The Stratix® 10 SmartVID feature complies with PMBus 1.3, which supports 1.8V I/O only. A level shifter is required if you use other PMBus devices such as PMBus 1.2, which support 3.3V I/O. PMBus 1.3 devices comply with the corresponding electrical drive levels as given in the SMBus3.0 specification.
The Stratix 10 PWRMGT_SDA and PWRMGT_SCL signals should be connected to a power device with external pull up resistors to 1.8V. The Ipullup is specified from 100uA and 350uA in the SMBus3.3 specification. The Stratix 10 development kit uses 10-K Ohm pull up resistors to 1.8V.