[$] Moving physical pages from user space

Processes in a Linux system run within their own virtual address spaces.
Their virtual addresses map to physical pages provided by the hardware, but
the kernel takes pains to hide the physical addresses of those pages;
processes normally have no way of knowing (and no need to know) where their
memory is located in physical memory. As a result, the system calls for
memory management also deal in virtual addresses. Gregory Price is
currently trying to create an exception to this rule with a
proposal for a new system call that would operate on memory using physical
addresses.