[libvirt-users] invalid argument error when using cache parameter

hi, i tried to add a 'cache' argument to the 'driver' element in my domainxml for qemu/kvm. i tried adding cache="none" as well as "writethrough" and "writeback", but every time i get these errors: libvirtError: internal error process exited while connecting to monitor: char device redirected to /dev/pts/1 qemu: could not open disk image /vms/test.img: Invalid argument the full driver line looks like this: <driver name="qemu" type="raw" cache="none"/> the same domainxml works just fine without the cache parameter. does anyone know what i'm doing wrong? is there some other way to set the default cache policy on qemu/kvm? i didn't see anything in the config file... --igor