Resolved! RPMSG SDB driver: memory being allocated from the A7 is not accessible to the M4.
See debug out for details.CA7 : Forward efd info for buf7 with mFdSdbRpmsg:7 and efd:15CA7 : DBG mmappedData[7]:0xb4d00000CM4 : SDB0_RxCpltCallback: B7Ae8800000L00100000CM4 : treatSDBEvent OK physAddr=0xe8800000 physSize=1048576 mArrayDdrBuffCount=7A...