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Technologies
3 Technologies
3.1 Intel ® Virtualization Technology
Intel Virtualization Technology (Intel VT) makes a single system appear as multiple
independent systems to software. This allows multiple, independent operating systems
to run simultaneously on a single system. Intel VT comprises technology components
to support virtualization of platforms based on Intel architecture microprocessors and
chipsets. Intel Virtualization Technology (Intel VT-x) added hardware support in the
processor to improve the virtualization performance and robustness. Intel Virtualization
Technology for Directed I/O (Intel VT-d) adds chipset hardware implementation to
support and improve I/O virtualization performance and robustness.
Intel VT-x specifications and functional descriptions are included in the Intel ® 64 and
IA-32 Architectures Software Developer’s Manual, Volume 3B and is available at:
http://www.intel.com/products/processor/manuals/index.htm.
The Intel VT-d spec and other VT documents can be referenced at:
http://www.intel.com/technology/virtualization/index.htm.
3.1.1 Intel ® VT-x Objectives
Intel VT-x provides hardware acceleration for virtualization of IA platforms. Virtual
Machine Monitor (VMM) can use Intel VT-x features to provide improved reliable
virtualized platforms. By using Intel VT-x, a VMM is:
• Robust—VMMs no longer need to use paravirtualization or binary translation. This
means that they will be able to run off-the-shelf OSs and applications without any
special steps.
• Enhanced—Intel VT enables VMMs to run 64-bit guest operating systems on IA
x86 processors.
• More reliable—Due to the hardware support, VMMs can now be smaller, less
complex, and more efficient. This improves reliability and availability and reduces
the potential for software conflicts.
• More secure—The use of hardware transitions in the VMM strengthens the
isolation of VMs and further prevents corruption of one VM from affecting others on
the same system.
3.1.2 Intel ® VT-x Features
The processor core supports the following Intel VT-x features:
• Extended Page Tables (EPT)
— EPT is hardware assisted page table virtualization
— It eliminates VM exits from guest OS to the VMM for shadow page-table
maintenance
• Virtual Processor IDs (VPID)
— Ability to assign a VM ID to tag processor core hardware structures (such as
TLBs)
— This avoids flushes on VM transitions to give a lower-cost VM transition time
and an overall reduction in virtualization overhead.
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