believe
> Keir has a design.
Sure it can be a good first start but I need an IA64 port within the framework
of my professional work. So I think I will directly work on the IA64
architecure. However, I would be interested by seeing the x86_64 design by Keir.
It could give me a good and complete overview about various parts that has to be
designed. So Keir, if you don''t mind... ;)

Thank you
Guillaume


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