1. A method for dynamic CPU resource management, comprising: collecting CPU usage information for a virtual machine, the virtual machine having an allocated CPU share; determining a dynamic priority for the virtual machine based on a specified priority for the virtual machine; and dynamically changing the allocated CPU share of the virtual machine, as needed, based on the collected CPU usage information for the virtual machine and the determined dynamic priority for the virtual machine, wherein dynamically changing the CPU share of the virtual machine further comprises: increasing the CPU share of the virtual machine when it is determined that the collected CPU usage information indicates CPU usage of the virtual machine relative to CPU usage of other virtual machines is equal to or higher than the allocated CPU share of the virtual machine; or decreasing the CPU share of the virtual machine when it is determined that the collected CPU usage information indicates CPU usage of the virtual machine relative to CPU usage of other virtual machines is substantially lower than the allocated CPU share of the virtual machine.