linux-kernel - Re: [PATCH] mm, x86: Skip NUMA_NO

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Date:	Fri, 06 Dec 2013 07:52:16 -0700
From:	Toshi Kani <toshi.kani@...com>
To:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
Cc:	akpm@...ux-foundation.org, mingo@...nel.org, hpa@...or.com,
	tglx@...utronix.de, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] mm, x86: Skip NUMA_NO_NODE while parsing SLIT

On Fri, 2013-12-06 at 16:23 +0900, Yasuaki Ishimatsu wrote:
> (2013/12/06 0:11), Toshi Kani wrote:
> > On Thu, 2013-12-05 at 19:25 +0900, Yasuaki Ishimatsu wrote:
> >> (2013/12/05 6:09), Toshi Kani wrote:
> >>> When ACPI SLIT table has an I/O locality (i.e. a locality unique
> >>> to an I/O device), numa_set_distance() emits the warning message
> >>> below.
> >>>
> >>>    NUMA: Warning: node ids are out of bound, from=-1 to=-1 distance=10
> >>>
> >>> acpi_numa_slit_init() calls numa_set_distance() with pxm_to_node(),
> >>> which assumes that all localities have been parsed with SRAT previously.
> >>> SRAT does not list I/O localities, where as SLIT lists all localities
> >>
> >>> including I/Os.  Hence, pxm_to_node() returns NUMA_NO_NODE (-1) for
> >>> an I/O locality.  I/O localities are not supported and are ignored
> >>> today, but emitting such warning message leads unnecessary confusion.
> >>
> >> In this case, the warning message should not be shown. But if SLIT table
> >> is really broken, the message should be shown. Your patch seems to not care
> >> for second case.
> >
> > In the second case, I assume you are worrying about the case of SLIT
> > table with bad locality numbers.  Since SLIT is a matrix of the number
> > of localities, it is only possible by making the table bigger than
> > necessary.  Such excessive localities are safe to ignore (as they are
> > ignored today) and regular users have nothing to concern about them.
> > The warning message in this case may be helpful for platform vendors to
> > test their firmware, but they have plenty of other methods to verify
> > their SLIT table.
> 
> I understood it. So,
> 
> Reviewed-by : Yasuaki Ishimatsu

Great.  Thanks Yasuaki!
-Toshi


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