libvirt users - Sep 2014 - trying but failing - pass-through scsi/sata

hi everybody

I'd imagine this topic must have been covered, yet I've 
failed to find any really helpful and a solid howto/examples 
of how to pass-through a sata disks.

currently I'm having this in my xml:

     <hostdev mode='subsystem' type='scsi'
managed='no'>
       <source>
         <adapter name='scsi_host4'/>
         <address bus='0' target='0' unit='0'/>
       </source>
       <address type='drive' controller='4' bus='0' 
target='0' unit='0'/>
     </hostdev>

I took it from 
http://libvirt.org/formatdomain.html#elementsHostDevSubsys

yet a Linux guest (SL7) fails to find/detect any disks, if I 
dumpxml I get this:

<device>
<name>block_sdb_OCZ_VERTEX4_OCZ_352C77TZVQF1Y3SX</name>
<path>/sys/devices/pci0000:00/0000:00:1f.2/ata5/host4/target4:0:0/4:0:0:0/block/sdb</path>
   <parent>scsi_4_0_0_0</parent>
   <capability type='storage'>
     <block>/dev/sdb</block>
     <bus>ata</bus>
     <drive_type>disk</drive_type>
     <model>OCZ-VERTEX4</model>
     <vendor>ATA</vendor>
<serial>OCZ-VERTEX4_OCZ-352C77TZVQF1Y3SX</serial>
     <size>128035676160</size>
     <logical_block_size>512</logical_block_size>
     <num_blocks>250069680</num_blocks>
   </capability>
</device>

how do I pass-through sata drives?
any help much appreciated, thanks!