Cyclone V Avalon-MM interface for PCIE

We use Cyclone V(5CGXFC5C6F27C7) as native PCIE endpoint.

when we use avalon-mm interface and write data to system memory(Linux x86 platform), but system memory has no data(all zeros). Avalon-MM interface is 64-bits width, burstcount is 8.

is there anyone that can help us?

Thanks in advance