> b) IOMMU can solve this problem for me by providing a device-specific > contiguous view of a fragmented physical memory allocation > c) In order to enable IOMMU do the above, I need to allocate DRHDs and > DMARs in BIOS initialization (I build my own BIOS)
Yes. The EDK2 firmware toolkit has all the bits you need in it I think. https://firmware.intel.com/sites/default/files/Intel_WhitePaper_Using_IOMMU_for_DMA_Protection_in_UEFI.pdf isn't quite on the topic you want but it does explain it fairly well in passing. https://software.intel.com/en-us/blogs/2009/03/02/intels-virtualization-for-directed-io-aka-iommu-part-1 is a bit out of date but may help too. > Please, let me know if I am on the right track? Of course I realize that > implementing SGDMA would be the best option, but short of that and blocking > out some physical memory on boot, what are my options? If performance is absolutely critical simply stealing a chunk of memory in the firmware and describing it your device some other way is ugly, but for a custom solution I guess anything goes 8) Alan