Efficient Virtualization of Input/Output Completions for a Virtual Device

A virtualized computer system comprising:

• a host hardware platform;
• a physical device;
• at least one virtual machine that runs as a guest on the host hardware platform, that has a guest operating system and at least one virtual processor, and that submits I/O requests to at least one virtual device that corresponds to the physical device, a system for virtualizing I/O completions;
• a backing device that backs the virtual device;
• an intermediate software layer that forms an interface between the hardware platform and the virtual machine(s) and that includes computer-executable code:
• for scheduling deliveries to the virtual machine of I/O completion interrupts during emulation of the physical device according to timing parameters that are based at least partially on timing constraints of the physical device, said timing constraints including a nominal I/O completion delay time;
• for detecting an actual I/O completion interrupt from the backing device;
• for detecting a safepoint, that is, a point of execution of the virtual processor that indicates that the virtual processor is in a condition to receive an I/O completion interrupt;
• and
• for dispatching the I/O completion interrupt, such that, if the detected safepoint occurs before the nominal I/O completion delay time, the I/O completion interrupt is dispatched before the nominal I/O completion delay time;
• thereby enabling device emulation acceleration relative to limiting deliveries of said I/O completion interrupt to a schedule that is based on said timing parameters alone.