Abstract: Various embodiments of the present invention are directed to efficient and robust methods by which virtual-machine monitors can recognize individual instructions and blocks of instructions within guest-operating-system code. In a described embodiment of the present invention, the guest operating system recognizes the instructions by recognizing an overall form, or pattern, for the instruction as well as the values of various fields within the instruction that may change with re-compilations and/or re-linking of guest operating system code.

Abstract: Various embodiments of the present invention are directed to methods by which a virtual-machine monitor can introduce branch instructions, in order to emulate privileged and other instructions on behalf of a guest operating system, into guest-operating-system code residing on virtually aliased virtual-memory pages. In a described embodiment of the present invention, the virtual-machine monitor physically aliases each virtual alias for a particular physical memory page by allocating a physical page for the virtual alias, copying the original contents of the physical memory page to the allocated physical page, or physical alias page, and subsequently patching each physical alias page appropriate to the physical address of the physical alias page.

Abstract: In one embodiment of the present invention, a virtual-machine monitor detects entry and exit from guest-operating system code, storing the values of a set of high-order floating point registers in memory on entry, and restoring the values of the set of high-order floating point registers on exit. The virtual-machine monitor can then use the set of high-order floating point registers as scratch registers for emulation of guest-operating-system instructions. In alternative embodiments of the present invention, a virtual-machine monitor obtains scratch registers for any code that the virtual-machine monitor can detect entry into and exit from, and for which a set of infrequently used registers can be identified, by storing the current contents of the set of registers upon detected entry into the code and restoring the original contents of the set of registers upon exit from the code, emulating access to the set of registers in the code by memory-access operations.

Abstract: Various embodiments of the present invention are directed to efficient methods by which virtual-machine monitors can introduce instructions into guest-operating-system code. In one embodiment of the present invention, the virtual-machine monitor builds instructions dynamically, at insertion time, using specified values for fields within the instruction. In one embodiment of the present invention, the instructions and instruction field values are stored in an instruction-block-representing data structure.