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x86 virtualization is the use of hardware-assisted virtualization capabilities on an x86/x86-64 CPU.. In the late 1990s x86 virtualization was achieved by complex software techniques, necessary to compensate for the processor's lack of hardware-assisted virtualization capabilities while attaining reasonable performance.
In virtualization, guest operating systems can use hardware that is not specifically made for virtualization. Higher performance hardware such as graphics cards use DMA to access memory directly; in a virtual environment all memory addresses are re-mapped by the virtual machine software, which causes DMA devices to fail.
System Management Mode (SMM, sometimes called ring −2 in reference to protection rings) [1] [2] is an operating mode of x86 central processor units (CPUs) in which all normal execution, including the operating system, is suspended.
There, both components form the overall virtualization stack of a certain system. Hypervisor refers to kernel-space functionality and VMM to user-space functionality. Specifically in these contexts, a hypervisor is a microkernel implementing virtualization infrastructure that must run in kernel-space for technical reasons, such as Intel VMX.
KVM (Kernel-based Virtual Machine) is a FreeBSD and Linux kernel module that allows a user space program access to the hardware virtualization features of various processors, with which QEMU can offer virtualization for x86, PowerPC, and S/390 guests. When the target architecture is the same as the host architecture, QEMU can make use of KVM ...
Full virtualization – Almost complete virtualization of the actual hardware to allow software environments, including a guest operating system and its apps, to run unmodified. Paravirtualization – The guest apps are executed in their own isolated domains, as if they are running on a separate system, but a hardware environment is not simulated.
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 emulates the hardware environment of its host architecture, allowing multiple OSes to run unmodified and in isolation.
UEFI replaces the BIOS that was present in the boot ROM of all personal computers that are IBM PC compatible, [5] [6] although it can provide backwards compatibility with the BIOS using CSM booting. Unlike its predecessor, BIOS, which is a de facto standard originally created by IBM as proprietary software, UEFI is an open standard maintained ...