linux-kernel - RE: [PATCH 3/4] ACPI/MRRM: Add "node" symlink to /sys/devices/system/memory/rangeX

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Message-ID: <SJ1PR11MB6083BF8F07A18FEF581DAAF2FCFD2@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date: Tue, 11 Feb 2025 17:02:11 +0000
From: "Luck, Tony" <tony.luck@...el.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: "Moore, Robert" <robert.moore@...el.com>, "Wysocki, Rafael J"
	<rafael.j.wysocki@...el.com>, Len Brown <lenb@...nel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"acpica-devel@...ts.linux.dev" <acpica-devel@...ts.linux.dev>, "Thomas
 Gleixner" <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "Borislav
 Petkov" <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	"x86@...nel.org" <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, "David
 Hildenbrand" <david@...hat.com>, Oscar Salvador <osalvador@...e.de>, "Danilo
 Krummrich" <dakr@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 3/4] ACPI/MRRM: Add "node" symlink to
 /sys/devices/system/memory/rangeX

>> +	if (node)
>> +		ret = sysfs_create_link(&entry->dev.kobj, &node->dev.kobj, "node");
>
> What is going to remove this symlink if the memory goes away?  Or do
> these never get removed?

There's currently no method for runtime changes to these memory ranges. They
are described by a static ACPI table.  I need to poke the folks that came up
with this to ask how memory hotplug will be handled (since CXL seems to be
making that fashionable again).

> symlinks in sysfs created like this always worry me.  What is going to
> use it?

<hand waves>User space tools that want to understand what the "per-region"
monitoring and control features are actually operating on.</hand waves>

-Tony