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    SubjectRe: [PATCH v6] numa: make node_to_cpumask_map() NUMA_NO_NODE aware
    On Mon 23-09-19 22:34:10, Peter Zijlstra wrote:
    > On Mon, Sep 23, 2019 at 06:52:35PM +0200, Michal Hocko wrote:
    [...]
    > > I even the
    > > ACPI standard is considering this optional. Yunsheng Lin has referred to
    > > the specific part of the standard in one of the earlier discussions.
    > > Trying to guess the node affinity is worse than providing all CPUs IMHO.
    >
    > I'm saying the ACPI standard is wrong.

    Even if you were right on this the reality is that a HW is likely to
    follow that standard and we cannot rule out NUMA_NO_NODE being
    specified. As of now we would access beyond the defined array and that
    is clearly a bug.

    Let's assume that this is really a bug for a moment. What are you going
    to do about that? BUG_ON? I do not really see any solution besides to either
    provide something sensible or BUG_ON. If you are worried about a
    conditional then this should be pretty easy to solve by starting the
    array at -1 index and associate it with the online cpu mask.
    --
    Michal Hocko
    SUSE Labs

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