The goal of this project is to enhance performance of virtual machines and simplify the design of the virtual machine monitor by running 32-bit x86 operating systems in x86-64 mode. In order to do so, 32-bit operating system binary code is translated into x86-64 binary code via "widening binary translation"; x86-32 code is "widened" into x86-64 code. The main challenge of widening BT is emulating x86-32 legacy segmentation in x86-64 mode. Widening BT's solution is to emulate segmentation in software. Most of the overhead for software segmentation can be optimized away. The main contribution of widening BT is simplification of the VMM, which reduces the human cost of maintaining a complicated VMM. Widening BT also improves performance of 32-bit guest operating systems running in virtual machines and demonstrates the independence of virtual machines from physical hardware. With widening BT, legacy hardware mechanisms like segmentation can be dropped. Therefore widening BT reduces hardware's burden of backwards-compatibility, encouraging software/hardware co-design.
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