Date: Fri, 5 Jan 2018 10:28:32 +0100
From: Pavel Machek <pavel@ucw.cz>
To: Tim Mouraveiko <tim.ml@ipcopper.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Bricked x86 CPU with software?
Message-ID: <20180105092831.GA7088@amd>
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Hi!

On Thu 2018-01-04 17:21:36, Tim Mouraveiko wrote:
> > On Thu 2018-01-04 14:13:56, Tim Mouraveiko wrote:
> > > > > As I mentioned before, I repeatedly and fully power-cycled the mo=
therboard and reset BIOS
> > > > > and etc. It made no difference. I can see that the processor was =
not drawing any power. The
> > > > > software code behaved in a similar fashion on other processors, u=
ntil I fixed it so that it would
> > > > > not kill any more processors.
> > > > >
> > > >
> > > > So you have code that killed more than one processor? Save it! We w=
ant
> > > > a copy.
> > > >
> > > > Do you have model numbers of affected CPUs?
> > >
> > >
> > > Why would you want a copy? Last time I checked bricked CPUs do not wo=
rk well, even as
> > > decorations.
> > >
> > > I believe the processors were Intel Xeon series. The code would likel=
y run on others too.
> >
> > Well... Intel's shares are overpriced, and you have code to fix that
> > :-).
> >
> > Actually... I don't think your code works. That's why I'm curious. But
> > if it works, its rather a big news... and I'm sure Intel and cloud
> > providers are going to be interested.
> >
>=20
> I first discovered this issue over a year ago, quite by accident. I chang=
ed the code I was
> working on so as not to kill the CPU (as that is not what I was trying to=
). We made Intel aware
> of it. They didn=B4t care much, one of their personnel suggesting that th=
ey already knew about it
> (whether this is true or not I couldn=B4t say). It popped up again later,=
 so I had to fix the code
> again. It could be a buggy implementation of a certain x86 functionality,=
 but I left it at that
> because I had better things to do with my time.
>

Is the sequence available from ring 3, or does it need ring 0?

Can we get the code? Extraordinary claims and all that...

									Pavel
--=20
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo=
g.html

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