PCI Passthrough with Debian Wheezy

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PCI Passthrough with Debian Wheezy

Order of module loading

Following the instructions about Xen_PCI_Passthrough with a Debian Wheezy dom0, I encountered the problem that the module for the device I wanted to pass through (a network card) was loaded from the initramfs before the xen-pciback module was loaded. This made it impossible to pass the device through to a domU.

Blacklisting the module for the device I wanted to pass through didn't help. To work around the problem, I edited /etc/initramfs-tools/initramfs.conf so that not "most" modules were included into the image but only the ones that are required: "MODULES=dep" instead of "MODULES=most". After making this change, you need to update the initrd image.

On a side note, I recommend to use the lastest kernel from Debian backports. It works a lot better for me than older versions.

The point is that you need to make sure to load the xen-pciback module before loading the module for the device you want to pass through. This is probably true regardless of which distribution you're using.


permissive option

In case you need the permissive option for a device:

It can be a good idea to give the permissive option as a kernel parameter to dom0 even when xen-pciback is loaded as a module. At least it doesn't seem to hurt --- it works for me with it given both as kernel option and as module option.