On 5/26/2021 1:22 AM, Jason Gunthorpe wrote:

On Wed, May 26, 2021 at 12:56:30AM +0530, Kirti Wankhede wrote:

quoted

2. iommu backed mdev devices for SRIOV where mdev device is created per
VF (mdev device == VF device) then that mdev device has same iommu
protection scope as VF associated to it.

This doesn't require, and certainly shouldn't create, a fake group.

Only the VF's real IOMMU group should be used to model an iommu domain
linked to a VF. Injecting fake groups that are proxies for real groups
only opens the possibility of security problems like David is
concerned with.

I think this security issue should be addressed by letting mdev device 
inherit its parent's iommu_group, i.e. VF's iommu_group here.

Kirti

Max's series approaches this properly by fully linking the struct
pci_device of the VF throughout the entire VFIO scheme, including the
group and container, while still allowing override of various VFIO
operations.

Jason