Re: [Xen-users] Some questions from a novice

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

Hello,

> I am a novice at Xen and I have some questions about it and I will
> deeply appreciate the answer from any of you.

Sure.

> 1. Can Xen be run on CPU that not support Virtualization Technology?
> Because I have a Pentium M CPU that does not support VT.

Yes but you'll only be able to run Xen-aware (paravirtualised) guests.  You 
can't run unmodified OSes such as Windows.

> 2. What is each variety of Xen kernel for? For example kernel-2.6-xen,
> kernel-2.6-xen0 and kernel-2.6-xenU. Which one should be used for the
> host OS? What are the differences between kernel-2.6-xen and
> kernel-2.6-xen0?

2.6-xen0 is a kernel with dom0 functionality compiled in, with a fair number 
of device drivers built into the kernel (if I recall correctly) and not that 
many other driver built as modules.

2.6-xen also has dom0 functionality compiled in and it compiles a much larger 
set of modules to ensure compatibility with more hardware.  This is probably 
a good choice for a dom0 kernel, as it'll support lots of devices by default.

2.6-xenU is a kernel that does not include dom0 functionality, so it can only 
run in an unprivileged domain.  You can use this as the kernel in your guest 
VMs.

You can use a dom0-aware kernel (2.6-xen or 2.6-xen0) in *any* domain, 
including an unprivileged domain.  It is safe to use a dom0-aware kernel in 
an unprivileged domain, it won't be able to do any harm.

A 2.6-xenU build is just slightly smaller because it doesn't include dom0 
functionality - that's the only difference.

> 3. I have to build the customer Xen kernel to support some special
> device, can a newer version, such as 2.6.23.9 used in my system now, of
> linux kernel be used?

Not really, no.

You can't build 2.6.23 from kernel.org to run as a dom0 *at all*, so you won't 
be able to use that to get better device support.  You can run 2.6.23 as a 
domU kernel, although the support is better tested and more complete if you 
use the XenLinux kernel from XenSource, at the moment.

If you use a distro with good Xen support, such as Fedora or CentOS then it 
will include a distro-patched XenLinux kernel with extra driver support, etc.  
Fedora ports the Xen patches to work with newer versions of Linux.  If you 
want a more stable, server OS, then you could try CentOS.  CentOS 5 uses the 
2.6.18 kernel but other drivers are backported to enhance its hardware 
support.

There are other distros that do similar modifications, so you might find you 
have luck with one of those instead.  Fedora and CentOS are just the ones I 
know most about ;-)

Cheers,
Mark

-- 
Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/)

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