[vfio-users] gpus are still within the same iommu group, kernel 4.4.0, i7 6700

[Alex Williamson]

On Thu, Jun 9, 2016 at 3:59 AM, <lucas at herich.net> wrote:

> Hello everyone,
>
> I am running a fresh Ubuntu 16.04 and want to use kvm/qemu to run a
> windows VM with a gpu passthrough, however after patching the kernel both
> gpus are still within the same iommu group 1.
> My system:
> - Intel Core i7 6700
> - Gigabyte GA-Z170X-UD5 TH Intel Z170
> - 1x GeForce GTX 650 Ti (used by the host)
> - 1x GeForce GTX 960 (used by the vm)
>
> I am not so well versed with linux, so I read lots of tutorials and
> howtos. However I am kind of stuck right now and do not even know how to
> verify if I used the correct patches (Alex commented within the first
> patch: "This doesn't fix what lspci shows.").
> Hopefully someone could give me an advice how to proceed from here or if I
> should give up.
>
> That is what I have done:
> * install Ubuntu 16.04 (kernel version 4.4.0)
> * install kvm, quemu and so on
> * let vfio-pci grab the GTX 960 (see [1] and [2])
> * install nvidia driver for the GTX 650 Ti
> * build patched kernel (see [3])
> * start virtual machine manager
> * create a vm with windows 7
> * adding passthrough gpu from slot 2 results in (details see [4]): vfio:
> error, group 1 is not viable, please ensure all devices within the
> iommu_group are bound to their vfio bus driver
>

You're overlooking an important qualifier of the patches you're using, they
only enable isolation of devices downstream of *PCH* root ports.  I don't
see a block diagram of the layout in your motherboard manual, but this is
only going to affect the root ports at address 00:1c.*.  As always on
Intel, you need to use a High End Desktop Processor or Xeon E5 or better
CPU to get isolation of the processor root ports (or use the ACS override
patch that I don't support).  Thanks,

Alex
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