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    SubjectRe: [PATCH -mm -v4 1/3] i386/x86_64 boot: setup data
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    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)
    > > +{
    > > + struct page *page;
    > > + void *from;
    > > + unsigned long remain = n, offset, trunck;
    > > +
    > > + while (remain) {
    > > + page = pfn_to_page(from_phys >> PAGE_SHIFT);
    > > + from = kmap_atomic(page, KM_USER0);
    > > + offset = from_phys & ~PAGE_MASK;
    > > + if (remain > PAGE_SIZE - offset)
    > > + trunck = PAGE_SIZE - offset;
    > > + else
    > > + trunck = remain;
    > > + memcpy(to, from + offset, trunck);
    > > + kunmap_atomic(from, KM_USER0);
    > > + to += trunck;
    > > + from_phys += trunck;
    > > + remain -= trunck;
    > > + }
    > > + return 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). 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"?

    > Should it be __init?
    >
    > Care to add a line of documentation if you keep it in mm/memory.c?
    >

    OK, I will add the document in the next version.

    Best Regards,
    Huang Ying
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