When targeting a Kintex-7 device, it might not be possible to place the MMCM in such a way that it can be driven directly by the output from an IBUFDS_GTE2.
The solution is to connect the output from the existing BUFH in the core block level to the MMCM CLKIN1 input instead of using the output from the IBUFDS_GTE2 directly.
In the core_name_block.v/vhd file, change the MMCM CLKIN1 input from:
CLKIN1 => q1_clk0_refclk_i,
CLKIN1 => q1_clk0_refclk_i_bufh,
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