Embedded Systems Design - August 2008 - (Page 23)

0808esd.p16to24 7/21/08 10:30 AM Page 23 cover feature An embedded VMM supports three guest operating systems on a quad-core processor RTOS VM RTOS VM Windows VM Embedded virtual machine manager DSP CPU RTOS CPU GPOS CPU GPOS CPU Figure 2 physical resources among all the virtu- console device). In these instances, virA VMM FOR EMBEDDED tual devices exist to handle the real machines. Hardware-virtualization technology quirement to share the hardware A serious drawback of the server has made possible the emergence of an among multiple virtual machines. VMM model is the heavily virtualized embedded VMM (eVM) capable of supporting the demands of a real-time I/O model. Not only does virtualizing MULTIPLE RTOS SUPPORT all I/O seriously limit the number and operating system (RTOS) while simulThe application of an taneously hosting a generalembedded VMM is purpose operating system The AMP model of resource allocation is not limited to “dual (GPOS), such as Windows or useful where determinism and performance operating system, sinLinux. On a dual-core magle platform” on chine the eVM hypervisor are more important than equal access. dual-core systems; indedicates each guest operatcreasing the number ing system to a core, for a of processor cores on a platform invariety of I/O devices accessible with “dual-OS, single-platform” environcreases the possibilities. For example, the virtual machine, but it also has a ment, giving developers the means to significant impact on performance and three virtual machines could be hosted merge two disparate hardware platon a quad-core processor: Windows in determinism. forms into one. Figure 1 shows an exone virtual machine running on two The AMP model of resource alloample of the TenAsys embedded VMM cores and two embedded virtual macation is useful where determinism (eVM), which uses Intel VT to partichines, each containing a dedicated and performance are more important tion processor resources among each RTOS on each of the remaining cores. than equal access. The processor VT guest operating system. Take, for example, a conventional features can be used to isolate reA key difference between this emsystem consisting of a Windows comsources for use by a specific virtual bedded VMM and the server VMM puter serving the user-interface and model is how physical resources are al- machine and its guest operating sysenterprise nexus function, an RTOS tem rather than to create virtual I/O located to each virtual machine—parbox providing machine control, and a alleling the AMP versus the SMP mod- for shared access among multiple virDSP PCI card in the Windows box tual machines. els. Resources, such as CPU cycles, dedicated to high-performance nuEven in the AMP model, which is RAM, I/O, and interrupts, must be almeric algorithms, such as image prothe basis of the embedded hypervisor, located by any VMM. In the simplest cessing. Using an embedded hypervicase, a server VMM evenly multiplexes not all I/O is required to be exclusive. sor as shown in Figure 2, what was Some will be shared (such as the hard these resources among the virtual mapreviously three separate (and expendisk, enterprise Ethernet adapter, and chines, attempting to fairly distribute www.embedded.com | embedded systems design | AUGUST 2008 23 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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