Memory Overcommit by Using an Emulated IOMMU in a Computer System without a Host IOMMU

A system comprising:

• host memory to store a hypervisor;
• a computer coupled to the host memory to host a plurality of virtual machines and the hypervisor and
• a device coupled to the computer to perform direct memory access (DMA) to a buffer managed by a guest operating system of one of the virtual machines,
• wherein the hypervisor, in response to a request from a guest operating system on one of the virtual machines for mapping a guest address to a bus address, translates the guest address to a host address, pins a memory page containing the host address to keep the memory page in the host memory, and returns the host address to the guest operating system to allow the device to use the host address as the bus address for direct memory access (DMA) to a buffer managed by the guest operating system.

A computer readable storage medium including instructions that, when executed by a processing system, cause the processing system to perform a method comprising:

• receiving a request from a guest operating system for mapping a guest address to a bus address, the guest operating system being run on one of a plurality of virtual machines hosted by a computer;
• translating the guest address to a host address;
• pinning a memory page containing the host address to keep the memory page in host memory;
• and
• returning the host address to the guest operating system to allow a device to use the host address as the bus address for direct memory access (DMA) to a buffer managed by the guest operating system.