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Message-Id: <20210324115432.4102cd93d35a2edb1742dec7@linux-foundation.org>
Date: Wed, 24 Mar 2021 11:54:32 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Valentin Schneider <valentin.schneider@....com>
Cc: linux-kernel@...r.kernel.org,
"linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
debian-ia64 <debian-ia64@...ts.debian.org>,
John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Sergei Trofimovich <slyfox@...too.org>,
Anatoly Pugachev <matorola@...il.com>
Subject: Re: [PATCH] ia64: Ensure proper NUMA distance and possible map
initialization
On Thu, 18 Mar 2021 13:06:17 +0000 Valentin Schneider <valentin.schneider@....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.
>
> Link: http://lore.kernel.org/r/255d6b5d-194e-eb0e-ecdd-97477a534441@physik.fu-berlin.de
> Fixes: 620a6dc40754 ("sched/topology: Make sched_init_numa() use a set for the deduplicating sort")
> Reported-by: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
> Signed-off-by: Valentin Schneider <valentin.schneider@....com>
> ---
> This might need an earlier Fixes: tag, but all of this is quite old and
> dusty (the git blame rabbit hole leads me to ~2008/2007)
>
Thanks. Is this worth a cc:stable tag?
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