I am using disk passhtru using -scsi but the SMART values can't be access from the VM. Any tricks I am missing to get this to work, or does it not work at all?
SMART doesn't work on a virtual disk, which is what you get when you pass in a disk that way. To use SMART you need to pass in the whole controller as a PCI device. Often you can't do that because it would disable PVE's disks.