Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for measuring virtual machine metrics. In one aspect, a method includes initializing a virtual machine, the virtual machine being associated with virtual hardware comprising a virtual metrics device, the virtual metrics device being configured to report values of a virtual machine metric that measures the performance of the virtual machine; receiving data identifying the virtual machine metric and a virtual machine memory address to which the virtual machine writes values of the virtual machine metric; reading one or more values of the virtual machine metric from the virtual machine memory address; and generating a report based on the one or more metric values.