Package: xen-hypervisor-4.4-amd64 Version: 4.4.1-9+deb8u3 Debian 8.2 installed on a supermicro H8SGL Board, AMD 6128 with 4x4GB ECC RAM.
When booting the plain kernel (stock Jessie 3.16 or backport 4.1 or 4.3), both memory controllers (mc0 and mc1) appear under /sys/devices/system/edac/mc with two csrow* each as expected. Same happens, when booted with Xen 4.1.4-3+deb7u1. When booted with Xen 4.4.1, only mc1 with two RAM modules is visible, although all 16GB RAM is available in the OS (xl info).