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    SubjectRe: why choose 896MB to the start point of ZONE_HIGHMEM
    On 04/06/2010 09:05 PM, Chetan Nanda wrote:
    >
    > I have a question here, what if I have a 32bit system with 2GB of RAM,
    > so in that case my 896MB - 2GB RAM would be in accessible?
    > What my understanding on the subject is:
    > Only 896 MB of physical RAM is directly mapped on to kernel 1G virtual
    > address space. And we still require page table settings to do that (page
    > table would be identity mapping). But for rest of RAM, i.e. whenever
    > there is need to access physical RAM beyond 896MB then that page will be
    > mapped on to pages from 128MB kernel virtual address space (1GB - 896MB
    > = 128MB), and AFAIK kmap is just for that.
    >
    > Please correct me if i am wrong
    >

    Correct.

    -hpa
    --
    H. Peter Anvin, Intel Open Source Technology Center
    I work for Intel. I don't speak on their behalf.



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