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    SubjectRe: [PATCH -mm -v4 1/3] i386/x86_64 boot: setup data
    Date
    On Tuesday 09 October 2007 18:22, Huang, Ying wrote:
    > On Tue, 2007-10-09 at 01:25 +1000, Nick Piggin wrote:
    > > On Tuesday 09 October 2007 16:40, Huang, Ying wrote:
    > > > +unsigned long copy_from_phys(void *to, unsigned long from_phys,
    > > > + unsigned long n)

    > > I suppose that's not unreasonable to put in mm/memory.c, although
    > > it's not really considered a problem to do this kind of stuff in
    > > a low level arch file...
    > >
    > > You have no kernel virtual mapping for the source data?
    >
    > On 32-bit platform such as i386. Some memory zones have no kernel
    > virtual mapping (highmem region etc).

    I'm just wondering whether you really need to access highmem in
    boot code...


    > So I think this may be useful as a
    > universal way to access physical memory. But it can be more efficient to
    > implement it in arch file for some arch. Should this implementation be
    > used as a fall back implementation with attribute "weak"?

    Definitely on most architectures it would just amount to
    memcpy(dst, __va(phys), n);, right? However I don't know if
    it's worth the trouble of overriding it unless there is some
    non-__init user of it.
    -
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