On Wed, Jan 18, 2023 at 11:28:32AM -0700, Alex Williamson wrote: > The VT-d spec[2](8.3.1) has a more elegant solution using a path > described in a device scope, based on a root bus number (not > susceptible to OS renumbering) and a sequence of devfns to uniquely > describe a hierarchy or endpoint, invariant of OS bus renumbering.
That's a good idea, we could describe the hierarchy using only devfns. I think I based VIOT mostly on IORT and device-tree which don't provide that as far as I know, but could have studied DMAR better. One problem is that for virtio-iommu we'd need to update both device-tree and VIOT (and neither are easy to change). But it's worth thinking about because it would solve a problem we currently have, that a virtio-iommu using the virtio-pci transport cannot be placed behind a bridge, including a root port, because the firmware tables cannot refer to it. Thanks, Jean
