OpenNebula

More info:

root@concertato:~# qemu-system-x86_64 --version
QEMU emulator version 2.2.0 (Debian 1:2.2+dfsg-5expubuntu9.5), Copyright (c) 2003-2008 Fabrice Bellard

root@concertato:~# libvirtd --version
libvirtd (libvirt) 1.2.12

root@concertato:~# qemu-img --version
qemu-img version 2.2.0, Copyright (c) 2004-2008 Fabrice Bellard

Results:

1. Using "file" command and I figured that the template from Marketplace is on QCOW v2, and I think that's what causing the magic block invalid. Using qemu-img to convert the template to compact=1.1(QCOW v3) solves the "image magic is incorrect" error.
2. However it introduces another error when using QCOW v3 to suspend/restore. libvirtd crashed with segfault when trying to "restore" for some reason. "checkpoint" is there however "checkpoint.xml" is empty. Therefore changing the "restore" in the KVM driver to NOT generate a XML solved the problem.

Please look into this issue.

Using these options in modprobe solved the libvirtd crashing issue:

options kvm_intel nested=0
options kvm_intel emulate_invalid_guest_state=0
options kvm ignore_msrs=1

I think my CPU is too restrictive on mem access...