linux-kernel - RE: [Patch v3 Part2 3/9] x86/microcode/intel: Fix collect_cpu

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Message-ID: <SJ1PR11MB6083580526A7FFA11F110B77FCD09@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date:   Tue, 31 Jan 2023 17:34:14 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Borislav Petkov <bp@...en8.de>, "Raj, Ashok" <ashok.raj@...el.com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Schofield, Alison" <alison.schofield@...el.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Stefan Talpalaru <stefantalpalaru@...oo.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Jonathan Corbet <corbet@....net>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Peter Zilstra <peterz@...radead.org>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "andrew.cooper3@...rix.com" <andrew.cooper3@...rix.com>,
        "Ostrovsky, Boris" <boris.ostrovsky@...cle.com>,
        Martin Pohlack <mpohlack@...zon.de>
Subject: RE: [Patch v3 Part2 3/9] x86/microcode/intel: Fix collect_cpu_info()
 to reflect current microcode

>> Currently collect_cpu_info() is only returning what was cached earlier
>> instead of reading the current revision from the proper MSR.
>
> Because this is how this is supposed to work: you collect what's
> currently applied - which should be exactly the same as what's in the
> MSR - and then see if there's a new patch in the cache and if so, update
> it.

But those get out of step when applying ucode on one logical CPU does
an update to other(s) (in this case the HT sibling for the same core).

Would you prefer that Ashok leave collect_cpu_info() as-is, and create
a new function to read the MSR?

-Tony