This book focuses on the core question of the necessary architectural support provided by hardware to efficiently run virtual machines, and of the corresponding design of the hypervisors that run them. Virtualization is still possible when the instruction set architecture lacks such support, but the hypervisor remains more complex and must rely on additional techniques. Despite the focus on architectural support in current architectures, some historical perspective is necessary to appropriately frame the problem. The first half of the book provides the historical perspective of the theoretical framework developed four decades ago by Popek and Goldberg. It also describes earlier systems that enabled virtualization despite the lack of architectural support in hardware. As is often the case, theory defines a necessary-but not sufficient-set of features, and modern architectures are the result of the combination of the theoretical framework with insights derived from practical systems. The second half of the book describes state-of-the-art support for virtualization in both x86-64 and ARM processors. This book includes an in-depth description of the CPU, memory, and I/O virtualization of these two processor architectures, as well as case studies on the Linux/KVM, VMware, and Xen hypervisors. It concludes with a performance comparison of virtualization on current-generation x86- and ARM-based systems across multiple hypervisors.

Cloud services have revolutionized computing in the modern world. In an increasingly networked ecosystem, it is commonplace for enterprises and private parties alike to leverage cloud services for storage and compute. The most obvious benefits include scalability, increased availability, and the potential for reduced costs when compared to lower-scale on premise infrastructures. In addition, cloud-hosted data (and compute) is accessible across platforms and is not limited by geographical constraints making collaboration attractively viable. However, the benefits of outsourcing data and computation come with security and privacy concerns. This monograph explores the advances in cloud security research across both industry and academia, with a special focus on secure infrastructure, services and storage. Besides overviewing the state of the art, the monograph highlights open problems, and possible future research directions. Cloud security is a broad topic encompassing concepts from a large cross section of domains. To make this monograph concise and meaningful, several topics and challenges that are almost entirely specific to clouds are covered. For this reason, general computing security topics such as intrusion detection, software protection, phishing etc. are excluded. While these are important building blocks that need to be considered in an end-to-end cloud-centric design, they have been extensively addressed elsewhere. The publication is divided into three parts based on a broad clustering into hardware, computation, and storage. The monograph should appeal to researchers, students and professionals who work on Cloud Computing in general, and Cloud Security specifically.