On Thu, Feb 9, 2017 at 5:09 PM, David Reed <[email protected]> wrote:
> I've successfully been able to get two VMs setup with GPU/USB pass-through > and individually they both work, but I can't run both of them at the same > time. Virt-manager will complain that the other's PCI device (GPU) is > already in use even though they don't share the same GPU. > > I suspect it is because both GPUs have the same IOMMU group that is being > assigned to the vfio driver. I was hoping there would be some way to make > this work as they are both being controlled by vfio. > Sorry, this is working as expected for your hardware. The PCIe root ports do not guarantee upstream routing, allowing the possibility of non-IOMMU translated peer-to-peer between downstream devices. See here for further info http://vfio.blogspot.com/2014/08/iommu-groups-inside-and-out.html Hacks to bypass this isolation are not supported upstream. You can find information about processors supporting isolation on root ports here: http://vfio.blogspot.com/2015/10/intel-processors-with-acs-support.html (it's a bit dated but you can extrapolate from the trend). Thanks, Alex
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