-----Original Message----- From: kernelnewbies-bounce@xxxxxxxxxxxx [mailto:kernelnewbies-bounce@xxxxxxxxxxxx]On Behalf Of P.F. Tsai >the first 3GB in VA is left for process itself, and the fourth gigabyte is >left for kernel. >during the kernel booting, va from PAGE_OFFSET was DIRECTLY mapped to pa >from 0 and thats why we subtract PAGE_OFFSET. but that was constrained for >RAM size belows 896 MB. >I am instrested in how it works in the case of RAM size larger than 896 MB >(and less than 4GB)? ram window? >could anyone give me a detail about it ? Memory above 896 MB is considered to be HIGH_MEM. If you have a machine with more than 896MB and want to use the HIGH_MEM then you need to call the page allocation function with GFP_HIGHMEM and then use "kmap" to get a kernel mode virtual address for that page. -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
