no boot possible with LSI / IBM M1015 passthrough

Dear all,

I have a strange problem.

When booting the virtual machine without passthrough of the PCIe card:

- I can install OmniOS (only some errors concerning UHCI USB or warnings occur)
- I can boot OmniOS

After activating passthrough:

- I can't boot - the same machine reports "No active partition" but it boots from the virtual image, not from the M1015 controller
- If I try to reinstall OmniOS, I get a bootloop (only two errors devi (...) vgatext0, but this seems to be only a warning message)

What I'm doing wrong?

Does anyone have Proxmox with M1015 / LSI controller passthrough and OmniOS running?

Thanks a lot