Running Xen inside QEMU

Running Xen inside QEMU

[Martin Dommermuth]

Hi there,

I hope this is the right list to ask this. Sorry, if not.

I am about to create a realtime scheduler for XEN as my diploma
thesis. During development I want to run Xen inside of Qemu.
When I try to boot the last lines I see are:
Freeing unused kernel memory: 196k freed
input: ImExPS/2 Generic Explorer Mouse as /class/input/input1

Then nothing more happens. I see qemu maxing out my cpu. I can still
type and delete chars. 
Any idea what's causing this? Is it stuck in Xen or the Linux kernel?

I am running Qemu 0.9.1-1ubuntu1 on Xubuntu 8.04 (Hardy Heron). Xen
is version 3.2.1 which I compiled myself. Inside Qemu I run Debian
4.0 (Etch).

Thanks for any hints!

MartinD:

Re: Running Xen inside QEMU

[Samuel Thibault]

Martin Dommermuth, le Mon 05 May 2008 12:25:51 +0200, a écrit :
> Hi there,
> 
> I hope this is the right list to ask this. Sorry, if not.
> 
> I am about to create a realtime scheduler for XEN as my diploma
> thesis. During development I want to run Xen inside of Qemu.
> When I try to boot the last lines I see are:
> Freeing unused kernel memory: 196k freed
> input: ImExPS/2 Generic Explorer Mouse as /class/input/input1
> 
> Then nothing more happens. I see qemu maxing out my cpu. I can still
> type and delete chars. 
> Any idea what's causing this? Is it stuck in Xen or the Linux kernel?

These messages come from the Linux kernel, so it's most probably Linux
which somehow got wrong.  Which parameters do you give to it?  You may
want to use the serial console as well (add -serial stdio to the qemu
command line).

Samuel

Re: Running Xen inside QEMU

[Martin Dommermuth]

Hi Samuel,

that was a quick reply! :)

* Samuel Thibault wrote/schrieb:

> These messages come from the Linux kernel, so it's most probably Linux
> which somehow got wrong.  Which parameters do you give to it?  You may
> want to use the serial console as well (add -serial stdio to the qemu
> command line).

I have this in /boot/grub/menu.lst

title           Xen 3.2.1 / Debian GNU/Linux, kernel 2.6.18.8-xen
root            (hd0,0)
kernel          /boot/xen-3.2.1.gz
module          /boot/vmlinuz-2.6.18.8-xen root=/dev/hda1 ro console=tty0
module          /boot/initrd-2.6.18.8-xen.img


I'll try the serial console now. Thanks!

MartinD:

Re: Running Xen inside QEMU

[Robert Kaiser (FH)]

Hi,


Am Montag, 5. May 2008 12:31 schrieb Samuel Thibault:
> Martin Dommermuth, le Mon 05 May 2008 12:25:51 +0200, a écrit :
> > Hi there,
> >
> > I hope this is the right list to ask this. Sorry, if not.
> >
> > I am about to create a realtime scheduler for XEN as my diploma
> > thesis. During development I want to run Xen inside of Qemu.
> > When I try to boot the last lines I see are:
> > Freeing unused kernel memory: 196k freed
> > input: ImExPS/2 Generic Explorer Mouse as /class/input/input1
> >
> > Then nothing more happens. I see qemu maxing out my cpu. I can still
> > type and delete chars.
> > Any idea what's causing this? Is it stuck in Xen or the Linux kernel?
>
> These messages come from the Linux kernel, so it's most probably Linux
> which somehow got wrong.  Which parameters do you give to it?  You may
> want to use the serial console as well (add -serial stdio to the qemu
> command line).
>

I'm using qemu's built-in GDB stub to trace/debug Xen, and I had this problem 
too: The Dom0 Linux crashes/hangs just after the message "Freeing unused 
kernel memory: ...". I was able to get it to work by building both Xen and 
the Linux guest with PAE disabled, i.e. "make dist XEN_TARGET_X86_PAE=n".

This seems a bit strange since qemu supposedly supports PAE, nevertheless, 
disabling it fixed the problem for me :-).

Cheers

Rob
-- 
Robert Kaiser                    http://wwwvs.informatik.fh-wiesbaden.de
Labor für Verteilte Systeme            kaiser@informatik.fh-wiesbaden.de
FH Wiesbaden - University of Applied Sciences     tel: (+49)611-9495-294
Kurt-Schumacher-Ring 18, 65197 Wiesbaden, Germany fax: (+49)611-9495-289 


> Samuel
>
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