[Public] > On Wed, Mar 16, 2022 at 02:49:09PM +0000, Robin Murphy wrote: > > > What we want is to make sure the Tunneled PCIe ports get the full > IOMMU > > > protection. In case of the discrete above it is also fine if all the > > > devices behind the PCIe root port get the full IOMMU protection. Note in > > > the integrated all the devices are "siblings". > > > > Ah, OK, I wasn't aware that the NHI isn't even the right thing in the first > > place :( > > > > Is there an easy way to get from the struct tb to a PCI device representing > > the end of its relevant tunnel, or do we have a circular dependency > problem > > where the latter won't appear until we've authorised it (and thus the > IOMMU > > layer won't know about it yet either)? > > The PCIe root ports (and the PCIe downstream ports) are there already > even without "authorization". > > There is a way to figure out the "tunneled" PCIe ports by looking at > certain properties and we do that already actually. The BIOS has the > following under these ports: > > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs > .microsoft.com%2Fen-us%2Fwindows-hardware%2Fdrivers%2Fpci%2Fdsd- > for-pcie-root-ports%23identifying-externally-exposed-pcie-root- > ports&data=04%7C01%7Cmario.limonciello%40amd.com%7C0465d319a > 6684335d9c208da07710e7c%7C3dd8961fe4884e608e11a82d994e183d%7C0%7 > C0%7C637830479402895833%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4w > LjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&am > p;sdata=z6hpYGpj%2B%2BVvz9d6MXiO4N66PUm4zwhOdI%2Br6l3PjhQ%3D > &reserved=0 > > and the ports will have dev->external_facing set to 1. Perhaps looking > at that field helps here? External facing isn't a guarantee from the firmware though. It's something we all expect in practice, but I think it's better to look at the ones that are from the _DSD usb4-host-interface to be safer. Mika, you might not have seen it yet, but I sent a follow up diff in this thread to Robin's patch. If that looks good Robin can submit a v2 (or I'm happy to do so as well as I confirmed it helps my original intent too).
