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

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Date:   Fri, 19 Mar 2021 15:47:09 +0100
From:   John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To:     Valentin Schneider <valentin.schneider@....com>,
        linux-kernel@...r.kernel.org,
        "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
        debian-ia64 <debian-ia64@...ts.debian.org>
Cc:     "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

Hi Valentin!

On 3/18/21 2:06 PM, Valentin Schneider 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)
> 
> Alternatively, can we deprecate ia64 already?
> ---
>  arch/ia64/kernel/acpi.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/ia64/kernel/acpi.c b/arch/ia64/kernel/acpi.c
> index a5636524af76..e2af6b172200 100644
> --- a/arch/ia64/kernel/acpi.c
> +++ b/arch/ia64/kernel/acpi.c
> @@ -446,7 +446,8 @@ void __init acpi_numa_fixup(void)
>  	if (srat_num_cpus == 0) {
>  		node_set_online(0);
>  		node_cpuid[0].phys_id = hard_smp_processor_id();
> -		return;
> +		slit_distance(0, 0) = LOCAL_DISTANCE;
> +		goto out;
>  	}
>  
>  	/*
> @@ -489,7 +490,7 @@ void __init acpi_numa_fixup(void)
>  			for (j = 0; j < MAX_NUMNODES; j++)
>  				slit_distance(i, j) = i == j ?
>  					LOCAL_DISTANCE : REMOTE_DISTANCE;
> -		return;
> +		goto out;
>  	}
>  
>  	memset(numa_slit, -1, sizeof(numa_slit));
> @@ -514,6 +515,8 @@ void __init acpi_numa_fixup(void)
>  		printk("\n");
>  	}
>  #endif
> +out:
> +	node_possible_map = node_online_map;
>  }
>  #endif				/* CONFIG_ACPI_NUMA */
>  
> 

Tested-by: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>

Could you send this patch through Andrew Morton's tree? The ia64 port currently
has no maintainer, so we have to use an alternative tree.

@Sergei: Could you test/ack this patch as well?

Thanks,
Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@...ian.org
`. `'   Freie Universitaet Berlin - glaubitz@...sik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913