Research Of Virtualization Technology And Implementation Of Direct PCI Device Access

Within a few years, Virtualization Technology grows rapidly with the support of major IT companies. But very limited effort is made to support direct device access in full virtualization. Through direct device access, the intervention of Virtual Machine Monitor can be decreased to the lowest degree and the cost of hardware emulation can be saved. Meanwhile, current device drivers can be used by guest Operating Systems to support abundant hardware stably and efficiently.To make the system virtual machine a product, this paper educed the I/O efficiency problem and offered a solution and implementation based on the latest xen 3.0 and processor-level virtualization technology.By analyzing I/O architectures of xen and VMWare Workstation, this paper concludes that it's hard for emulated hardware to overcome the burden and complexity. A new approach is given to support direct device access in full virtualization, and a solution is accomplished for PCI devices based on xen 3.0. By analyzing the source code of xen device model and the related, a hardware resource manager is implemented based on xen device model. It is enabled by Intel VT-x technology that virtual machine can use devices without the intervention of device model, so the I/O path is shorten. Moreover, the key problem of I/O resources conflicts between guest Operating System and Domain 0 is introduced and corresponding solutions are given for two kinds of I/O resources. For memory-mapped I/O region, shadow page tables are used to implement a new mapping. For isolated I/O resources, register functions are used to implement the conversion.The research on Virtualization Technology will improve the software development at the Operating System level. By implementing a prototype machine with direct PCI device access support, a beneficial approach is made to improve the architecture of Virtual Machine Systems.