Methods, systems, and apparatus, including computer programs encoded on computer storage media, for pre-fetching content. One of the systems includes a pre-fetcher configured to perform operations including determining, for a virtual machine executing on a device and using a first virtual machine physical address associated with the virtual machine, a second virtual machine physical address for data to pre-fetch for the execution of the virtual machine on the device, determining, using the second virtual machine physical address and an address mapping that associates virtual machine physical addresses for the virtual machine with device physical addresses for the device, a device physical address for the data, and requesting the data from a memory using the device physical address.