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 id 1ZsBwZ-000M5w-01; Fri, 30 Oct 2015 17:50:19 +0200
Subject: Re: instability of timekeeping
To: Adrian Chadd <adrian.chadd@gmail.com>
References: <56261398.60102@FreeBSD.org> <56261FE6.90302@FreeBSD.org>
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Cc: Konstantin Belousov <kostikbel@gmail.com>,
 Alexander Motin <mav@FreeBSD.org>,
 freebsd-hackers <freebsd-hackers@FreeBSD.org>,
 Poul-Henning Kamp <phk@phk.freebsd.dk>, Jung-uk Kim <jkim@FreeBSD.org>
From: Andriy Gapon <avg@FreeBSD.org>
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On 30/10/2015 15:22, Adrian Chadd wrote:
> Hm!
> 
> are you able to come up with a sane way to check whether it does C1E
> the silly way (eg that MSR on that particular platform) so we can
> print/disable it?
> 
> That way noone else has this same problem.

Well, even the silly way can work correctly.  I believe that this particular
BIOS had a bug, but there are many vendors and versions out there.
It might still make sense to print a warning.
It should be as easy as checking bit AMDK8_SMIONCMPHALT in MSR_AMDK8_IPM, see
sys/x86/x86/cpu_machdep.c.

-- 
Andriy Gapon