PCI Passthrough with Debian Wheezy

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

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.