Techniques are described for enabling a virtual machine to be presented with an amount of available guest memory, where a hypervisor or other privileged component manages the mapping of the resources based at least in part on the capacity of resources one or more hosts. This enables resources to be effectively oversubscribed to on host computing devices that have a limited amount of total available resources but which are running multiple virtual machines. For example, each virtual machine on the device can be presented as having access to the total amount of available resources that are available on the device or more in some cases. In some cases, resources may be mapped to a plurality of hosts that have available resources.