On Jan 11, 2008 11:45 AM, sahlot arvind <asahlot@xxxxxxxxx> wrote:
yes thats right.
Thanks for your response!
What is PAGE_OFFSET at 3GB on x86,?
Kernel memory is defined to start at PAGE_OFFSET. (This is where the 3gig/1gig split is
defined.) Every virtual address above PAGE_OFFSET is the kernel, any
address below PAGE_OFFSET is a user address.
As you said PA to VA is found by subtracting PAGE_OFFSET, that means it is not likePA = VA. Right?
yes thats right.
On 1/11/08, Mahaveer Darade <mah.darade@xxxxxxxxx> wrote:
On Jan 11, 2008 10:57 AM, sahlot arvind <asahlot@xxxxxxxxx> wrote:
Hi All,I just started learning Linux Virtual Memory Management Subsystem.I see the memory is divided into three zones. Comments in file mm/mmzone.h/** ZONE_DMA < 16 MB ISA DMA capable memory
* ZONE_NORMAL 16-896 MB direct mapped by the kernel
* ZONE_HIGHMEM > 896 MB only page cache and user processes
*/
Here second comment (ZONE_NORMAL) says that it is directly mapped by kernel.Could anybody please tell me what does direct mean here?Does this mean Physical address = Virtual Address???
yes, thats right.
This means any virtual address can be translated to the physical address by simply subtracting PAGE_OFFSET at 3GB on x86, which is essentially what the function virt_to_phys() with the macro __pa() does.
Thanks- Arvind
--
---------------------------
Thanks & Regards,
Mahaveer Darade
mah.darade@xxxxxxxxx
Mobile - 9970365267
--- Dream it , Code it.
---The "silly question" is the first intimation of some totally new development
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---------------------------
Thanks & Regards,
Mahaveer Darade
mah.darade@xxxxxxxxx
Mobile - 9970365267
--- Dream it , Code it.
---The "silly question" is the first intimation of some totally new development
