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Re: [Xen-users] "XENBUS: Device with no driver" errors on Debian

On 16 Jul 2008, at 22:35, Mark Williamson wrote:

On Tuesday 15 July 2008, Ben Firshman wrote:
I understand these kernel versions use paravirt_ops or something. Does
this mean there is no PCI passthrough support? Can these kernels even
run with a 2.6.18 dom0? I have tried upgrading to 2.6.25-2 with no luck.

You don't need a matching domU and dom0 kernel, so the kernel should work.

The paravirt_ops kernel doesn't supported PCI passthrough currently; it only supports unprivileged domU functionality. If it's a paravirt_ops kernel
you're using then you can't pass a PCI device to it.

That explains it! I was running a 2.6.24 dom0 and domU on Ubuntu with PCI passthrough working great, so I guess that wasn't pv_ops. Unfortunately, it was incredibly unstable, and I couldn't get it to run for more than a few days without kernel panics. I have a feeling it wasn't just my configuration - they managed to break the networking in their Xen packages during their 8.04 release and for weeks after, so I don't have great deal of trust in their packages. Is anyone else running Xen on Ubuntu's 2.6.24 packages?

You really need a dom0-capable kernel to successfully control a PCI device. Is there any reason not to just use the same kernel as dom0? Is it a driver
support issue?

Yeah, the TV card drivers I need for MythTV don't compile on 2.6.18. I might try running the Ubuntu 2.6.24 kernel as a domU on the Debian 2.6.18 dom0, but it didn't work last time I tried IIRC.

Is there any stable way of running a recent kernel with PCI passthrough? I'm not really bothered about the dom0 distribution, but I'd like the domUs to be debian.

Can someone fill me in? I can't find any documentation about it
anywhere. The debian package descriptions even fail to mention which
kernels will and won't work as a dom0 - it's a matter of trial and
error for new users it seems!

That's a bit unfortunate. You basically need something that is capable of being a dom0 in order to accept a PCI passthrough. If the domU's kernel is
paravirt_ops then it doesn't meet this requirement.

Does the description given by apt-cache show <pkgname> mention anything about
whether something is paravirt_ops or not?

This package provides the binary image for Linux kernel 2.6.18 on i686 and
 compatible machines.

This package provides the binary image for Linux kernel 2.6.25 on i686 and
 compatible machines.

No documentation is included with the packages either and their wiki is vague and out of date. I'll try and clean up their wiki page for future users if I can.

Thanks for the help!


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