What IO standards should I choose for PCIE signals?

This is what I have for a design in the Stratix V, works fine for me (@Gen 1, 2 and 3):

set_instance_assignment -name IO_STANDARD HCSL -to pcie_refclk

set_instance_assignment -name IO_STANDARD "3.3-V LVTTL" -to pcie_perstn

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_rx_0

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_rx_1

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_rx_2

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_rx_3

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_rx_4

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_rx_5

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_rx_6

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_rx_7

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_tx_0

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_tx_1

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_tx_2

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_tx_3

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_tx_4

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_tx_5

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_tx_6

set_instance_assignment -name IO_STANDARD "1.5-V PCML" -to pcie_transciever_tx_7