linux-kernel - Re: [PATCH 1/2] x86/microcode/AMD: Load late on both threads too

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Message-ID: <20230816201700.589822-1-jmattson@google.com>
Date:   Wed, 16 Aug 2023 13:17:00 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     dave.hansen@...el.com
Cc:     bp@...en8.de, linux-kernel@...r.kernel.org, stable@...nel.org,
        x86@...nel.org, Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH 1/2] x86/microcode/AMD: Load late on both threads too

On Wed, Jun 07, 2023 at 13:15:42 -0700, Dave Hansen wrote:
>On 6/7/23 13:03, Borislav Petkov wrote:
>> On Wed, Jun 07, 2023 at 12:36:53PM -0700, Dave Hansen wrote:
>>> What's the benefit of doing the loading on both threads?  I would have
>>> naively thought it was just wasted work.
>> I have the perfect example for this, see:
>> 
>> e7ad18d1169c ("x86/microcode/AMD: Apply the patch early on every logical thread")
>> 
>> so it is for reasons like that.
>
>Yikes, so the second CMT thread reports a bumped version but not all the
>_effects_ of that version?  That's, uh ... fun???

That does seem like fun. :)

Borislav,

Is there any way to tell that a microcode patch has been loaded on only one
thread? And what does this mean for SEV-SNP attestation?