WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-users

RE: [Xen-users] HVMloader boots cdrom but get a blank screen.

To: "Edward Ing" <inge@xxxxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-users] HVMloader boots cdrom but get a blank screen.
From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
Date: Mon, 18 Dec 2006 17:06:08 +0100
Delivery-date: Mon, 18 Dec 2006 08:12:35 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <1166457043.4570.6.camel@localhost>
List-help: <mailto:xen-users-request@lists.xensource.com?subject=help>
List-id: Xen user discussion <xen-users.lists.xensource.com>
List-post: <mailto:xen-users@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AccivHwhqAJT5kEhQIKVThOhpTDS5gAAEbvQ
Thread-topic: [Xen-users] HVMloader boots cdrom but get a blank screen.
> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Edward Ing
> Sent: 18 December 2006 15:51
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] HVMloader boots cdrom but get a blank screen.
> 
> Hi,
> 
> I am trying to install several OSes using HVMloader/cdrom booting
> method.
> When I look at the console I see that the cdrom boot takes place, very
> quickly, however the domU boots into a blank/black screen when
> installing Ubuntu, Kbuntu. It boots into a console, but I can see that
> there is a boot loader error when booting to a FreeBSD cdrom. 
> Windows XP
> works fine.

Try using a "text-only" boot. I know for a fact that some of the
graphics boot routines use "tricky stuff" like "big real-mode", which
particularly on Intel platforms that don't have "real mode
virtualization" in hardware, it can be tricky to make it work. 

FreeBSD, I think, uses segments with base != 0 in protected mode, which
can also be a cause for problems. 

> 
> I don't think that there is much I can do about this. It is 
> the problem
> of distro boot cdrom. But generally, can anyone explain what is the
> problem with distros that run into this problem.

Generically, I would say that the problem is with either the
load-process (where the initial boot-loader loads the installation
kernel) or with graphical boot routines, depending on how far you get
into the boot/install process. 

The problem here is that the processor starts out in real mode, and
that's the only mode that supports BIOS for the purpose of reading the
disk (CD-ROM or otherwise). Since real-mode is restricted to 1MB of RAM,
it can be hard to fit everything into that limited amount of memory - so
the code-writer will have a few choices::
- switch to protected mode, which means no BIOS -> must have drivers
capable of reading the disk by itself. 

- switching back and forth between real-mode and protected-mode. Not too
bad, except it's a little bit of work to be done each switch, and you
can't (practically) use any code from one side of Prot/Real-mode fence
in the other mode. 

- Use "big-real-mode", which is done by switching to protected mode,
setting up a segment register that is not used by BIOS to access "all"
memory, and return to real mode. 

Unfortunately, if the processor doesn't support real mode
virtualization, then the big-real-mode will be a bit of a problem too,
since the Virtual 8086 mode that the processor is in for HVM "real-mode"
doesn't support certain operations such as going to protected mode and
back again and retaining the segment registers values!

This is of course just a GUESS on what the problem is. 

--
Mats
> 
> I am about to try SUSE.
> 
> 
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users
> 
> 
> 



_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users

<Prev in Thread] Current Thread [Next in Thread>