The Design And Implementation Of An Efficient Device Access Model Based On Virtual Machines

With the rapid development of computer Technology, the virtualization technology has already been widely used in more and more fields, and became a new hotspot.I/O virtualization is an important part of virtualization technology, which plays a crucial role to improve the system performance. With Intel and AMD designing a series of CPUs with virtualization supporting, the performance of CPU and memory gets a great progress in virtual environment. However, I/O performance becomes the bottleneck in virtualization now. This is the reason why the efficient device access model(V-EDAM) is necessary to research.Firstly, This paper analyzes QEMU I/O model and three current popular device access models (Split I/O, Direct I/O, and Passthrough I/O) in details, and analyzes their strengths and weaknesses of their architecture. Secondly, V-EDAM which based on Split I/O model and used device driver domain and Passthrough I/O technology is presented in order to get better balance of device performance and sharing in full virtualization environment. By assigning a physical device to a specificed guest domain, V-EDAM makes that domain to be a device driver domain. Through separating device driver from host operating system, V-EDAM reduces the probability of host operating system's collapse and improves the stability and security of the entire virtual environment. V-EDAM is consisted of three modules: guest domain service module, driver domain service module and inter-domain communication module. The guest domain service module sends the I/O request. The inter-domain communication module captures the I/O requests, analyzes them and transmits them to the right domain. Driver domain service module provides I/O services and responses the I/O request. The inter-domain communication module is the core module in the V-EDAM.Finally, the paper provides a implementation of the V-EDAM in KVM for network devices and compares the performance between V-EDAM and other device access models. The result shows that V-EDAM achieves better performance and efficiency than QEMU I/O virtualization model and it has a better application value in KVM.The work is supported by 863 project―the virtual personal computer systems of multi-Dom calculation‖.