Re: [PATCH] ia64: Ensure proper NUMA distance and possible map initialization

On Thu, 18 Mar 2021 13:06:17 +0000 Valentin Schneider <valentin.schneider@arm.com> wrote:

> John Paul reported a warning about bogus NUMA distance values spurred by
> commit:
>
>   620a6dc40754 ("sched/topology: Make sched_init_numa() use a set for the deduplicating sort")
>
> In this case, the afflicted machine comes up with a reported 256 possible
> nodes, all of which are 0 distance away from one another. This was
> previously silently ignored, but is now caught by the aforementioned
> commit.
>
> The culprit is ia64's node_possible_map which remains unchanged from its
> initialization value of NODE_MASK_ALL. In John's case, the machine doesn't
> have any SRAT nor SLIT table, but AIUI the possible map remains untouched
> regardless of what ACPI tables end up being parsed. Thus, !online &&
> possible nodes remain with a bogus distance of 0 (distances \in [0, 9] are
> "reserved and have no meaning" as per the ACPI spec).
>
> Follow x86 / drivers/base/arch_numa's example and set the possible map to
> the parsed map, which in this case seems to be the online map.
>