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Re: [Xen-devel] Changeset 15035 causes x86-32 to hang

To: Stefan Berger <stefanb@xxxxxxxxxx>
Subject: Re: [Xen-devel] Changeset 15035 causes x86-32 to hang
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Sat, 26 May 2007 06:31:51 +0100
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Thread-topic: [Xen-devel] Changeset 15035 causes x86-32 to hang
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On 26/5/07 00:46, "Stefan Berger" <stefanb@xxxxxxxxxx> wrote:

> This changeset seems to have introduced some general instability. A
> complete hang at boot is the best most reproducible case reported so
> far however. It would be great if you can add some tracing and find
> out what is going on. It may be that the underlying bug is also
> responsible for some issues which are harder to reproduce and track down.

At what point does printk() work? All the way at the entry point of __start_xen()?
I have added some printks there but haven't seen any output to the screen so far. Looking at the assembly part now that's calling __start_xen().

I'd help, but I'll be away for a couple of days starting tomorrow...

If you have a serial line attached then you can output characters as early as you like with just a couple of machine instructions. Outputting to VGA text console is similarly quite easy (just write characters to the text console at 0xb8000). It’s not full printk, but is sufficient to track down how far your boot is getting before crash or hang.

 -- Keir
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