[coreboot] what are requirements for coreboot IOMMU support?

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

[coreboot] Re: what are requirements for coreboot IOMMU support?

t.org/cgit/board-status.git/tree/sapphire/pureplatinumh61/4.11-659-gef4fe3e37c/2020-01-01T16_12_32Z/kernel_log.txt) indicates DMAR is fully functional and VT-d groups are created. Thanks Lud > On Tue, Feb 23, 2021 at 2:26 PM ludphaeus via coreboot > coreboot@coreboot.org wrote: > > &g