The only supported way to use the PLL as a PMCD is to instantiate the Virtex-4 PMCD and allow the tools to perform the mapping.
To ensure that the PLL is correctly set-up and operates within the specification, please refer to the PLL Switching Characteristics in the Data Sheet and verify that the CLKIN of the PMCD falls within the Fmin and Fmax of the PLL. You can then apply a valid constraint on the CLKIN of the PMCD so that the DRC can check that the PLL operates within a valid range.
In the ISE Design Suite 13.1, the tools will error outif a PLL is used as a PMCD. The reason for the failure is that the default CLKIN_PERIOD results in an invalid set-up from ISE Design Suite 13.2 onwards. You will see an informational message to this effect, however, you still need to verify that the CLKIN meets the requirements and that the PERIOD constraint is applied.