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Intel 5-level paging, referred to simply as 5-level paging in Intel documents, is a processor extension for the x86-64 line of processors. [ 1 ] : 11 It extends the size of virtual addresses from 48 bits to 57 bits by adding an additional level to x86-64's multilevel page tables , increasing the addressable virtual memory from 256 TiB to 128 PiB .
For some processors, a mode can be enabled with a fifth table, the 512-entry page-map level 5 table; this means that 57 bits of virtual page number are translated, giving a virtual address space of up to 128 PB. [10]: 141–153 In the page table entries, in the original specification, 40 bits of physical page number are implemented.
In computing, a page fault is an exception that the memory management unit (MMU) raises when a process accesses a memory page without proper preparations. Accessing the page requires a mapping to be added to the process's virtual address space. Furthermore, the actual page contents may need to be loaded from a back-up, e.g. a disk.
It is also helpful to use large pages in the host page tables to reduce the number of levels (e.g., in x86-64, using 2 MB pages removes one level in the page table). Since memory is typically allocated to virtual machines at coarse granularity, using large pages for guest-physical translation is an obvious optimization, reducing the depth of ...
See Intel 64 and IA-32 Architectures Software Developer's Manual. 23: CET: Control-flow Enforcement Technology: If set, enables control-flow enforcement technology. [16]: 2–19 24: PKS: Enable Protection Keys for Supervisor-Mode Pages: If set, each supervisor-mode linear address is associated with a protection key when 4-level or 5-level ...
In computing, protected mode, also called protected virtual address mode, [1] is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as segmentation, virtual memory, paging and safe multi-tasking designed to increase an operating system's control over application software.
It is only available with the long mode (64-bit mode) or legacy Physical Address Extension (PAE) page-table formats, but not x86's original 32-bit page table format because page table entries in that format lack the 64th bit used to disable and enable execution. Windows XP SP2 and later support Data Execution Prevention (DEP).
The page-directory entry with PS set to 0 behaves as without PSE. If newer PSE-36 capability is available on the CPU, as checked using the CPUID instruction, then 4 more bits, in addition to normal 10 bits, are used inside a page-directory entry pointing to a large page. This allows a large page to be located in 36-bit address space.