windows 虛拟位址映射到實體位址

1. The CPU’s MMU locates the page directory for the process using

the special register mentioned above.

2. The page directory index (from the first 10 bits of the virtual address)

is used to locate the PDE that identifies the page table

needed to map the virtual address to a physical one.

3. The page table index (from the second 10 bits of the virtual address)

is used to locate the PTE that maps the physical location of the virtual

memory page referenced by the address.

4. The PTE is used to locate the physical page. If the virtual page is

mapped to a page that is already in physical memory, the PTE will

contain the page frame number (PFN) of the page in physical memory

that contains the data in question. (Processors reference memory

locations by PFN.) If the page is not in physical memory, the MMU

raises a page fault, and the Windows page fault–handling code attempts

to locate the page in the system paging file. If the page can be

located, it is loaded into physical memory, and the PTE is updated to

reflect its location. If it cannot be located and the translation is a user

mode translation, an access violation occurs because the virtual address

references an invalid physical address. If the page cannot be

located and the translation is occurring in kernel mode, a bug check

(also called a blue screen) occurs.