Re: [Qemu-devel] [questions] about using vfio to assign sr-iov vf to vm

[Alex Williamson]

On Thu, 2014-08-14 at 16:22 +0800, Zhang Haoyu wrote:
> Hi, all
> I'm using VFIO to assign intel 82599 VF to VM, now I encounter a problem,
> 82599 PF and its VFs belong to the same iommu_group, but I only want to 
> assign some VFs to one VM, and some other VFs to another VM, ...,
> so how to only unbind (part of) the VFs but PF?
> I read the kernel doc vfio.txt, I'm not sure should I unbind all of the 
> devices which belong to one iommu_group?
> If so, because PF and its VFs belong to the same iommu_group, if I unbind the 
> PF, its VFs also diappeared.
> I think I misunderstand someting,
> any advises?

This occurs when the PF is installed behind components in the system
that do not support PCIe Access Control Services (ACS).  The IOMMU group
contains both the PF and the VF because upstream transactions can be
re-routed downstream by these non-ACS components before being translated
by the IOMMU.  Please provide 'sudo lspci -vvv', 'lspci -n', and kernel
version and we might be able to give you some advise on how to work
around the problem.  Thanks,

Alex