Is there a reference example of two M7 cores access shared memory based on shared memory (not through IPCF)?
I am not aware of any example but an example Platform_Multicore_SingleElf_S32K324, but it does not show any shared memory accesses.
S32K3 hardware itself is capable to access all memory resources by all cores. In RTD, this should be configured by RM (Resource Manager) driver consisting of MPUC, XRDC, SEMA42, RAM an FLASH controller, VIRT_VRAPPER, XBIC and XBAR setup. This however will not avoid possible data coherency issues what using IPCF should eliminate, at least I understand it this way.