You might want to write a description such as 
Hypervisor have to trap and emulate the devices when guest OS want to access to devices.
In this time, we provide virtual devices for guest OSes with handling page fault. 
Our virtual devices works with four parameters as following steps:
1. Reads/Checks the fault address(FIPA) from HPFAR.
- Emulate virtual device, if the address is registered in hypervisor as a virtual device.
- Do not emulate virtual device, if the address is not registered in hypervisor as a virtual device.
2. Reads WNR to find the operation types whether the operation is store or load.
3. Reads value of access_size to find the size of the access attempted by the faulted operation.
4. Reads SRT to find the source/destination register.