Access On-Chip memory from NIOS and custom logic

1) You could get the fpga hardware initialise to load your memory block - then you only need a single read interface to the memory block.

2) IIRC qsys can instantiate a memory block with the 'other' port directly exposed (so you can use the simple M9K interface instead of an Avalon master one that gets collapsed down because most of the signals aren't needed).

3) You should be able to link the data with your nios program and then get whatever loads your Nios code to load the data to the correct memeory block. Read up on linker scripts and __attribute__((section("name"))).

If you do write the data from the Nios (directly or indirectly via the bootloader) do make sure the data gets past any data cache.