Hello, On more question. The second example:
>> ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for >> hypervisor What are the relation between the Bits (=43bits) and the Adresse Range ? Is it possible to calculate the 43 Bits from the range ? If yes, how ? Best regards Damian > Am 13.12.2017 um 05:35 schrieb arshad hussain <[email protected]>: > > On Wed, Dec 13, 2017 at 12:44 AM, Damian Tometzki > <[email protected]> wrote: >> Hello all, >> >> i have a short question: >> >> How are the bits (in brackets) calculated in the virtual memory map ? >> >> for example the first line (=47 bits) >> >> Virtual memory map with 4 level page tables: >> >> 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm >> hole caused by [47:63] sign extension >> ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for >> hypervisor >> > > Presently for x86-64 kernel uses 4-level paging. Out of 64bit only 48 bit > is enabled (Which boils down to Terabyte of address space). For case > where getpagesize() is 4K the breakup is :- > > CR3 -> Global(9 bits) -> Upper(9 bits) -> Middle(9 bits) -> Page > table(9 bits) -> [12 bits for page or 4096 bytes] = (48 bits) > > Thanks
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