Xen users - Sep 2013 - xen does not work with amd64 kernel but works with 686

Hello,
I have problems running Xen (from Debian 7, i386 userspace) on Asus P3-AE5 
system (M2V-TVM board) with Athlon 64 3000+ CPU (AM2, 1.8GHz).
In short, Xen is not accessible from amd64 Linux kernels but works fine with 
686 kernels.

Long version:
xen-system-i386 (4.1.4-3+deb7u1) works fine with linux-image-3.2.0-4-686-pae

xen-system-amd64 (4.1.4-3+deb7u1) works fine with linux-image-3.2.0-4-686-pae 
or linux-image-3.10-0.bpo.2-686-pae

The same Xen does NOT work with linux-image-3.2.0-4-amd64 or 
linux-image-3.10-0.bpo.2-amd64. Debian starts fine but the boot process 
stalls with:

[....] Starting Xen daemons: xenfs xenstoredFATAL: Failed to initialize dom0 
state: Inappropriate ioctl for device
INFO: task xenstore-write:2696 blocked for more than 120 seconds.

xm then does not work.

Is this a bug (in Xen, Linux or BIOS?) or a configuration problem (amd64 
kernels with i386 userspace)?

-- 
Ondrej Zary

On Mon, 2013-09-23 at 11:11 +0200, Ondrej Zary wrote:
> Hello,
> I have problems running Xen (from Debian 7, i386 userspace) on Asus P3-AE5 
> system (M2V-TVM board) with Athlon 64 3000+ CPU (AM2, 1.8GHz).
> In short, Xen is not accessible from amd64 Linux kernels but works fine
with
> 686 kernels.
> 
> Long version:
> xen-system-i386 (4.1.4-3+deb7u1) works fine with
linux-image-3.2.0-4-686-pae
> 
> xen-system-amd64 (4.1.4-3+deb7u1) works fine with
linux-image-3.2.0-4-686-pae
> or linux-image-3.10-0.bpo.2-686-pae
> 
> The same Xen does NOT work with linux-image-3.2.0-4-amd64 or 
> linux-image-3.10-0.bpo.2-amd64. Debian starts fine but the boot process 
> stalls with:
> 
> [....] Starting Xen daemons: xenfs xenstoredFATAL: Failed to initialize
dom0
> state: Inappropriate ioctl for device
> INFO: task xenstore-write:2696 blocked for more than 120 seconds.
> 
> xm then does not work.
> 
> Is this a bug (in Xen, Linux or BIOS?) or a configuration problem (amd64 
> kernels with i386 userspace)?
The Xen i386 userspace tools cannot run on a 64-bit kernel+hypervisor
combo.

The working combinations are:

64 bit hyp, 64 bit dom0 kernel, 64 bit dom0 userspace.
64 bit hyp, 32 bit dom0 kernel, 32 bit dom0 userspace.
32 bit hyp, 32 bit dom0 kernel, 32 bit dom0 userspace (but 32 bit hyp
has been removed in Xen 4.2)

Supporting 64 bit hyp, 64 bit dom0 kernel, 32 bit dom0 userspace would
require someone to provide kernel "compat ioctl" patches for the
ioctls
used by the xen tools (e.g. at least the /proc/xen/privcmd ones, perhaps
the /dev/xen/* ones).

Ian.