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Hyper-V &Processors Architectural Overview

 People still have some confusion about the technique that Virtual Processor for VM on Hyper-V use. 


Hyper-V uses a hypervisor-based architecture and leverages the driver model of Windows for broad hardware support. The hypervisor partitions a server into containers of CPU and memory. As a micro-kernel, it provides mechanisms for inter-partition communication upon which our new high-performance synthetic I/O architecture is built. The root partition owns physical I/O devices and provides services including I/O implemented by the virtualization stack to the child partitions.

The virtualization stack implements emulated I/O devices such as an IDE controller and a DEC 21140A network adapter. However, it is expensive to virtualize such devices. Sending a single I/O might require multiple trips between the virtualization stack and child partition. Instead, Hyper-V exposes synthetic I/O devices that are specially designed for VM environments. These devices are attached to VMBus, which is a plug-and-play capable bus that uses shared memory for efficient inter-partition communication. The Windows guests detect the devices on VMBus and loads the appropriate drivers

Synthetic I/O in Hyper-V uses a client-server architecture with Virtualization Service Providers (VSPs) in the root and Virtualization Service Clients (VSCs) in the child. This architecture significantly reduces the cost of sending an I/O. Virtual Server customers should observe a major reduction in CPU usage in I/O-intensive loads when they migrate their VMs to Hyper-V.





Hyper-V and the Processors


The hypervisor handles the interrupts to the processor, and redirects them to the respective partition. Hyper-V can also hardware accelerate the address translation between various guest virtual address spaces by using an IOMMU (Input Output Memory Management Unit) which operates independent of the memory management hardware used by the CPU. An IOMMU is used to remap physical memory addresses to the addresses that are used by the child partitions.


The Virtualization Infrastructure Driver (VID) is the kernel mode component of the virtualization stack.

The VID provides partition management services, virtual processor management services, memory management services for partitions.


At last, we could change the processor percentage while VM is working. However, you only able to change the following parts:


-Virtual Machine reserve

-Virtual Machine limit

-Relative Weight


View the article below to see what these settings mean:


Configuring CPU resources for virtual machines





 Firstly, we must know that all processors inside the VM are Virtual Processors.

Guest OS does not have access to the physical processor, nor do they handle the processor interrupts.

 Instead, they have a virtual view of the processor and run in a virtual memory address region that is private to each guest partition.

To understand that well we must get a look at Hyper-V architecture.

 Hyper-V Architecture

Hyper-V (formerly known as “Viridian” and Windows Server Virtualization (WSv)) offers a completely new virtualization architecture.


Hyper V Architecture

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