Comment #4 on issue 161 by [email protected]: Wrong calculation of free memory using xen-pvm (2.4.2 under Gentoo)
http://code.google.com/p/ganeti/issues/detail?id=161
Yes, in grub.conf xen has been started with dom0_mem=256M and in xend-config.sxp there is (dom0-min-mem 0) and (enable-dom0-ballooning no).
As you suggested xm info does report the same as ganeti (150M free) but it is unclear why since nothing is running (except xend and ganeti)!?
