----------------------------------------
>> On 18-11-07 20:08, Talib Alim wrote:
>>>
>>> I use following expression to get virtual address and copy data
>>>
>>> virtual_address = phys_to_virt(page_to_pfn(page) << PAGE_SHIFT);
>>>
>>> This works fine on Pentium III machine with 515324 KB memory, but when
>>> I run same code on Xeon with 2074604 KB memory, I get
>
> Your virtual_address= only works for lowmem, the permanently and 1:1 mapped
> portion of physical memory. With the standard 3:1 user/kernel split, there's
> room for at most 896M of that. Your P3 will therefore have all its 512M as
> lowmem, but the 2G Xeon will (probably I should say, check your dmesg) be
> using most of it as highmem.
>
> You should look into kmap{,_atomic}() to map highmem.
Thanks.
So, if virtual_address retuned is in 0xdxxxxxxx than I can assume this is mapped, otherwise I map it ? is this correct.
Also, can somebody explain what page_to_pfn does and why << PAGE_SHIFT is needed ?
(For my better understanding. page_to_pfn is adding some constant, what is the significance and what pfn stands for)
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