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    Subject/dev/mem "unbounded?"
    Dear LKML,

    In the previous kernels, valid_phys_addr_range was not
    defined for x86, and used the static variant which
    returned 0 if access went above __pa(high_memory).

    Current behavior, though, relies on the x86 variant
    of valid_phys_addr_range, defined in arch/x86/include/asm/io.h,
    that always returns 1, hence, reading will never end since there
    won't be any condition (barring an MCE on physical hardware) that
    would say "Bad Address". Is this supposed to be by design?

    How about exposing the "top" allocated resource address from
    linux/kernel/resource.c? That way /dev/mem will know when
    all the "interesting" bits end, and can return -EFAULT for
    everything above that.

    Thanks,
    A



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