You are the PM of Software development project, Higher Management requested you to complete within 2Months, but you know it can not be,

You can find everything related with project integration management in this article. Project Integration  management is an extensive concept.

The top management will be apprised about the time factor and the quality of the project if time is comprised.

I agree with Lucian's response. 

Additionally, i would highlight the risks and document them. 

i agree with previous answers ... thanks for invition