I'm looking for details of VTD_ACCESS.L4_PAGE_HIT events described in Uncore Performance Monitoring Reference Manual. I am testing PCIe performance of two same Cascade Lake systems using VT-d legacy mode and I found there are some differences of VTD_ACCESS related events(especially VTD_ACCESS.L4_PAGE_HIT) behavior between them. I checked that document but nothing is described on it.
What stands for VTD_ACCESS.L4_PAGE_HIT? I presume "L4_PAGE_HIT" means cache hit of PML4 entry. Is it correct?