Life of Interrupts: Virtualization


Interrupt handling is one of the critical subsystem in the hypervisor (HV). It is critical both from correctness and performance perspective. Hyper-V supports multi-processor systems and uses many optimizations to improve performance for interrupt virtualization.

Interrupt handling is done via APIC emulation. For each vCPU, a vAPIC is created in the hypervisor. These vAPIC behaves similar to APIC in a physical system and provide interrupt support to virtual machines. To support operating systems that are not APIC aware, PIC emulation is provided using virtual wire mode as specified in Intel multiprocessor specifications.

In this post, I would talk about how interrupts are virtualized in Hyper-V environment and discuss some of the performance optimizations. (more…)

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Life of Interrupts: Background

In this series of posts, I am going to talk about interrupt handling in a virtualized environment (specifically Hyper-V). This discussion would also include interrupt handling on systems that have IOMMU based interrupt remapping support. Interrupt remapping is required in Hyper-V for supporting SR-IOV enabled devices and device assignment to virtual machines.

The series is mostly written from software perspective and hardware details are only provided where necessary for understanding of the concepts. The series is focused on x86/x64 based architectures though the concepts described here can be applied to other architectures. (more…)

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