Knowledge Lecture: What is Intel VT Virtualization Technology?

  

Intel introduced virtualization technology on its hardware products to improve the processor performance of servers running virtualized platforms from hardware. To gain a deeper understanding of Intel VT (Intel Virtualization Technology) technology and its different applications in processors, chips and I/O devices, we need to first understand what factors limit virtualization performance under traditional platforms.

Virtualization technology allows IT professionals to run multiple different virtual machines on a single physical server. This requires a physical server to create and manage multiple virtual systems. The core of virtualization technology lies in VMM (virtual machine monitor), which is the key to successfully completing multiple virtualization related tasks. VMM manages multiple operating system instances at the same time, and manages the switching process between these instances, so that each virtual machine can access hardware resources such as the underlying processor, memory, and local disk. It allocates computing resources between different instances through a competitive mechanism, while ensuring relative independence between different virtual machines.

Prior to 2005, the performance issues of the virtualization platform were mainly focused on the lack of a corresponding internal instruction set in the processor, so there was no guarantee that the virtualization task of the processor could be completed efficiently. The allocation of these virtualization tasks is implemented at the software level, and therefore performs very poorly in terms of virtual machine experience, resource control, and efficiency. Simply put: the virtual machine does not work well, and the performance of the server is affected. Both AMD and Intel are working on new processor upgrades to meet the new virtualization needs. These upgrades reduce (or even eliminate) resource contention and limitations between guest operating systems, greatly improving the security and performance of virtual machine instances.

Intel VT, originally developed under the code name "Vanderpool", first appeared in Intel's development plan based on the "Nehalem" architecture of the CPU system. The current technology has been extended to multiple Intel product lines, including Pentium 4, the Celeron, Core i5, Core i7, Core Solo, Core 2 Duo, Core 2 Extreme, Core 2 Quad, Xeon and others. Device. And it's important to understand that not all of the latest Intel processors (not every model in the above series) can support VT-x: this is considered a high-end PC and server. new technology. For a list of Intel processors that can support VT-x, refer to the relevant content on the Intel website.

Intel has developed a series of different instruction sets for providing hardware layer virtualization technology. VT-x is the best-in-class instruction set, adding migration, priority, and memory management capabilities to multiple Intel processors. In contrast, the VT-d instruction set improves the Intel chip's ability to support virtualization, allowing the chipset to allocate certain I/O device resources to specific virtual machines. VT-c introduces virtualization support for certain I/O devices, such as network switches.

Memory control and management play a pivotal role in hardware-based virtualization. The Intel VT-x instruction set eliminates the impact of VMM intervention when it comes to software-based resource allocation. Moreover, the memory management function has been added to the Extended Page Tables, and this function is necessary for the transfer of control of the processor resources between different virtual machines.

Intel Flex's FlexPriority feature helps manage conflicts between processors. Since interference from some devices and other applications often affects processor performance, Intel has added a task priority arbitration register to determine the priority of the task. Only those interrupts with a higher priority than the existing running task can be executed immediately. Low-priority tasks are placed on the stack and are executed when the load program is licensed. The Intel VT FlexMigration feature allows virtual machines to be quickly and easily migrated between multiple physical servers supporting the Intel VT-x instruction set in a virtualized platform. One of the key points we need to note is that this extended migration feature is not available for AMD processor platforms. Migration between platforms of different processor vendors can lead to serious performance problems and even system failures.

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