PCIe switches often allow peer-to-peer traffic between downstream ports without going through the IOMMU. This breaks isolation. For true remapping and passthrough, the PCIe topology must support to force all traffic up to the root complex where the IOMMU resides. Without ACS, devices behind a switch can see each other’s memory—a major security flaw.
Now go forth, remap your devices, and virtualize without compromise. pcie device remapping
And so, the lanes were clear, the latency was low, and Leo lived happily (and quickly) ever after. remap your devices