To work around this issue, try using a number of different implementation strategies (for example, register balancing, retiming, etc.).
If the user logic is being driven by the mmcm_clk domain try inserting an additional BUFG for the user logic to allow Vivado to properly balance the user and MIG domain.
If these violations are still seen please open a Service Request for assistance:http://www.xilinx.com/support/service-portal.html
06/30/2015- Initial Release
07/06/2015 - Updated solution