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In computing, a virtual machine (VM) is the virtualization or emulation of a computer system. Virtual machines are based on computer architectures and provide the functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination of the two. Virtual machines differ and are organized by their function, shown here:
VMware LLC is an American cloud computing and virtualization technology company with headquarters in Palo Alto, California. VMware was the first commercially successful company to virtualize the x86 architecture.
Xen is a free and open-source type-1 hypervisor, providing services that allow multiple computer operating systems to execute on the same computer hardware concurrently. It was originally developed by the University of Cambridge Computer Laboratory and is now being developed by the Linux Foundation with support from Intel, Citrix, Arm Ltd, Huawei, AWS, Alibaba Cloud, AMD, Bitdefender and epam.
x86 virtualization is the use of hardware-assisted virtualization capabilities on an x86/x86-64 CPU.
A hypervisor is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is called a host machine, and each virtual machine is called a guest machine. The hypervisor presents the guest operating systems with a virtual operating platform and manages the execution of the guest operating systems. Unlike an emulator, the guest executes most instructions on the native hardware. Multiple instances of a variety of operating systems may share the virtualized hardware resources: for example, Linux, Windows, and macOS instances can all run on a single physical x86 machine. This contrasts with operating-system–level virtualization, where all instances must share a single kernel, though the guest operating systems can differ in user space, such as different Linux distributions with the same kernel.
In computing, paravirtualization or para-virtualization is a virtualization technique that presents a software interface to the virtual machines which is similar, yet not identical, to the underlying hardware–software interface.
QEMU is a free and open-source emulator. It emulates a computer's processor through dynamic binary translation and provides a set of different hardware and device models for the machine, enabling it to run a variety of guest operating systems. It can interoperate with Kernel-based Virtual Machine (KVM) to run virtual machines at near-native speed. QEMU can also do emulation for user-level processes, allowing applications compiled for one architecture to run on another.
Platform virtualization software, specifically emulators and hypervisors, are software packages that emulate the whole physical computer machine, often providing multiple virtual machines on one physical platform. The table below compares basic information about platform virtualization hypervisors.
The following is a timeline of virtualization development. In computing, virtualization is the use of a computer to simulate another computer. Through virtualization, a host simulates a guest by exposing virtual hardware devices, which may be done through software or by allowing access to a physical device connected to the machine.
VMware ESXi is an enterprise-class, type-1 hypervisor developed by VMware for deploying and serving virtual computers. As a type-1 hypervisor, ESXi is not a software application that is installed on an operating system (OS); instead, it includes and integrates vital OS components, such as a kernel.
Kernel-based Virtual Machine (KVM) is a free and open-source virtualization module in the Linux kernel that allows the kernel to function as a hypervisor. It was merged into the mainline Linux kernel in version 2.6.20, which was released on February 5, 2007. KVM requires a processor with hardware virtualization extensions, such as Intel VT or AMD-V. KVM has also been ported to other operating systems such as FreeBSD and illumos in the form of loadable kernel modules.
Hardware virtualization is the virtualization of computers as complete hardware platforms, certain logical abstractions of their componentry, or only the functionality required to run various operating systems. Virtualization hides the physical characteristics of a computing platform from the users, presenting instead an abstract computing platform. At its origins, the software that controlled virtualization was called a "control program", but the terms "hypervisor" or "virtual machine monitor" became preferred over time.
Live migration, also called migration, refers to the process of moving a running virtual machine (VM) or application between different physical machines without disconnecting the client or application. Memory, storage, and network connectivity of the virtual machine are transferred from the original guest machine to the destination. The time between stopping the VM or application on the source and resuming it on destination is called 'downtime'. When the downtime of a VM during live migration is small enough that it is not noticeable by the end user, it is called a 'seamless' live migration.
libvirt is an open-source API, daemon and management tool for managing platform virtualization. It can be used to manage KVM, Xen, VMware ESXi, QEMU and other virtualization technologies. These APIs are widely used in the orchestration layer of hypervisors in the development of a cloud-based solution.
Second Level Address Translation (SLAT), also known as nested paging, is a hardware-assisted virtualization technology which makes it possible to avoid the overhead associated with software-managed shadow page tables.
GPU virtualization refers to technologies that allow the use of a GPU to accelerate graphics or GPGPU applications running on a virtual machine. GPU virtualization is used in various applications such as desktop virtualization, cloud gaming and computational science.
Hyperjacking is an attack in which a hacker takes malicious control over the hypervisor that creates the virtual environment within a virtual machine (VM) host. The point of the attack is to target the operating system that is below that of the virtual machines so that the attacker's program can run and the applications on the VMs above it will be completely oblivious to its presence.
Intel Software Guard Extensions (SGX) is a set of instruction codes implementing trusted execution environment that are built into some Intel central processing units (CPUs). They allow user-level and operating system code to define protected private regions of memory, called enclaves. SGX is designed to be useful for implementing secure remote computation, secure web browsing, and digital rights management (DRM). Other applications include concealment of proprietary algorithms and of encryption keys.
Lazy FPU state leak, also referred to as Lazy FP State Restore or LazyFP, is a security vulnerability affecting Intel Core CPUs. The vulnerability is caused by a combination of flaws in the speculative execution technology present within the affected CPUs and how certain operating systems handle context switching on the floating point unit (FPU). By exploiting this vulnerability, a local process can leak the content of the FPU registers that belong to another process. This vulnerability is related to the Spectre and Meltdown vulnerabilities that were publicly disclosed in January 2018.
Transient execution CPU vulnerabilities are vulnerabilities in a computer system in which a speculative execution optimization implemented in a microprocessor is exploited to leak secret data to an unauthorized party. The archetype is Spectre, and transient execution attacks like Spectre belong to the cache-attack category, one of several categories of side-channel attacks. Since January 2018 many different cache-attack vulnerabilities have been identified.
References
- ↑ "What is VM Escape? - The Lone Sysadmin". 22 September 2007.
- ↑ "Virtual Machines: Virtualization vs. Emulation". Archived from the original on 2014-07-15. Retrieved 2011-03-11.
- ↑ "Path Traversal vulnerability in VMware's shared folders implementation". 18 May 2016.
- ↑ Dignan, Larry. "Researcher: Critical vulnerability found in VMware's desktop apps - ZDNet". ZDNet .
- ↑ "Security Monitoring News, Analysis, Discussion, & Community". Dark Reading. Archived from the original on 2011-07-19. Retrieved 2011-10-23.
- ↑ "Black Hat ® Technical Security Conference: USA 2009 // Briefings". www.blackhat.com.
- ↑ "DEFCON 19: Virtunoid: Breaking out of KVM" (PDF). Nelson Elhage.
- ↑ "VM escape - QEMU Case Study". Mehdi Talbi & Paul Fariello.
- ↑ "VMSA-2017-0006". VMware.
- 1 2 "VMSA-2017-0018.1". VMware.
- ↑ "CVE-2018-2698". exploit-db.com: Oracle VirtualBox < 5.1.30 / < 5.2-rc1 - Guest to Host Escape. 24 January 2018.
- ↑ "Chaos Communication Congress 2019: The Great Escape of ESXi". media.ccc.de. 28 December 2019.
- ↑ "CVE-2019-18420 to 18425". Patches beheben Schwachstellen in Xen und Citrix Hypervisor.
- ↑ "CVE-2019-0964 (critical), CVE-2019-5124, CVE-2019-5146, CVE-2019-5147". Sicherheitsupdate: AMD-Treiber und VMware.
- ↑ Mantle, Mark (2020-01-28). "Sicherheitslücken in Intel-CPUs: Modifizierte Angriffe erfordern BIOS-Updates". Heise (in German). Retrieved 2024-01-10.
- ↑ "CVE-2020-3962, CVE-2020-3963, CVE-2020-3964, CVE-2020-3965, CVE-2020-3966, CVE-2020-3967, CVE-2020-3968, CVE-2020-3969, CVE-2020-3970, CVE-2020-3971". VMWare Advisory VMSA-2020-0015.1.