How to passthrough pci device in crosvm?

[Joe]

Hello Developers,
Now I encounted a problem that is in Ubuntu 20.04,the android trout can't boot occasionally.Here is my host info:

-Linux ubuntu 5.11.0-38-generic #42~20.04.1-Ubuntu SMP Tue Sep 28 20:41:07 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

-8GB RAM
-200G Disk
-8 cores

How to passthrough the pci device to guest in crosvm?
We add the following option in "device/google/cuttlefish/host/libs/vm_manager/crosvm_manager.cpp" but failed,
" crosvm_cmd.AddParameter("--vfio=/sys/bus/pci/devices/0000:02:00.0,iommu=on"); "
Is there anything wrong? Or is there any sample can be referenced?

Thanks.