Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760134Ab0KRUIY (ORCPT ); Thu, 18 Nov 2010 15:08:24 -0500 Received: from mx1.redhat.com ([209.132.183.28]:1029 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755902Ab0KRUIX (ORCPT ); Thu, 18 Nov 2010 15:08:23 -0500 Date: Thu, 18 Nov 2010 15:08:07 -0500 From: Don Zickus To: Jason Wessel Cc: Peter Zijlstra , Ingo Molnar , Robert Richter , ying.huang@intel.com, Andi Kleen , LKML , Frederic Weisbecker Subject: Re: [V2 PATCH 0/6] x86, NMI: give NMI handler a face-lift Message-ID: <20101118200807.GC8131@redhat.com> References: <20101112161144.GP4823@redhat.com> <4CDD6CAD.30303@windriver.com> <20101112172755.GR4823@redhat.com> <20101116184325.GB4823@redhat.com> <4CE2E3C3.6060800@windriver.com> <20101118080516.GJ32621@elte.hu> <4CE52048.5080802@windriver.com> <1290086232.2109.1507.camel@laptop> <20101118193247.GF18100@redhat.com> <4CE583D0.8050407@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4CE583D0.8050407@windriver.com> User-Agent: Mutt/1.5.20 (2009-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1176 Lines: 27 On Thu, Nov 18, 2010 at 01:51:44PM -0600, Jason Wessel wrote: > > So the problem is when the nmi watchdog is enabled, the perf event is > > 'active' and thus tries to read the counter value. Because it is always > > zero, perf just assumes the counter overflowed and the NMI is his. > > > > Not sure how to fix it yet, other than include the logic that detects we > > are on a guest and disable perf?? > > > > > > I highly doubt we want to disable perf. I would rather use the source > and fix the nmi emulation in KVM/Qemu after we hear back the results Well I think Peter does not have a positive opinion about emulating perf inside a guest. Nor are the KVM folks having much success in doing so. Just to clarify, perf counter emulation is _not_ implemented in kvm. Therefore disabling perf in the guest makes sense until someone gets around to actually writing the emulation code for perf in a guest. :-) Cheers, Don -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/