The virt-alignment-scan tool will scan a kvm guest backed by raw image files (*.img) to check for bad 4K alignment.
gstanden@vmem1:~$ sudo virt-alignment-scan -d oracle651
/dev/sda1 1048576 1024K ok
/dev/sda2 525336576 1024K ok
Error: /dev/sdb: unrecognised disk label
gstanden@vmem1:~$ sudo virt-alignment-scan -d oracle631
/dev/sda1 1048576 1024K ok
/dev/sda2 525336576 1024K ok
Error: /dev/sdb: unrecognised disk label
gstanden@vmem1:~$