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

[Ben Firshman <ben@xxxxxxxxxxxxxx>]

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?
 linux-image-2.6.18-6-xen-686:
 This package provides the binary image for Linux kernel 2.6.18 on  
i686 and
 compatible machines.

linux-image-2.6.25-2-xen-686:
 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!

Ben


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