linux-kernel - Re: [PATCH] x86/microcode/AMD: Attempt applying on every logical thread

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Date:   Wed, 17 Aug 2022 12:12:05 +0000
From:   Ashok Raj <ashok.raj@...el.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     Ashok Raj <ashok_raj@...ux.intel.com>, X86 ML <x86@...nel.org>,
        "Andrew Cooper" <amc96@...f.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Ștefan Talpalaru <stefantalpalaru@...oo.com>,
        Ashok Raj <ashok.raj@...el.com>
Subject: Re: [PATCH] x86/microcode/AMD: Attempt applying on every logical
 thread

Hi Boris

On Tue, Aug 16, 2022 at 02:41:39PM +0200, Borislav Petkov wrote:
> On Tue, Aug 16, 2022 at 09:00:14AM +0000, Ashok Raj wrote:
> > A re-application means, you want to apply even if the cpu_rev <= patch.rev
> 
> Yes.
> 
> > if cpu_rev is > patch_rev, clearly its ahead?. say BIOS has a newer
> > version than in the initrd image, do we want to replace the BIOS
> > version since we do no revid checks here.
> 
> Can you even downgrade the microcode through the MSR?
> 

Instead of doing a complete hack, could we maybe revive what we attempted
in 2019? At a minimum it will work for both architectures.

https://lore.kernel.org/lkml/1567056803-6640-1-git-send-email-ashok.raj@intel.com/

Testing microcode update is more like a unit-test and we have no luxury to
get unlimited upgraded revision numbers. But most often we might have
at least one microcode, we can play around with it, and get more results
from the community.

Back then, we just hit a wall and there was no oxygen left in the room :-)

Seems like now there is a real need for it and everyone can benefit with
something that was proposed then.

Cheers,
Ashok