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    SubjectRe: MCE, AMD: Hide smp-only code around CONFIG_SMP
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    On 9 February 2012 04:06, Ingo Molnar <mingo@elte.hu> wrote:
    >
    > * Borislav Petkov <bp@alien8.de> wrote:
    >
    >> +++ b/arch/x86/include/asm/smp.h
    >> @@ -33,8 +33,15 @@ static inline bool cpu_has_ht_siblings(void)
    >>
    >>  DECLARE_PER_CPU(cpumask_var_t, cpu_sibling_map);
    >>  DECLARE_PER_CPU(cpumask_var_t, cpu_core_map);
    >> -/* cpus sharing the last level cache: */
    >> +
    >> +#ifdef CONFIG_SMP
    >> +/* CPUs sharing the last level cache: */
    >>  DECLARE_PER_CPU(cpumask_var_t, cpu_llc_shared_map);
    >> +#else
    >> +static DECLARE_BITMAP(cpu_llc_shared_bits, NR_CPUS) __read_mostly = { [0] = 1UL };
    >> +static struct cpumask *const cpu_llc_shared_map = to_cpumask(cpu_llc_shared_bits);
    >> +#endif
    >
    > Why not just expose it like on SMP?
    >
    > We want to *reduce* the specialness of UP, not increase it - one
    > more word of .data and .text does not matter much - UP is
    > becoming more and more an oddball, rarely tested config. By the
    > time these changes hit any real boxes it will be even more
    > oddball.
    >

    It seems that cpu_llc_shared_map is actually defined in
    arch/x86/kernel/smpboot.c, which is not compiled/linked for UP builds.
    Is there an equivalent file for UP that could be used instead, or
    could the:

    DEFINE_PER_CPU(cpumask_var_t, cpu_llc_shared_map);

    be moved to some other file?

    Generally, it sounds like you might approve of an eventual merging of
    the boot paths for SMP and UP. Is that true? I wonder how much work
    that would be. That would really reduce the specialness of UP.

    --
    Kevin Winchester
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