Embedded Systems Design - August 2008 - (Page 20)

0808esd.p16to24 7/18/08 11:53 AM Page 20 cover feature The TenAsys embedded VMM (eVM) uses Intel Virtualization Technology to partition processor resources among each guest operating system. Microsoft Windows Guest OS Embedded and real-time application Shared memory Windows kernel and drivers Guest kernel + drivers Dedicated I/O Dedicated RAM Windows RAM Windows I/O Shared & virtual I/O Shared & virtual I/O device drivers TenAsys eVM Embedded virtual machine manager Figure 1 files of a guest operating system may be modified to trap supervisor-level CPU instructions, requiring the VMM to emulate these instructions. Instruction emulation slows down the execution speed of the guest operating system, and the need to “fix up” binary files limits guest operating systems to those that have been certified for use with The downside to such VMM trickery is a the VMM. VIRTUALIZATION decrease in performance and limited Virtualization techTECHNOLOGY IN MULTICORE CPUs compatibility among guest operating systems. nology built into the CPU is designed to Until the availability of overcome these probIntel VT (widely introlems. For example, Intel VT adds an duced on the Intel Core microarchitec- virtualization technology in the processor, include modifying the guest overarching operating mode, called ture), software-only VMMs running operating system’s binary code and VMX root, where a hypervisor exeon the x86 architecture encountered running guest operating systems at cutes with ultimate control of the CPU significant challenges. Both the VMM ring levels for which they were not hardware. A hypervisor that uses Intel and the guest operating system expect written.2 VT can intercept key supervisor-mode to maintain supervisor-level control over the hardware platform; however, The downside to such VMM trick- operations executed by a guest operating system without requiring knowlabsent some form of cooperation beery is a decrease in performance and tween the VMM and the guest limited compatibility among guest op- edge of the guest operating system’s binaries or internals.2 operating systems (aka “para-virtualerating systems. For example, binary quires multicore processors and needs an assist from hardware-virtualization technology in the processor to ensure that each virtual machine has low interrupt latency, direct access to specialized I/O, and the assurance that the VMM will not “time slice away” the guest operating system and its applications. 20 AUGUST 2008 | embedded systems design | www.embedded.com ization”), the VMM must resort to time-consuming and CPU-intensive “tricks.” Supervisor-level control can be reliably maintained by only one software system, resulting in a conflict between the VMM and the guest operating system. The tricks a VMM must use, without the support of hardware- http://www.embedded.com

Table of Contents Feed for the Digital Edition of Embedded Systems Design - August 2008

Embedded Systems Design - August 2008 Contents Number Include Parity Bit Programmer's Toolbox Cover Feature: Virtualization for Embedded X86 Multiprocessor Applications Wanted: Industry Standards for Benchmarking Embedded VMM Hypervisors Achieving Cache Coherence in a MIPS32 Multicore Design Memory Allocation in C Advertising Index Break Points Marketplace

Embedded Systems Design - August 2008

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