You see endless messages in dmesg that look something like this:
[9185884.234147] System RAM resource [mem 0x188000000‐0x18fffffff] cannot be added
[9185884.234154] xen_balloon: reserve_additional_memory: add_memory() failed: ‐17
These messages appear to be harmless. These errors are associated with Xen 4.2.0 and Xen 4.2.1.
There is a dirty hack that seems to fix this; however, Idon't understand how or why it works. I don't normally advocate mysterious hacks to silence error messages (does this actually fix anything or just gag the system's screams for help?). Run the following (this is not persistent across reboots):
cat /sys/devices/system/xen_memory/xen_memory0/info/current_kb > /sys/devices/system/xen_memory/xen_memory0/target_kb