Good!! Thanks a lot, Denis. 2010/12/23 Denis Kirjanov <kirjanov@gmail.com>:

On Thu, Dec 23, 2010 at 6:10 PM, Gustavo da Silva <gustavodasilva@gmail.com> wrote:

...

Hi Everyone!

Friends, could someone explain me the difference between Kernel Logical and Kernel Virtual Address?

AFAIK there are 3 types of addresses: physical, kernel virtual (one-to-one mapped), and ...user virtual addresses... Lets assume x86_32 for simplicity:

========================== +kernel part (identity-mapped) + ========================== <---- PAGE_OFFSET protection boundary +                                          + + user portion(THREAD_SIZE)+ +                                          + ========================== Kernel works on behalf of the user address space (think about that one part of the user space is always the same for each process - kernel part). Kernel portion (at PAGE_OFFSET and above) translates address using simple formula: kernel virtual addr - PAGE_OFFSET

Things are different for the bottom half of the virtual address space (THREAD_SIZE portion). This is a MMU time :) Here well-known translation process (using page tables) of the virtual address to physical one begins.

...

I'm reading Linux Device Drivers 3th, but I did not understand about that.

I have a macro vision about Kernel Virtual Address (virtual address is used do hide the paging mechanism and physical memory, I think), and Linear is the address used in to evaluate to the physical (using page directory+page table+offset).

But and the Kernel Logical Address? Why Logical Address is Virtual Address, but not all Virtual Address is a Logical Address?

Regards.

Atenciosamente,

Gustavo da Silva

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-- Regards, Denis