[coreboot] what are requirements for coreboot IOMMU support?

[ludphaeus]

Hi
I am trying to port a Haswell laptop and I would want it to have IOMMU support. My chipset supports VT-d but CPU does not. The official info from Intel says the PC needs chipset, CPU and BIOS to support VT-d to use IOMMU. I think this is not true because I saw some boards in board status have working IOMMU with no VT-d support in chipset but with coreboot advertising DMAR table to OS and CPU with VT-d support. Sapphire H61 is a example of this. But other H61 coreboot boards such as P8H61-M LX that have CPU without VT-d advertise no IOMMU capability. So what is really required for full IOMMU ? Do I have chance for full, working IOMMU on this laptop?
Thanks,
Lud