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

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Message-ID: <Yv1WXxcIXSQ7nMji@araj-dh-work>
Date:   Wed, 17 Aug 2022 20:58:07 +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 Wed, Aug 17, 2022 at 08:13:15PM +0200, Borislav Petkov wrote:
> > Do we have a more scalable way to support it today?
> 
> You're not reading my mails. Lemme repeat: microcode loading is a

I do read them, but probably I'm not seeing your perspective. It's
unintentional. 

> dangerous business, especially the late thing. I'm certainly not going
> to expose that to people if there's no merit. The only merit for loading
> the same revision is for testing purposes.

For this specific patch in question, its not for testing though.. Its
required for functional purposes?

> 
> If you're about to test stuff, you can just as well patch the microcode
> loader to do what you want it to, like I just did.

I guess after this patch is merged, you would need no special patches out
of tree. True? I'm sorry if I missed something that is obvious.

apply_mirocode_amd() has no revid checks, and __apply_microcode_amd() has
no revid checks.. 

In effect you can test applying the same microcode over and over again
without having any special patches. 

I thought you could enforce revid only on the primary, and siblings you
can re-apply. 

Will that will satisfy the real need?

Cheers,
Ashok