Real-time Virtualization Research Articles

BlueVisor: Time-Predictable Hardware Hypervisor for Many-core Embedded Systems

Whilst virtualization was once restricted to large-scale computing platforms, and it is now widely deployed on modern embedded computing systems. This has been driven by the availability of hardware support which alleviates the performance penalties incurred by traditional software virtualization technologies. In the domain of hard real-time systems, specialist virtualization technology which respects restricted timing requirements and constraints can be deployed to allow sharing of processors. However, other aspects of the embedded system (I/O, memory, and communication) are harder to analyse. In this paper, we argue that in order to support real-time virtualization on modern embedded systems, additional system-wide hardware support is required. We propose BlueVisor, an analyzable and scalable hardware hypervisor for many-core embedded systems, which enables time-predictable CPU, memory, and I/O virtualization, as well as supporting a fast interrupt handler, and inter-VM communication. We describe the design and implementation of the real-time hypervisor and demonstrate how a BlueVisor-based virtualization system can be leveraged to meet real-time requirements with significant improvement in system performance, and with a low-performance cost when executing different types of software.

Real-time virtualization with Xvisor

Embedded virtualization has gained attention in recent years due to increasing usage of embedded systems in cyber-physical systems and the Industry 4.0 revolution. Especially in combination with multi-core embedded systems, virtualization reduces the number of embedded systems and simultaneously delivers a secure and separated environment in each virtualized system. Applications in such cyber-physical systems often require real-time guarantees with hard deadlines. To guarantee those real-time constraints in virtualization, both hypervisor and guest operating system must support real-time scheduling. Selecting the optimal scheduling algorithm on both scheduling levels is hard and is only optimal for the analysed application. Due to the multiple scheduling levels, a set of scheduling algorithm combinations must be analysed which is too costly without analysis on higher abstraction levels. By using an analysis methodology to find this optimal combination using higher abstraction levels analysis, we reduce the set at every abstraction level. In this paper, we present a real-time hypervisor, based on Xvisor, for multi-core embedded systems. We modified the hypervisor to support real-time scheduling and the compositional schedulability analysis and validated the analysis methodology using this embedded hypervisor.

A 28-nm Automotive Flash Microcontroller With Virtualization-Assisted Processor Supporting ISO26262 ASIL D

In the autonomous driving era, automotive architecture has been rapidly progressing toward electronic control unit (ECU) integration and centralization. Advanced vehicle control is becoming increasingly important for safe driving. It requires microcontroller unit (MCU) integration, the highest automotive safety integrity level (ASIL), and network performance improvement. A 28-nm 600-MHz automotive flash MCU has been developed for next-generation automotive architecture. The MCU for vehicle control integrates three key features: a virtualization-assisted processor (VAP) for functional safety, a built-in self-test in the field (field-BIST) at a sleep resume (SR) BIST for functional safety, and a serial gigabit media independent interface (SGMII) for the in-vehicle network. The VAP helps the hypervisor to realize real-time virtualization to execute several different virtual machines without interference. The SR-BIST realizes random hardware failures per hour of 10−8 in various automotive applications. In the SGMII circuit, we used 5-V transistors for high reliability despite their narrow bandwidth. The automotive MCU satisfies the ISO26262 ASIL D system requirements with a low power consumption of 0.52 W. The VAP can realize the severe automotive control hard real time capability.

Runtime performance evaluation and optimization of type-2 hypervisor for MIPS64 architecture

Over the last decade, virtualization technologies have seen unprecedented growth in the system-level domain and promptly have moved to the embedded system domain. While there are numerous applications of virtualization for off-the-shelf hardware such as security, sandboxing, testing tools, etc. However, there are few open-source virtualization solutions available for embedded systems. For real-time virtualization, good runtime performance is a deterministic factor for its practical use in the embedded domain. In this paper, the internal architecture of HTTM (an open-source type-2 hypervisor for MIPS64 architecture) was thoroughly analyzed. ISA virtualization unit and execution cycle control were two primary units that were profiled and explored for optimization. Dynamic Binary Translation (DBT) unit was modified to generate highly efficient code. While the reduction in switching between the translated code and management layer improved the overall execution cycle. The implementation of these strategies resulted in a 72–91% improvement in bandwidth benchmarks. Similarly, latency benchmarks show a 2–92% improvement from its vanilla version. Collectively producing an overall 1–5 times the improvement in execution time. The performance of optimized HTTM is also compared with Quick Emulator (QEMU). HTTM performs 44–80% better than QEMU in bandwidth benchmarks while QEMU performs better in latency operations.

Predictable Shared Cache Management for Multi-Core Real-Time Virtualization

Real-time virtualization has gained much attention for the consolidation of multiple real-time systems onto a single hardware platform while ensuring timing predictability. However, a shared last-level cache (LLC) on modern multi-core platforms can easily hamper the timing predictability of real-time virtualization due to the resulting temporal interference among consolidated workloads. Since such interference caused by the LLC is highly variable and may have not even existed in legacy systems to be consolidated, it poses a significant challenge for real-time virtualization. In this article, we propose a predictable shared cache management framework for multi-core real-time virtualization. Our framework introduces two hypervisor-level techniques, vLLC and vColoring, that enable the cache allocation of individual tasks running in a virtual machine (VM), which is not achievable by the current state of the art. Our framework also provides a cache management scheme that determines cache allocation to tasks, designs VMs in a cache-aware manner, and minimizes the aggregated utilization of VMs to be consolidated. As a proof of concept, we implemented vLLC and vColoring in the KVM hypervisor running on x86 and ARM multi-core platforms. Experimental results with three different guest OSs (i.e., Linux/RK, vanilla Linux, and MS Windows Embedded) show that our techniques can effectively control the cache allocation of tasks in VMs. Our cache management scheme yields a significant utilization benefit compared to other approaches while satisfying timing constraints.

Virtualizing Programmable Logic Controllers: Toward a Convergent Approach

Modern programmable logic controllers (PLCs) are pervasive components in industrial control systems (ICSs) such as supervisory control and data acquisition, designed to control industrial processes autonomously or as part of a distributed system topology. Its success may be explained by its robustness and reliability, being one of the most enduring legacies on modern ICS, despite having evolved very little over the last years. This letter proposes an x86-based virtual PLC (vPLC) architecture that decouples the logic and control capabilities from the I/O components, while virtualizing the PLC logic within a real-time hypervisor. To demonstrate the feasibility of this concept, the topic of real-time virtualization for x86 platforms is analyzed, together with an evaluation study of the properties of real-time workloads in partitioned hypervisor environments.

다중 코어 기반의 실시간 가상화 시스템을 위한 이종 운영체제 통합 성능 분석 방법에 관한 연구

This paper describes a method that is integrated trace for real-time virtualization environment. This method has solved the problem that the performance trace may not be able to analyze integrated method between heterogeneous operating systems which is consists of real-time operating systems and general-purpose operating system. In order to solve this problem, we have attempted to reuse the performance analysis function in general-purpose operating system, thereby real-time operating systems can be analyzed along with general-operating system. Furthermore, we have implemented a prototype based on ARM Cortex-A15 dual-core processor. By using this integrated trace method, real-time system developers can be improved productivity and reliability of results on real-time virtualization environment.

A super base station based centralized network architecture for 5G mobile communication systems

To meet the ever increasing mobile data traffic demand, the mobile operators are deploying a heterogeneous network with multiple access technologies and more and more base stations to increase the network coverage and capacity. However, the base stations are isolated from each other, so different types of radio resources and hardware resources cannot be shared and allocated within the overall network in a cooperative way. The mobile operators are thus facing increasing network operational expenses and a high system power consumption. In this paper, a centralized radio access network architecture, referred to as the super base station (super BS), is proposed, as a possible solution for an energy-efficient fifth-generation (5G) mobile system. The super base station decouples the logical functions and physical entities of traditional base stations, so different types of system resources can be horizontally shared and statistically multiplexed among all the virtual base stations throughout the entire system. The system framework and main functionalities of the super BS are described. Some key technologies for system implementation, i.e., the resource pooling, real-time virtualization, adaptive hardware resource allocation are also highlighted.

Challenges in real-time virtualization and predictable cloud computing

Cloud computing and virtualization technology have revolutionized general-purpose computing applications in the past decade. The cloud paradigm offers advantages through reduction of operation costs, server consolidation, flexible system configuration and elastic resource provisioning. However, despite the success of cloud computing for general-purpose computing, existing cloud computing and virtualization technology face tremendous challenges in supporting emerging soft real-time applications such as online video streaming, cloud-based gaming, and telecommunication management. These applications demand real-time performance in open, shared and virtualized computing environments. This paper identifies the technical challenges in supporting real-time applications in the cloud, surveys recent advancement in real-time virtualization and cloud computing technology, and offers research directions to enable cloud-based real-time applications in the future.

Performance Tuning Towards a KVM-based Embedded Real-time Virtualization System

Virtualization is a fundamental component in cloud computing because it provides numerous guest VM transparent services, such as live migration, high availability, rapid checkpoint, etc. Utilizing virtualization technology to combine real-time operating system (RTOS) and off-the-shelf time-sharing general purpose operating system (GPOS) is attracting much more interest recently. Such combination has the potential to provide a large application base, and to guarantee timely deterministic response to real-time applications, yet there remain some issues, such as responsiveness of RTOS running on top of a virtual machine (VM), system performance and CPU resource utilization rate, etc. In this paper we propose an embedded real-time virtualization architecture based on Kernel- Based Virtual Machine (KVM), in which VxWorks and Linux are combined together. We then analyze and evaluate how KVM influences the interrupt-response times of VxWorks as a guest operating system. By applying several real-time performance tuning methods on the host Linux, we will show that sub-millisecond interrupt response latency can be achieved on the guest VxWorks. Furthermore, we also find out that prioritization tuning results in waste of CPU resources when RTOS is not executing real-time tasks, so we design a dynamic scheduling mechanism--co-scheduling to improve system performance. Experimental results with SPEC2000 and bonnie 1.4 load, show that this new architecture tuned by CPU shielding, prioritization and co-scheduling, can achieve better real-time responsiveness and system performance.

Basics of virtual machine migration on heterogeneous architectures for self-optimizing mechatronic systems

The combination of virtualization and heterogeneous multi-processor architectures supports the development of efficient platforms for self-optimizing mechatronic systems, which are characterized by varying resource requirements. Virtualization addresses dependability issues and adds runtime flexibility to provide an appropriate resource management. Real-time requirements have to be met and existing real-time virtualization solutions are characterized by a static mapping of virtual machines to processors and do not use the full potential of heterogeneous architectures. The sketched architecture applies migration and emulation to realize a dynamic assignment of virtual machines to processors. This work identifies the necessary conditions for migration and the degree of communication between hypervisor and operating system that is indispensable for migration decisions. System virtualization is an approach of coarse-grained system consolidation, for which reason implementation issues and possibilities to reduce the high overhead are discussed. The implementation of a real-time capable virtual machine migration requires paravirtualization, that is to say a modification of the guest operating systems. The need to modify the guest operating system is outweighed by the advantages in terms of flexibility of an explicit communication and the resulting cooperation of hypervisor and guest operating system.