[Pkg-xen-devel] Bug#649923: [xen-hypervisor-4.0-amd64] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0, 0)

[Jan Wagner]

Package: xen-hypervisor-4.0-amd64
Version: 4.0.1-4
Severity: important
Tags: patch, squeeze

We have several recent hardware systems from IBM which have the following 
problem when booting into hypervisor mode on squeeze (amd64, didn't check 
i386):

[    8.184733] pci 0000:01:00.0: BAR 6: no parent found for of device 
[0xfffe0000-0xffffffff]
[    8.213235] Initramfs unpacking failed: junk in compressed archive
[    8.239565] registering netback
[    8.894295] Kernel panic - not syncing: VFS: Unable to mount root fs on 
unknown-block(0,0)
(XEN) Domain 0 crashed: rebooting machine in 5 seconds.

That happen not on all systems and I wasn't able to trace it down to any 
specific hardware combination, but it seems to occure on about 50% of our IBM 
server hardware systems we ordered in the last weeks. There are systems that 
affected and others are not.

I traced the problem down to xen-hypervisor-4.0-amd64, with a backported xen-
hypervisor-4.1-amd64 the problem is gone. Also the Kernel version doesn't 
matters as 3.1 from testing is also affected.

Bastian recommanded me to use "hg bisect" and the result is:

The first good revision is:
changeset:   22375:426f3a265784
user:        Keir Fraser <keir at xen.org>
date:        Tue Nov 09 11:49:49 2010 +0000
summary:     x86: do away with the boot time low-memory 1:1 mapping

So it seems the fix is included into http://xenbits.xen.org/hg/xen-4.1-
testing.hg/rev/426f3a265784

Do you think you can backport a fix to squeeze as there seems to be lot of 
recent IBM systems affected by the issue?

Many thanks, Jan.
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