linux-kernel - RE: [PATCH v2 0/6] PPIN (Protected Processor Inventory Number) updates

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Date:   Mon, 31 Jan 2022 19:29:55 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Smita Koralahalli Channabasappa 
        <smita.koralahallichannabasappa@....com>,
        Wei Huang <wei.huang2@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: RE: [PATCH v2 0/6] PPIN (Protected Processor Inventory Number)
 updates

> Lemme be clear: I'm being the devil's advocate here on purpose because
> I want to make sure we don't walk into some privacy thing we haven't
> thought about at the time.

Sure. It's good to look at this from other perspectives.  There may be some
software-as-a-service thing where the provider of the service doesn't want
a simple way to reveal that jobs are being migrated around a pool of systems.

> So I guess 0400, root:root would be the correct thing to do - admins can
> then change permissions later or so. Rather than making it readable by
> everyone by default and leaving it to people to tighten it after boot.

Yup.  If someone has a tool that needs ppin, but they don't want to run
as root they can just add either of:

	chown notrootadmin /sys/devices/system/cpu/cpu*/topology/ppin

or

	chmod 444 /sys/devices/system/cpu/cpu*/topology/ppin

to some /etc/rc* file.

-Tony