[Xen-devel] VT-X processors , xen 3.0 , drives and virtualization (in 32 bit environment)

[Ian Brown <ianbrn@xxxxxxxxx>]

Hello,

I had read about the new VT-x intel processors and Xen and I am
a bit confused.

According to Intel:
Intel(r) Virtualization Technology allows platforms to run
multiple operating systems and applications in independent partitions.
(I am not clear about what independent partitions exactly are).

In middle of November 2005 Intel anounced new processors
with Virtualization support:
I am talking about 672 and 662 processors with Intel Virtualization Technology
see for example :
http://www.linuxelectrons.com/article.php/20051114100516891


As far as I know,these processors would start shipping
early in Q1 of 2006 and they are still not availale widely (except
samples,tests,etc).
see:
http://lists.xensource.com/archives/html/xen-users/2005-12/msg00604.html

I have 2 questions:

 1) True to now and the current xen-3.0 version: When running Xen 3.0
 on these VT processors, can we run an unmodified kernel ?
 and in such a case, what about the device drivers - isn't there a
 problem with them ? As I understand, the new VT extensions (of Intel)
 allow unmodified OS to run in different CPU contexts in
 a secured way : but sharing physical hw devices still
 requires adding sw support. Are there intentions from
 Xen project to add such hw drivers layer ? Or is it no problem at all??



I mean , in practical terms , if I will set my bootloader to have the
following entry on a machine with VT-x processor:
 kernel /xen.gz dom0_mem=x
 module /vmlinuz-#version ro root=...
 (and initrd if needed)
whereas vmlinuz-#version is an unmodified kernel of some distro:
will it work with support to block and net devices ? will I be
able to create a new domain based also on unmodified vmlinuz-#version
kernel ?

2) I tried to google for data about performance overhead of running
more than one Linux OS instance on these VT-processors but could not find
much.

Xen has an impressive low performance overhead when
using a patched kernel (about 3% of native).

Is there any official (or non-official) data on the performance of these
processors on VT-x processors ?

--IB

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