The SPLASH-2 suite of parallel applications has recently been released to facilitate the study of centralized and distributed shared-address-space multiprocessors. In this context, this paper has two goals. One is to quantitatively characterize the SPLASH-2 programs in terms of fundamental properties and architectural interactions that are important to understand them well. The properties we study include the computational load balance, communication to computation ratio and traffic needs, important working set sizes, and issues related to spatial locality, as well as how these properties scale with problem size and the number of processors. The other, related goal is methodological: to assist people who will use the programs in architectural evaluations to prune the space of application and machine parameters in an informed and meaningful way. For example, by characterizing the working sets of the applications, we describe which operating points in terms of cache size and problem size are representative of realistic situations, which are not, and which re redundant. Using SPLASH-2 as an example, we hope to convey the importance of understanding the interplay of problem size, number of processors, and working sets in designing experiments and interpreting their results.

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The SPLASH-2 programs: characterization and methodological considerations

Mobile computing continuously evolve through the sustained effort of many researchers. It seamlessly augments users' cognitive abilities via compute-intensive capabilities such as speech recognition, natural language processing, etc. By thus empowering mobile users, we could transform many areas of human activity. This article discusses the technical obstacles to these transformations and proposes a new architecture for overcoming them. In this architecture, a mobile user exploits virtual machine (VM) technology to rapidly instantiate customized service software on a nearby cloudlet and then uses that service over a wireless LAN; the mobile device typically functions as a thin client with respect to the service. A cloudlet is a trusted, resource-rich computer or cluster of computers that's well-connected to the Internet and available for use by nearby mobile devices. Our strategy of leveraging transiently customized proximate infrastructure as a mobile device moves with its user through the physical world is called cloudlet-based, resource-rich, mobile computing. Crisp interactive response, which is essential for seamless augmentation of human cognition, is easily achieved in this architecture because of the cloudlet's physical proximity and one-hop network latency. Using a cloudlet also simplifies the challenge of meeting the peak bandwidth demand of multiple users interactively generating and receiving media such as high-definition video and high-resolution images. Rapid customization of infrastructure for diverse applications emerges as a critical requirement, and our results from a proof-of-concept prototype suggest that VM technology can indeed help meet this requirement.

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The Case for VM-Based Cloudlets in Mobile Computing

Cloud computing has recently emerged as a new paradigm for hosting and delivering services over the Internet. Cloud computing is attractive to business owners as it eliminates the requirement for users to plan ahead for provisioning, and allows enterprises to start from the small and increase resources only when there is a rise in service demand. However, despite the fact that cloud computing offers huge opportunities to the IT industry, the development of cloud computing technology is currently at its infancy, with many issues still to be addressed. In this paper, we present a survey of cloud computing, highlighting its key concepts, architectural principles, state-of-the-art implementation as well as research challenges. The aim of this paper is to provide a better understanding of the design challenges of cloud computing and identify important research directions in this increasingly important area.

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Cloud computing: state-of-the-art and research challenges

Migrating operating system instances across distinct physical hosts is a useful tool for administrators of data centers and clusters: It allows a clean separation between hard-ware and software, and facilitates fault management, load balancing, and low-level system maintenance.By carrying out the majority of migration while OSes continue to run, we achieve impressive performance with minimal service downtimes; we demonstrate the migration of entire OS instances on a commodity cluster, recording service downtimes as low as 60ms. We show that that our performance is sufficient to make live migration a practical tool even for servers running interactive loads.In this paper we consider the design options for migrating OSes running services with liveness constraints, focusing on data center and cluster environments. We introduce and analyze the concept of writable working set, and present the design, implementation and evaluation of high-performance OS migration built on top of the Xen VMM.

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Live migration of virtual machines

This paper presents MAUI, a system that enables fine-grained energy-aware offload of mobile code to the infrastructure. Previous approaches to these problems either relied heavily on programmer support to partition an application, or they were coarse-grained requiring full process (or full VM) migration. MAUI uses the benefits of a managed code environment to offer the best of both worlds: it supports fine-grained code offload to maximize energy savings with minimal burden on the programmer. MAUI decides at run-time which methods should be remotely executed, driven by an optimization engine that achieves the best energy savings possible under the mobile device's current connectivity constrains. In our evaluation, we show that MAUI enables: 1) a resource-intensive face recognition application that consumes an order of magnitude less energy, 2) a latency-sensitive arcade game application that doubles its refresh rate, and 3) a voice-based language translation application that bypasses the limitations of the smartphone environment by executing unsupported components remotely.

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MAUI: making smartphones last longer with code offload

Mobile handheld devices such as PDAs and smartphones are increasingly being used by service providers to deliver application functionality similar to that found in traditional desktop computing environments. However, these handheld applications can be quite slow and often lack important functionality compared to their desktop counterparts. We have developed PASSPORT, (PDA application streaming service portal) a thin-client solution that leverages more powerful servers to run full-function desktop applications and then simply stream screen updates to the PDA for display. PASSPORT uses server-side screen scaling to provide high-fidelity display and seamless mobility across a broad range of different clients and screen sizes, including both portrait and landscape viewing modes. PASSPORT also leverages existing PDA control buttons to improve system usability and maximize available screen resolution for application display. We have implemented PASSPORT on Windows PDAs and demonstrate that it can provide superior application performance and functionality compared to the traditional approach of running applications directly on handheld devices

An Application Streaming Service for Mobile Handheld Devices

The increasing use of sensitive private data in computing is matched by a growing concern regarding data privacy. System software such as hypervisors and operating systems are supposed to protect and isolate applications and their private data, but their large codebases contain many vulnerabilities that can risk data conﬁdentiality and integrity. We introduce Realms, a new abstraction for conﬁdential computing to protect the data conﬁdentiality and integrity of virtual machines. Hardware creates and enforces Realm world, a new physical address space for Realms. Firmware controls the hardware to secure Realms and handles requests from untrusted system software to manage Realms, including creating and running them. Untrusted system software retains control of the dynamic allocation of memory to Realms, but cannot access Realm memory contents, even if run at a higher privileged level. To guarantee the security of Realms, we veriﬁed the ﬁrmware, introducing novel veriﬁcation techniques that enable us to prove, for the ﬁrst time, the security and correctness of concurrent software with hand-over-hand locking and dynamically allocated shared page tables, data races in kernel code running on relaxed memory hardware, integrated C and Arm assembly code calling one another, and untrusted software being in full control of allocating system resources. Realms are included in the Arm Conﬁdential Compute Architecture.

Design and Verification of the Arm Confidential Compute Architecture

Hypervisors are widely deployed by cloud computing providers to support virtual machines, but their growing complexity poses a security risk as large codebases contain many vulnerabilities. We have created HypSec, a new hypervisor design for retrofitting an existing commodity hypervisor using microkernel principles to reduce its trusted computing base while protecting the confidentiality and integrity of virtual machines. HypSec partitions the hypervisor into an untrusted host that performs most complex hypervisor functionality without access to virtual machine data, and a trusted core that provides access control to virtual machine data and performs basic CPU and memory virtualization. Hardware virtualization support is used to isolate and protect the trusted core and execute it at a higher privilege level so it can mediate virtual machine exceptions and protect VM data in CPU and memory. HypSec takes an end-to-end approach to securing I/O to simplify its design, with applications increasingly using secure network connections in the cloud. We have used HypSec to retrofit KVM, showing how our approach can support a widely-used full-featured hypervisor integrated with a commodity operating system. The implementation has a trusted computing base of only a few thousand lines of code, many orders of magnitude less than KVM. We show that HypSec protects the confidentiality and integrity of virtual machines running unmodified guest operating systems while only incurring modest performance overhead for real application workloads.

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Protecting Cloud Virtual Machines from Hypervisor and Host Operating System Exploits

Concurrent systems software is widely-used, complex, and error-prone, posing a significant security risk. We introduce VRM, a new framework that makes it possible for the first time to verify concurrent systems software, such as operating systems and hypervisors, on Arm relaxed memory hardware. VRM defines a set of synchronization and memory access conditions such that a program that satisfies these conditions can be mostly verified on a sequentially consistent hardware model and the proofs will automatically hold on relaxed memory hardware. VRM can be used to verify concurrent kernel code that is not data race free, including code responsible for managing shared page tables in the presence of relaxed MMU hardware. Using VRM, we verify the security guarantees of a retrofitted implementation of the Linux KVM hypervisor on Arm. For multiple versions of KVM, we prove KVM's security properties on a sequentially consistent model, then prove that KVM satisfies VRM's required program conditions such that its security proofs hold on Arm relaxed memory hardware. Our experimental results show that the retrofit and VRM conditions do not adversely affect the scalability of verified KVM, as it performs similar to unmodified KVM when concurrently running many multiprocessor virtual machines with real application workloads on Arm multiprocessor server hardware. Our work is the first machine-checked proof for concurrent systems software on Arm relaxed memory hardware.

https://dl.acm.org/doi/pdf/10.1145/3477132.3483560

Formal Verification of a Multiprocessor Hypervisor on Arm Relaxed Memory Hardware

FiST: A Systemfor StackableFile-SystemCodeGeneration

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Jason Nieh

Papers

An Application Streaming Service for Mobile Handheld Devices

Design and Verification of the Arm Confidential Compute Architecture

Protecting Cloud Virtual Machines from Hypervisor and Host Operating System Exploits

Formal Verification of a Multiprocessor Hypervisor on Arm Relaxed Memory Hardware

Fist: a system for stackable file-system code generation