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Date:   Fri, 19 Mar 2021 19:10:59 +0000
From:   Sergei Trofimovich <slyfox@gentoo.org>
To:     John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc:     Valentin Schneider <valentin.schneider@arm.com>,
        linux-kernel@vger.kernel.org,
        "linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
        debian-ia64 <debian-ia64@lists.debian.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Anatoly Pugachev <matorola@gmail.com>
Subject: Re: [PATCH] ia64: Ensure proper NUMA distance and possible map
 initialization
Message-ID: <20210319191059.2a776cb8@sf>
In-Reply-To: <3c421868-d6a8-1da2-f876-49b6374270dc@physik.fu-berlin.de>
References: <20210318130617.896309-1-valentin.schneider@arm.com>
        <3c421868-d6a8-1da2-f876-49b6374270dc@physik.fu-berlin.de>
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On Fri, 19 Mar 2021 15:47:09 +0100
John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> wrote:

> 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@physik.fu-berlin.de>
> > Signed-off-by: Valentin Schneider <valentin.schneider@arm.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@physik.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?

Booted successfully without problems on rx3600.

Tested-by: Sergei Trofimovich <slyfox@gentoo.org>


-- 

  Sergei