Research On Key Technology Of Device Virtualization

With the development of virtualization technology, the processor virtualization and memory virtualization's function are gradually consummating , and their performance are also increasing. But the device virtualization is still the bottleneck that restricts the overall performance of virtualization, therefore, providing efficient device virtualization model for VMM is one of the problems need to be resolved in system virtualization urgently.Device virtualization's goal is to provide reusable virtual device for VM, and meet the VM transparently accessing to equipment while ensuring the reliability, efficiency and safety of device accessing. The main problems of existing device virtualization model are VMM security risk caused by its own drivers, inconvenience of equipment replacement and system upgrades, IO processing delays, etc.To solve these problems, the paper uses another form of Separation-Driven model, it uses multi-core platform to transfer privileged domains from the VM to IO processors. This IO processor runs in a single machine with VMM at the same position, it can eliminate the IO processing delays caused by scheduling while avoiding the frequent privilege level switching. On this basis, the paper designs a common device virtualization model, including the following four aspects:1. Construction of virtual device. This part uses the VM booting's dependence on its own BIOS, completes the data configuration in the VM's BIOS according to real system configuration and user's requirements to provide a virtual device image for VM, it allows VM to finish the detection of equipment through the virtual BIOS.2. IO instruction interception and analysis. This part uses the processor or memory virtualization technology to intercept the IO requests sented by VM to virtual device, further analysis the information of IO requests to obtain the specific contents of IO request and provide sources of IO information for device model.3. Conversion for data addresses space. In the IO request processing, data needs to be transmitted among the client address space, VMM address space and IO shared data area, this part completed the address translation among this three spaces.4. Key device simulation. This part uses software simulation to complete general implementation of the device simulation and achieve the basic functions of DMA and NIC. Through the simulation of DMA and NIC, VMM can respond to VM's DMA requests and complete part of the network transfer function, with good performance.Test results show that, the performance of DMA virtualization operation implemented in paper compared with the performance of DMA operation in non-virtualized environment has nearly 15% of the loss, and NIC implemented in paper also has about 22% performance loss, these performance are slightly higher than the current DMA and NIC virtualization, but comparing with non-virtualized environment, there is a certain gap. It shows that device virtualization model designed in the paper to certain extent, can improve IO performance, with general and stable characteristics, and it can provide guidance for the next design and improvement of the system virtualization.