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    SubjectRe: [PATCH] percpu data: only iterate over possible CPUs
    > > > powerpc/ppc64, for instance, determines the number of possible cpus
    > > > from information exported by firmware (and I'm mystified as to why
    > > > other platforms don't do this). So it's typical to have a kernel an a
    > > > pSeries partition with NR_CPUS=128, but cpu_possible_map = 0xff.
    > >
    > > Simply because there is no such interface on s390. The only thing we know
    > > for sure is that if we are running under z/VM the user is free to
    > > configure up to 63 additional virtual cpus on the fly...
    >
    > x86-64 had the same problem, but we now require that you
    > boot with additional_cpus=... for how many you want. Default is 0
    > (used to be half available CPUs but that lead to confusion)

    So introducing the additional_cpus kernel parameter seems to be the way
    to go (for XEN probably too). Even though it seems to be a bit odd if the
    user specifies both maxcpus=... and additional_cpus=...

    Heiko
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