XPAR_PS7_DMA_NS_DEVICE_ID listed in xparameters.h with memory range but does not operate?

Question

Hello All,
I have a zedboard.  Using vivado I built a zedboard preset project.  I then selected the xilinx example peripheral test project.  When I build and run it all works.  The confusion I am having, being used to working with SDK before (previously worked with virtex-5 FXT device), is that the xparameters.h file lists two processor system (PS) DMA peripherals XPAR_PS7_DMA_NS and XPAR_PS7_DMA_S.  The peripheral test uses the XPAR_PS7_DMA_S.  When I change the DMA test to use the _NS device the test fails.  It appears that all the device driver support code reports no errors, but the DMA just does not operate for the _NS device.  When I pull up the processor side block diagram in Vivado it only shows one DMA unit with 8 channels.
I am very confused why xparameters shows the possibility for two DMA instances, but everywhere else, the documentation and tools only list one as usable.
Is the _NS instance just not usable at all?  If so why does it appear with a memory mapping in xparameters.h?
I would appreciate any help.  The reason I am hunting this so hard, is because I would like to dedicate one DMA instance per ARM core.  If there is only one DMA instance available, this will force me to ask the hardware designers to give me a different DMA peripheral to use - so there will not be conflicts between the cores and the peripheral.
Any help is appreciated.
Thank you.

Answer 1

A FAE got back to me, and indicated that there is only one DMA unit with 8 channels.  The S instance is the secure instance of the DMA block.  The NS is the non-secure instance.  The secure versus non-secure operation has to do with ARM Trustzone technology.  By default only the secure DMA version interrupts are usable, to get non-secure interrupts, it takes more work.