Are you sure 3.15 is the right kernel to test? This is normally running 3.5.0-39-generic.
jbh@jbh-N56VJ:~$ cat /etc/motd
Welcome to Ubuntu 12.10 (GNU/Linux 3.5.0-39-generic x86_64)
* Documentation: https://help.ubuntu.com/
New release '13.04' available.
Run 'do-release-upgrade' to upgrade to it.
Are you sure 3.15 is the right kernel to test? This is normally running 3.5.0-39-generic.
jbh@jbh-N56VJ:~$ cat /etc/motd
Welcome to Ubuntu 12.10 (GNU/Linux 3.5.0-39-generic x86_64)
* Documentation: https://help.ubuntu.com/ upgrade' to upgrade to it.
New release '13.04' available.
Run 'do-release-