Messages in this thread |  | | From | Alex Feinman <> | Date | Tue, 21 Aug 2018 16:50:22 -0700 | Subject | Re: Contiguous DMA buffer view for a custom device (Intel/x86) |
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Thanks, this sounds like what I need. However, since this is a custom-purpose system, I am tempted to go with CMA and simply preallocated 200MB on start
On Mon, Aug 20, 2018 at 1:58 PM Alan Cox <gnomes@lxorguk.ukuu.org.uk> wrote: > > > 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 is a bit out of date but may help too.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
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