RE: [Xen-users] help unmodified OS compatibility

Petersson, Mats
Wed, 22 Feb 2006 21:42:31 -0000

> -----Original Message-----
> From: xen-users-bounces@lists.xensource.com
> [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of
> Jesús Velazquez
> Sent: 22 February 2006 21:04
> To: xen-users@lists.xensource.com
> Subject: [Xen-users] help unmodified OS compatibility
>
> Hi, I have a question regarding the current unmodified OS
> compatibility using Intel VT technology.
>
> Which are the current unmodified OS supported by Xen 3.0.1?
>
> I have trying to install several OS, among them are Solaris
> 10, FreeBSD 6.0, Windows 2000 Server, Windows NT 4, Suse
> Linux 10, Suse Linux Enterprise Server 9 and none of those
> are enable to boot install, install or boot.
>
> The running unmodified guests using VT are RedHat Enterprise
> Linux 4, Fedora core 4, Windows Xp and Windows 2003
> Professional and the Server version.

That''s probably a pretty close approximation of what has been seriously
tested so far. The difficulty is that each OS has it''s own little
quirks about how they do certain things - for example, Windows executes several
instructions AFTER it''s set bit 0 in CR0, without performing a jump to
the protected mode code-segment, so the code looks like it''s running in
protected mode in CR0, but CS is still using the old "real-mode"
values. This is not how the documentation SAYS you should do things, but it
works...

So, until someone decides to actually figure out WHY the different OS''s
don''t work, and fix whatever needs fixing, they will continue to not
work... Depending on various different factors, this may happen sooner or later
- one of those factors is of course participation and bug reporting, another is
vendor presssure, and user pressure. At the moment, I''d say that
unmodified OS''s are still in it''s infancy, and if something
works, great. If it doesn''t, supply a bug-report [obviously check first
if there is someone else that already complained about the same thing - we
probably don''t need to know more than once if WinNT4 doesn''t
work], but don''t expect it to be changed immediately... ;-)
We''re still struggling to get the basics working well... See more
below.

>
> Anyone have an official supported unmodified OS using VT technology?

Try looking at Xen-devel-list, and there will be a test-report issued about
daily from various people listing what tests they have run. This will indicate
how a particular OS is doing - of course, if what you want to run isn''t
listed, it probably means that it''s not on the priority list. For quite
some time, Intel''s testing showed that they couldn''t boot
WinXP at all - not saying they weren''t trying hard to fix it, and
we''ve (AMD) certainly had situations where we''ve struggled to
figure out what''s broken and/or find the right fix for something not
working. Running unmodified guests is not an easy task - you need to understand
quite a lot about what the guest is trying to do when something goes wrong - and
the programmers that work on various OS kernels are often very clever people,
that can figure out how to do things in many different ways - not all of which
are obvious. Not having the source code in many cases doesn''t help
much...

> When is going to be release Xen 3.0.2 ?

Not sure if there''s been any announcement. Ian said something at Xen
summit about 6-8 weeks between dot-releases, but I''m not sure if this
is a target or an absolute [and it''s obviously no point in releaseing a
dot-release if there''s no valuable changes].

> What about the ACPI support for unmodified Guests?

There is an ACPI region supplied in the guest E820 table, but I''m not
sure what information you''re asking for and whether it''s in
this table or not - ACPI contains a lot of different "things", and
some may be simpler than others to emulate.

And of course, just because there''s an entry in the E820
doesn''t mean that it''s containing useful stuff... In my
system, "dmesg" shows a message saying "ACPI: Unable to locate
RSDP", which is, it appears the "Root System Descriptor Table",
and this would probably be fatal for the ACPI... So I guess there''s
more work to be done here... Do you volunteer?

> Where can I find this kind of information?

This mailing list, as well as Xen-devel will have some information - I
don''t think there''s a single location that contains all of
what you want, unfortunately. Obviously, I''ll be ever so happy if
someone told me that I''m wrong in this case...

--
Mats
>
>
> Thanks.
>
> Jesus
>
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