PCIS DMA BAR4 Disable Prefetch

I see that BAR4 (used by PCIS) is prefetchable per this document:
https://github.com/aws/aws-fpga/blob/master/hdk/docs/AWS_Fpga_Pcie_Memory_Map.md

How can I disable prefetching for that BAR, similar to BAR0 and BAR1? I know prefetch is a FPGA DMA core setting - but I think it can be disabled in software?

I am looking into if/how it could be done in XDMA. I am about to try setting MAX_EXTRA_ADJ=0 (no extra adjacent descriptors to prefetch). https://github.com/aws/aws-fpga/blob/7f1e76765766f579d3a767bedf669019d50342f3/sdk/linux_kernel_drivers/xdma/libxdma.h

Any information would be helpful.

Update Apparently for 64b address space BARs (like BAR4) you cannot disable prefetching? Only for 32b address spaces?

Thanks

Edited by: absurdfatalism on Jul 5, 2020 7:26 PM