Since the emerging of the OpenStack cloud computing platform in the Ubuntu community, increasing number of public/private cloud service providers choose to deploy it all over the world. Recently, Spectre and Meltdown have caused a panic in the world and the Spectre V2 is the only one which can attack the host system from the guest VM. It's vital to know the detailed process of the attack. Gavin Guo will give a detail explanation and an example of how to attack the host system. Besides, v1/v3/v4 are also introduced in the slide.