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Issues with PCI passthrough to a PV guest

posted in Hypervisor
Wednesday, March 26 2014, 11:07 AM
Hello everyone!
I'm having troubles passing an ethernet card to a PV guest, the Dom0 and DomU are both 64 bit Ubuntu 13.10 (Linux 3.11.0-18) and I'm using Xen 4.3, I'm trying to assign it with xl commands: xl pci-detach 0 pci's bdf, xl pci-assignable-add pci's bdf, xl pci-attach 1 (DomU, whatever it is listed as) pci's bdf OR adding "pci=['pci'sbdf',permissive=1'] (and iommu=soft) to the DomU's config file. Assigning the device itself goes fine but the DomU either can't see it (if I use Ubuntu 10.04, which I did just to see if another version could have a different mileage) or can't use it. Whatever it does if I actually "use" the device (i.e. connect it to my router, of course it doesn't do anything even if it's actually connected) and later shut the domain down by any means (kill, shutdown, or anything else) the whole system will freeze, without any apparent reason, this includes the Dom0.

Is there anything I'm doing wrong? Anything that is wrong with Xen, the Linux kernel, my computer or anything else?

It might be worth noting that:
The machine is a laptop.
It doesn't have IOMMU but it does have VT-X (although I'm not sure this should matter).
l'm trying to pass a NVidia MCP77 Ethernet controller.
At least one other device gets passed through fine (that is the computer's audio card, which was the first device that popped up when I tried to pick one up to see if I would have the same problems).
Xen-Pciback is loaded after Dom0 has booted using modprobe.

Any help will be much appreciated, and if you need any other data to look at in order to help me please do let me know.

Accepted Answer

Wednesday, March 26 2014, 02:52 PM - #permalink

I recommend taking this question to the xen-users mailing list. I'm guessing that this will take some back-and-forth discussion to get this debugged, and there is a larger crowd of techie folks who hang out on that list who will hopefully guide you through the process.

As a baseline: first make sure that the operating system you are using can use the hardware properly without the hypervisor involved (e.g., try it on another machne running Ubuntu 13.10 or whatever). If the bare metal machine cannot reliably use the hardware, the VM never will. If it works okay on the native box, then engage the xen-users list with your config information and hopefully this can get straightened out.

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