linux-kernel - Re: x86/microcode/intel: Division by zero panic in 4.9.79 and 4.4.114

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Message-ID: <20180206142444.7xxegyyyfwskwrxl@pd.tnic>
Date:   Tue, 6 Feb 2018 15:24:44 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Rolf Neugebauer <rolf.neugebauer@...ker.com>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     Jia Zhang <zhang.jia@...ux.alibaba.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tony Luck <tony.luck@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: x86/microcode/intel: Division by zero panic in 4.9.79 and 4.4.114

On Tue, Feb 06, 2018 at 02:09:35PM +0000, Rolf Neugebauer wrote:
> The backport of 7e702d17ed1 ("x86/microcode/intel: Extend BDW
> late-loading further with LLC size check") to 4.9.79 and 4.4.14 causes
> a division by zero panic on some single vCPU machine types on Google
> Cloud (e.g. g1-small and n1-standard-1):

The microcode loader is not supposed to load in a guest.

Greg, I guess you need something like this:

a15a753539ec ("x86/microcode/AMD: Do not load when running on a hypervisor")

I haven't tried whether it applies cleanly though...

-- 
Regards/Gruss,
    Boris.

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