Host Passthrough for Hardware Identification Instructions
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Solution Overview
Problem
Existing virtualization technologies incur performance degradation due to the overhead of VM exits and reentries, which are necessary for handling privileged events and resource access, especially when executing hardware identification instructions.
Innovation Solution
The implementation of a host passthrough mechanism that allows hardware characteristics to be communicated to virtual machines without requiring a VM exit, by using a hardware identification instruction and conditional execution based on configuration state information stored in the VMCS.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If VM exits and reentries are used to handle hardware identification instructions, then hardware information can be communicated to virtual machines, but performance degradation occurs due to overhead
Solution Approach 1:
The patent extracts the hardware identification functionality from the privileged VM exit path and implements it directly in the virtual machine through a hardware identification instruction. This allows the virtual machine to obtain hardware information (such as processor type, cache configuration, and other architectural details) without requiring control transfer to the hypervisor, thereby eliminating the performance overhead associated with VM exits while maintaining accurate hardware information communication.
2Measurement precision
If VM exits are performed for hardware identification, then accurate hardware information is obtained, but execution time increases
Solution Approach 1:
The patent implements hardware identification capabilities directly within the virtual machine environment through dedicated instructions that query hardware status registers and configuration data. This preliminary action allows the virtual machine to obtain accurate hardware information (processor architecture, cache hierarchy, instruction set features) immediately during execution without the time penalty of exiting to the hypervisor, thus maintaining measurement precision while reducing execution time.
Data Source
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AI summary
Techniques and mechanisms for a host passthrough to be performed based on the execution of a hardware identification instruction with a virtual machine (VM). In an embodiment, a hypervisor process sets a value of a control parameter corresponding to a resource of the VM. The control parameter indicates whether the VM resource is authorized to avail of a host passthrough functionality of a processor which executes the hypervisor process. The control parameter is evaluated, based on a central processing unit identification (CPUID) instruction of a guest operating system which is executed with the VM, to determine whether the CPUID instruction is to result in a host passthrough or a VM exit. In another embodiment, a shared memory resource is searched to determine whether execution of the CPUID instruction is to retrieve information without the use of either the host passthrough or the VM exit.