Messages in this thread | | | Date | Tue, 06 Apr 2010 22:28:39 -0700 | From | "H. Peter Anvin" <> | Subject | Re: why choose 896MB to the start point of ZONE_HIGHMEM |
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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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