StratoVirt Design

Overview

StratoVirt is an open-source lightweight virtualization technology based on Linux Kernel-based Virtual Machine(KVM); StratoVirt reduces memory resource consumption and improves VM startup speed while retains isolation capability and security capability of traditional virtualization; StratoVirt can be applied to microservices or serverless scenarios such as function computing; StratoVirt reserves interface and design for importing more features, even standard virtualization;

Architecture

The following figure shows StratoVirt's core architecture which consist of three layers from top to bottom;

• OCI compatibility API: StratoVirt uses the QMP protocol to communicate with external systems and is compatible with OCI;
• BootLoader: StratoVirt uses a simple BootLoader to fast load the kernel image, instead of the traditional cumbersome BIOS and Grub boot modes, to achieve fast boot;
• Lightweight: To improve performance as well as reduce the attack surface, StratoVirt minimizes the simulation of user-mode devices; KVM simulation devices and paravirtualization devices, such as GIC, serial, RTC and virtio devices, are used;

Features

• High isolation ability based on hardware;
• Fast cold boot: Benefit from the minimalist design, StratoVirt could boot a microVM in 50ms;
• Low memory overhead: StratoVirt works with a memory footprint at 4MB;
• IO enhancement: StratoVirt offers normal IO ability with minimalist IO device emulation;
• OCI compatibility: StratoVirt works with isula and kata container, and can be integrated in Kubernetes ecosystem perfectly;
• Multi-platform support: Fully support for Intel and Arm platform;
• Expansibility: StratoVirt reserves interface and design for importing more features, even expand to standard virtualization support;
• Security: lower than 35 syscalls while running;

Implementation

Running Architecture

• StratoVirt VM is an independent process in Linux. The process has two types of threads: main thread and VCPU thread;
  • The main thread is a cycle for asynchronous collecting and processing events from external modules, such as a VCPU thread;
  • Each VCPU has a thread to process trap events of this VCPU;

Restrictions

• Only the Linux operating system is supported; The recommended kernel version is 4.19;
• Only Linux is supported as the client operating system, and the recommended kernel version is 4.19;
• StratoVirt is fully tested on openEuler;
• Supports a maximum of 254 CPUs;