Xen users - Nov 2006 - pci passthrough and domU madwifi drivers

Hi list,

The crux of my setup is given in the Subject: field. I''m using Xen
3.0.3 (release) on a VIA Nehemiah chipset with Linux 2.6.16.29 in
both dom0 and domU. Because the documentation on PCI passthrough
is a bit sparse, I''m turning to the mailing list..  hopefully you
guys have some input.

My goal is to set up a system where:

 * 1 domU VM runs at a time.

 * The VM can be checkpointed and restored at minimal cost.

 * The running domU has complete control over an Atheros wifi
   card (ie, virtualization should be /as transparent as possible/
   with respect to this device).

Therefore, I set up pci passthrough for the Atheros device
(worked), compiled some domU madwifi kernel modules (worked),
loaded the modules (worked), and presto everything should be fine
(not quite).

Two problems:

1)  Saving or pausing a VM that has madwifi drivers loaded crashes
    dom0 and domU irrecoverably without dropping a line to log or
    console.

2)  Say I unload the modules, checkpoint, and restore the VM.
    Then, when I attempt to modprobe ath_pci, I see this lovely
    little bit[0]. Modules are loaded, no interfaces seen through
    ifconfig/iwconfig.

Furthermore, I''ve tried rebuilding two versions of the madwifi
driver, in hopes that this was a stability issue. Alas, no luck:
both the stable and experimental branches show the same behaviour.

Any advice is appreciated.. I''ll be dealing with this system a lot
over the next few weeks, and I''m willing to do some digging around
if it''s required.

Finally, I doubt that my approach is the only way.. are there any
alternatives? For instance, is it possible to set up a
''virtual''
wifi interface in domU that could be wired over to a dom0 driver?

Thanks in advance,
Greg

[0] http://pastebin.ca/248075

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On Mon, Nov 13, 2006 at 10:31:05PM -0600, Gregory Smith
wrote:
> Two problems:
> 
> 1)  Saving or pausing a VM that has madwifi drivers loaded crashes
>     dom0 and domU irrecoverably without dropping a line to log or
>     console.
> 
> 2)  Say I unload the modules, checkpoint, and restore the VM.
>     Then, when I attempt to modprobe ath_pci, I see this lovely
>     little bit[0]. Modules are loaded, no interfaces seen through
>     ifconfig/iwconfig.
>
> [0] http://pastebin.ca/248075
So here''s a simpler question: has anyone seen this behavior with
other kernel modules when using pci passthrough?

Greg

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