ntb_hw(4)/if_ntb(4) driver synced up to Linux Conrad Meyer cem@FreeBSD.org Jon Mason's NTB wiki Intel NTB whitepaper

ntb_hw(4) is now up to date with the Linux NTB driver as of the work-in-progress 4.4 kernel (and actually, contains some fixes that haven't landed in the mainline Linux tree yet but will land in 4.5). Only Back-to-back ("B2B") configurations are supported at this time. Going forward, newer hardware may only support the B2B configuration. if_ntb(4) is mostly up to date with the Linux NTB netdevice driver. Notably absent is support for changing the MTU at runtime.

EMC / Isilon Storage Division Improving if_ntb(4) to avoid using the entire BAR when very large BAR sizes are configured (e.g. 512 GB). Improving pmap_mapdev(9) to somehow allocate only superpage mappings for large BARs, on platforms that support superpages. (NTB BARs can be as large as 512 GB.)