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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.
A hardware page table walker can treat the additional translation layer almost like adding levels to the page table. Using SLAT and multilevel page tables, the number of levels needed to be walked to find the translation doubles when the guest-physical address is the same size as the guest-virtual address and the same size pages are used.
Below is the full 8086/8088 instruction set of Intel (81 instructions total). [2] These instructions are also available in 32-bit mode, in which they operate on 32-bit registers (eax, ebx, etc.) and values instead of their 16-bit (ax, bx, etc.) counterparts.
The multilevel page table may keep a few of the smaller page tables to cover just the top and bottom parts of memory and create new ones only when strictly necessary. Now, each of these smaller page tables are linked together by a master page table, effectively creating a tree data structure. There need not be only two levels, but possibly ...
Supporting 64 bit addresses in the page-table is a significant change as this enables two changes to the processor addressing. Firstly, the page table walker, which uses physical addresses to access the page table and directory, can now access physical addresses greater than the 32-bit physical addresses supported in systems without PAE.
The page attribute table (PAT) is a processor supplementary capability extension to the page table format of certain x86 and x86-64 microprocessors. Like memory type range registers (MTRRs), they allow for fine-grained control over how areas of memory are cached , and are a companion feature to the MTRRs.
If it is a TLB miss, then the CPU checks the page table for the page table entry. If the present bit is set, then the page is in main memory, and the processor can retrieve the frame number from the page-table entry to form the physical address. [6] The processor also updates the TLB to include the new page-table entry.
These instructions were introduced in 6th generation Intel Core "Skylake" CPUs. The last CPU generation to support them was the 9th generation Core "Coffee Lake" CPUs. Intel MPX adds 4 new registers, BND0 to BND3, that each contains a pair of addresses.