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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20230816215854.GWZN1GniMWRL0GnyVh@fat_crate.local>
Date:   Wed, 16 Aug 2023 23:58:54 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Jim Mattson <jmattson@...gle.com>
Cc:     dave.hansen@...el.com, linux-kernel@...r.kernel.org,
        stable@...nel.org, x86@...nel.org
Subject: Re: [PATCH 1/2] x86/microcode/AMD: Load late on both threads too

On Wed, Aug 16, 2023 at 02:36:57PM -0700, Jim Mattson wrote:
> Doesn't this render that attestation misleading, since the microcode
> patch may not have been loaded on all logical processors?

For that it doesn't matter because the microcode engine is shared
between the two threads. The updated microcode revision is shown on any
of the two threads so you can load on one only. And we did this for
years.

Only recently we started loading on both and we will be doing that from
now on.

What could be problematic is if it simply fails loading on some cores
- regardless of SMT - but that would be problematic not only to SEV-SNP
attestation but to the general system health. tglx has some patches
which verify what has been successfully loaded where so hopefully we'll
be verifying more in that area.

HTH.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette