Two Level Page Table

[Dhinesh]

We know that page table Directory base address is stored in cr3 register . But how does a entry in page table directory know where to find the corresponding page table entry? I know that it uses first 20 bit to find the address of the page table. But where it gets the base address of the page table ?

Thanks & Regards,

Dhinesh L

[Dhinesh]

So, the page directory provides the base which is 20 bit, and the offset is present in the linear address (next 10 bit). Since each entry is 4 byte(32 bit) . We dont need the last 2 bits. 

[Arsh Gautam]

Virtual address, va is 32 bits. The first 10 bits of va index into the page table directory. The entry of page table directory is 32 bits, of which 20 bits is used to address the page table entry and next 10 bits from va are used to index the page table page. Now 20 bits of page table entry point to actual pages while the next 12 bits of virtual address byte address in the page.