On Fri, Jul 11, 2025 at 09:40:20AM -0600, Alex Williamson wrote: > Yeah, that might work since it does report itself as a host bridge. > Probably noteworthy that you'd end up catching the Intel host bridge > with this too. Yes, I think the argument holds for Intel too. A device with no way to initiate DMA and no MMIO to target P2P can always be its own group, regardless of type. > Again, it should be perfectly safe to assign things downstream of the > ACS isolated root ports in the MFD to userspace drivers, their egress > DMA is isolated. It would only be ingress from an endpoint that seems > like it cannot exist that would be troublesome. I don't have a good > solution. I don't know what the kernel can do with this, IMHO the PCIE capabilities are simply out of spec. If we want to do my relaxed idea then we could also say that root ports without ACS are assumed to have no possible P2P as well. Jason
