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FW: Linux-mips port: HIGHMEM Address map

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Subject: FW: Linux-mips port: HIGHMEM Address map
From: <>
Date: Tue, 8 Feb 2005 15:22:43 +0530
Original-recipient: rfc822;
Thread-index: AcUNw1P4n2z9uvr5SQuKEdUGXPtCDgAAD6Cw
Thread-topic: Linux-mips port: HIGHMEM Address map

OOPS for the previous mail I guess I goofed up a little.



Guys I am trying to figure out the virtual address map of linux mips port for the HIGHMEM enabled kernel.

I am unable to figure out from which virtual address map is the HIGHMEM Memory starts.


I found in function mem_init()


                        highstart_pfn = (KSEG1 - KSEG0) >> PAGE_SHIFT;

                        high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);


Q1.       Also I have seen in many driver source codes that virt_to_phys(high_memory) has been used, will that mean that virtual address for HIGHMEM is beginning from 0xa0000000.


If that is so then if I want to relocate it to KSEG3 which I feel will be free how can I do it?

I have my SDRAM mapped at 2 locations {virtual addresses} (0xa0000000 – 0xa3ffffff) and (0x80000000 – 0x83ffffff). Physical Address is (0x00000000 – 0x03ffffff).


I have also physical memory 0x20000000 – 0x23ffffff(physical address) to be used for HIGHMEM.


Q2.       Why is highstart_pfn reinitialized in virtual address space?





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