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Date: Tue, 1 Jul 2014 10:14:13 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Andi Kleen <ak@...ux.intel.com> Cc: "HATAYAMA, Daisuke" <d.hatayama@...fujitsu.com>, hpa@...or.com, Don Zickus <dzickus@...hat.com>, matt@...sole-pimps.org, acme@...nel.org, mingo@...hat.com, paulus@...ba.org, tglx@...utronix.de, x86@...nel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2] perf/x86/intel: ignore CondChgd bit to avoid false NMI handling 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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