How does local socket IPC work on a multi CPU system?

There is the Supermicro X10DAi motherboard and the manual is here . On page 1-11 you can see that each CPU has it's own RAM. Let's say program A is offering an API through a local socket /var/run/socketapi. This program is started on CPU 1. Then there is program B connecting to this socket and it's started on CPU 2. When program B writes a command to the socket the kernel normally copies the data from the memory space of program B to that of program A. But because the programs run on different CPUs and the memory is not shared between CPUs there is a problem. How is this solved under recent Linux? Maybe the whole memory of CPU 1 is memory mapped to CPU 2 using the QPI interface shown in the manual? Or perhaps the program IPC won't work and an error occurs? Please provide some reference to Linux source code or documentation.