Hello, I'm seeing the same.
After a fresh boot before starting any guests xl shows: root@tank0:~# xl list 0 Name ID Mem VCPUs State Time(s) Domain-0 0 4096 8 r----- 8.4 I did run "xl mem-set 0 4096" then started an guest. This produced a load of the "xen:balloon: Cannot add additional memory (-17)" messages. xl now shows: root@tank0:~# xl list 0 Name ID Mem VCPUs State Time(s) Domain-0 0 4094 8 r----- 24.4 Runnig "xl mem-set 0 4094" after the guest had started seems to have stopped the messages for the moment. (not running mem-set at this point continued to produce the messages in some frequent irregular intervalls) Xen options are "dom0_mem=4096M,max:4096M" . Dom0 linux kernel options are "mem=4096" . xl.conf got autoballoon="off" . Have a nice day, Andre