From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <ak@linux.intel.com>
Cc: "HATAYAMA, Daisuke" <d.hatayama@jp.fujitsu.com>,
hpa@zytor.com, Don Zickus <dzickus@redhat.com>,
matt@console-pimps.org, acme@kernel.org, mingo@redhat.com,
paulus@samba.org, tglx@linutronix.de, x86@kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] perf/x86/intel: ignore CondChgd bit to avoid false NMI handling
Date: Tue, 1 Jul 2014 10:14:13 +0200 [thread overview]
Message-ID: <20140701081413.GJ6758@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20140630222224.GH19781@tassilo.jf.intel.com>
On Mon, Jun 30, 2014 at 03:22:24PM -0700, Andi Kleen wrote:
> >
> > I'm also interested in the behaviour of CondChgd bit on Ivy Bridge processors.
>
> The intended meaning of CondChgd is that a hardware debugger has taken over the
> PMU. It shouldn't really be set in other circumstances.
The SDM utterly and totally fails to mention this, please fix that.
> I think right now for perf it would be best to just ignore it.
>
> In theory could stop using the PMU, but if some BIOS set it it would
> completely disable perf there. So better to just ignore it.
The even better option would be to kill off SMM mode, all that ever does
is create problems.
next prev parent reply other threads:[~2014-07-01 8:14 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-13 8:44 HATAYAMA Daisuke
2014-06-16 15:30 ` Don Zickus
2014-06-30 9:24 ` HATAYAMA, Daisuke
2014-06-30 22:22 ` Andi Kleen
2014-07-01 8:14 ` Peter Zijlstra [this message]
2014-07-01 14:22 ` Don Zickus
2014-07-02 1:07 ` HATAYAMA Daisuke
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