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

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Date:   Thu, 8 Feb 2018 17:39:14 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Rolf Neugebauer <rolf.neugebauer@...ker.com>
Cc:     Borislav Petkov <bp@...en8.de>,
        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>
Subject: Re: x86/microcode/intel: Division by zero panic in 4.9.79 and 4.4.114

On Wed, Feb 07, 2018 at 04:31:59PM +0000, Rolf Neugebauer wrote:
> On Wed, Feb 7, 2018 at 2:34 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> > On Tue, Feb 06, 2018 at 03:24:44PM +0100, Borislav Petkov wrote:
> >> 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...
> >
> > It applied cleanly to 4.9 (with some fuzz, but looks clean enough...)
> >
> > But for 4.4, not at all.  Rolf, any chance you could backport the patch
> > there for this issue?  If not, I can add it to my queue, but it might
> > take a few days...
> 
> The backport was straight forward. I've added it below. If my mailer
> (gmail) screws this up let me where I should send it with 'git
> send-email'

Yeah, it's messed up, can you resend it please?

thanks,

greg k-h