1. A computer system comprising: a host system including at least one hardware processor and a hardware memory; and one or more virtual machines, each configured to run on said at least one hardware processor using regions of the hardware memory that have been allocated thereto, wherein each of the virtual machines includes (i) a guest operating system that allocates guest physical memory to software modules that are executed therein, and (ii) a memory reservation software module that is executed in response to a memory quantity request from the host system, and wherein a portion of the hardware memory corresponding to the guest physical memory that is allocated to the memory reservation software module by the guest operating system is made available to the host system for reallocation.