Goals for a GNU VMM

Less centrality
Mach provides too much functionality in the kernel
A single large VMM would not be better
Should be stackable

External pagers
Mandatory: the Hurd relies heavily on this feature for translators

Eviction Policy
It must be more flexible
Tasks should be completely self-paged

Resource limits
Must design an interface
Cannot be done centrally
Servers render services for clients
Servers are not necessarily trusted by the system
Servers cannot be trusted by a central resource server
Clients should supply required resources to servers