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Message-ID: <Yv1j8v7o3lOniUoH@zn.tnic>
Date: Wed, 17 Aug 2022 23:56:02 +0200
From: Borislav Petkov <bp@...en8.de>
To: Ashok Raj <ashok.raj@...el.com>
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>
Subject: Re: [PATCH] x86/microcode/AMD: Attempt applying on every logical
thread
On Wed, Aug 17, 2022 at 08:58:07PM +0000, Ashok Raj wrote:
> For this specific patch in question, its not for testing though.. Its
> required for functional purposes?
>From its commit message:
"However, there are microcode patches which do per-thread modification,
see Link tag below.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216211"
TL;DR - the application needs to happen on *every* logical CPU.
> In effect you can test applying the same microcode over and over again
> without having any special patches.
Right now, you cannot downgrade on Zen but apparently applying the same
patch over and over again works.
The patch cache still has a version check and that prevents it but
that's ugly.
I need to test how it behaves on older families first and then think
about how to do this right. Maybe use cpuinfo_x86.microcode to record
what has been applied until now...
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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