linux-kernel - Re: [RFC PATCH] resource: Fix CXL node not populated issue

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Message-ID: <674fd2b4942f1_3e0f629420@dwillia2-mobl3.amr.corp.intel.com.notmuch>
Date: Tue, 3 Dec 2024 19:55:32 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: Raghavendra K T <raghavendra.kt@....com>, <linux-kernel@...r.kernel.org>,
	<linux-cxl@...r.kernel.org>
CC: <bharata@....com>, Raghavendra K T <raghavendra.kt@....com>, Huang Ying
	<ying.huang@...el.com>, Andrew Morton <akpm@...ux-foundation.org>, "Dan
 Williams" <dan.j.williams@...el.com>, David Hildenbrand <david@...hat.com>,
	Davidlohr Bueso <dave@...olabs.net>, Jonathan Cameron
	<jonathan.cameron@...wei.com>, Dave Jiang <dave.jiang@...el.com>, "Alison
 Schofield" <alison.schofield@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, Alistair Popple
	<apopple@...dia.com>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Baoquan He <bhe@...hat.com>,
	<ilpo.jarvinen@...ux.intel.com>, Mika Westerberg
	<mika.westerberg@...ux.intel.com>, Fontenot Nathan <Nathan.Fontenot@....com>,
	Wei Huang <wei.huang2@....com>, <regressions@...ts.linux.dev>
Subject: Re: [RFC PATCH] resource: Fix CXL node not populated issue

[ add regressions@...ts.linux.dev ]

Next time make the subject of the patch:

   Revert "resource: fix region_intersects() vs add_memory_driver_managed()"

...to make it clear that this is a revert, not a fix.

The revert should be applied if a fix does not materialize in the next few weeks.

Raghavendra K T wrote:
> Before:
> ~]$ numastat -m
> ...
>                           Node 0          Node 1           Total
>                  --------------- --------------- ---------------
> MemTotal               128096.18       128838.48       256934.65
> 
> After:
> $ numastat -m
> .....
>                           Node 0          Node 1          Node 2           Total
>                  --------------- --------------- --------------- ---------------
> MemTotal               128054.16       128880.51       129024.00       385958.67
> 
> Current patch reverts the effect of first commit where the issue is seen.

Might you be able to dig a bit further into the details like memory map
for this platform and ACPI SRAT tables? A dmesg comparison of the good
and bad cases would be useful (those can be shared via a github gist).
Even better would be some debug instrumentation to identify which call
to __region_intersects() started behaving differently resulting in a
whole node disappearing.

In terms of the urgency of fixing this it would also help to know how
prevalent the system this was found on is in the wild.