Abstract: An operating system in a virtual environment can obtain the current time of the processor that the OS is utilizing through a method for synchronizing timers on multiple processors with a standard reference time, such as the Coordinated Universal Time (UTC). A hypervisor controlling the processors obtains a number of synchronization values that, together with a local timer counter value, are utilized by the guest operating system to determine the physical processor time.

Abstract: A method and system for using writeable page tables to increase performance of memory address translation in computing environments utilizing a hypervisor. Guest operating systems are given temporary write-access to a page table page after the system confirms that such page is not part of the current address space (i.e., confirming that the page is part of a different page table from the one that is currently in use, such as a different user-space process). Alternatively, if the page is part of the currently running page table, the system invalidates the appropriate entry in the root page directory, thus “unlinking” it, and ensuring that the appropriate region of virtual address space is flushed from the translation lookaside buffer (TLB) in the current CPU and others that may be using it. After giving the OS write-access, the page is added to a validation queue.