From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: perf uncore & lkvm woes Date: Tue, 21 Aug 2012 11:34:47 +0300 Message-ID: <50334827.6010906@redhat.com> References: <1345101585.31459.112.camel@twins> <502CA368.8050404@linux.intel.com> <502CB1F6.4010204@redhat.com> <502CD444.5020807@redhat.com> <1345115846.29668.16.camel@twins> <502CD891.5030102@redhat.com> <502DA115.1090907@linux.intel.com> <1345186574.29668.56.camel@twins> <5030B82C.5000106@redhat.com> <1345533096.23018.83.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Yan, Zheng" , Pekka Enberg , Sasha Levin , Asias He , Cyrill Gorcunov , Ingo Molnar , KVM General , Gleb Natapov To: Peter Zijlstra Return-path: Received: from mx1.redhat.com ([209.132.183.28]:39177 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754453Ab2HUIf2 (ORCPT ); Tue, 21 Aug 2012 04:35:28 -0400 In-Reply-To: <1345533096.23018.83.camel@twins> Sender: kvm-owner@vger.kernel.org List-ID: On 08/21/2012 10:11 AM, Peter Zijlstra wrote: > On Sun, 2012-08-19 at 12:55 +0300, Avi Kivity wrote: >> > I think Avi prefers the method where KVM 'fakes' the MSRs and we have to >> > detect if the MSRs actually work or not. >> >> s/we have/we don't have/. > > So for the 'normal' PMU we actually do check to see if the MSRs are > being faked and bail if they are. That was because earlier versions of kvm did not virtualize the pmu. The approaches are not mutually exclusive. We can check in the guest, and fake it in the host. The problem with faking it in the host is if someone actually relies on the pmu for something, not just instrumentation. We do that for the watchdog, but I don't see it happening with the uncore pmu. -- error compiling committee.c: too many arguments to function