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Re: [Xen-users] Getting stuck just before booting Dom0

Hi Bhaskar,

Sorry for the delay in getting back to you.

> I havent logged onto the machine through serial port. I am working on the
> machine directly. Just to grab the xen boot messages i am using serial
> console. I think problem is not with serial console. Because, i am getting
> the same problem even if i dont redirect Xen to serial console. Please find
> the grub configuration i am using to boot it.
> title Fedora (
>         root (hd0,0)
>         kernel /boot/xen.gz- com1=115200,8n1 sync_console
> noapic nolapic
>         module /boot/vmlinuz- ro root=LABEL=/ rhgb quiet
> console=ttyS0 console=tty pnpacpi=off noapic nolapic
>         module /boot/initrd-
> I will try to explain the problem in detail..

Well, for a start you could try getting rid of "rhgb quiet" and see if that 
encourages the kernel to give you any more boot output.

I still think you should try redirecting kernel output directly to the Xen 
console and see if that comes out of the serial line (adding xencons=ttyS to 
your current kernel line should do the trick, I think).

> I am trying to boot Xen on top of a simulator.  I found that there are few
> issues with APIC module of that simulator. Still, Linux is able to boot
> without any issues.  Xen is failing to get ccr value from APIC while
> booting. So, I have hardcoded this value. Now, booting is going through
> without any errors, but it is getting stuck just before booting into Dom0
> as I mentioned in my previous mail.

Hmmmm.  So you're logged into the emulated serial line of the simulator, I 
guess?  What simulator are you using?

I'm not terribly familiar with this code.  Xen sort-of requires an APIC.  
Which is to say, you're really *supposed* to have one if you run Xen.  Early 
versions of Xen didn't *need* one but didn't run as well without.  I don't 
know if it's actually a supported configuration - I doubt anybody tests on 
non-APIC systems, so it's quite possible that it doesn't work :-(

I realise that doesn't help much...  You might want to ask some questions on 
xen-devel, explaining what you're trying to do and see if anybody has hints 
about what might work.


> Thanks,
> Bhaskar
> On 4/2/08, Mark Williamson <mark.williamson@xxxxxxxxxxxx> wrote:
> > Hi there,
> >
> >
> > Did you set console output as synchronous whilst you were trying to debug
> > this?  It shouldn't do this by default...
> >
> > > (XEN) Xen is relinquishing VGA console.
> > >
> > > (XEN) *** Serial input -> DOM0 (type 'CTRL-a' three times to switch
> >
> > input
> >
> > > to Xen).  <<<<<<<<<< Nothing happens after this message
> > >
> > > </logs>
> >
> > What's your configuration here?
> >
> > I assume you've built your own Xen rather than using a distro-provided
> > one?
> > (distros usually arrange for the configuration to Just Work, which makes
> > them
> > the most straightforward option for most people).
> >
> > What versions of Xen / XenLinux are you using?  How did you get them?
> >
> > My guess is that dom0 just isn't sending its console output to the right
> > place - you're probably booting OK, you just can't see it...
> >
> > Are you actually logging into this system using the serial line? 
> > Probably dom0's console is appearing on the physical terminal but not on
> > the serial line :-)
> >
> > Try adding console=xvc0 (or possibly just xvc, I can't remember) to your
> > *Linux* kernel command line in your grub config (adding it to the Xen
> > line won't work!).  I think this should at least get you boot output. 
> > You'll probably need to add "xvc0" to /etc/securetty[s ] and add a line
> > to /etc/inittab if you want this to actually be useful for root login.
> >
> > Alternatively, if you already have a serial line setup for vanilla Linux,
> > try
> > passing "xencons=ttyS" to the Linux kernel command line, which will make
> > the
> > Xen console appear like a serial device (so your existing configuration
> > should work).
> >
> > Cheers,
> > Mark
> >
> > --
> > Push Me Pull You - Distributed SCM tool (
> > http://www.cl.cam.ac.uk/~maw48/pmpu/)

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