From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752030Ab2GLE3a (ORCPT ); Thu, 12 Jul 2012 00:29:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:62067 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750958Ab2GLE33 (ORCPT ); Thu, 12 Jul 2012 00:29:29 -0400 Date: Thu, 12 Jul 2012 07:29:23 +0300 From: Gleb Natapov To: David Ahern Cc: Peter Zijlstra , Avi Kivity , LKML Subject: Re: perf with precise attribute kills all KVM based VMs Message-ID: <20120712042923.GG7298@redhat.com> References: <4FFAED16.7050204@redhat.com> <4FFAEF13.7010108@gmail.com> <1341845396.3462.81.camel@twins> <4FFAEFF1.9000706@redhat.com> <1341845999.3462.86.camel@twins> <4FFCBD00.1030109@gmail.com> <20120711071006.GF23898@redhat.com> <1342000187.3462.134.camel@twins> <20120711095337.GJ23898@redhat.com> <4FFE4E8D.90606@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4FFE4E8D.90606@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 11, 2012 at 10:11:57PM -0600, David Ahern wrote: > On 7/11/12 3:53 AM, Gleb Natapov wrote: > >On Wed, Jul 11, 2012 at 11:49:47AM +0200, Peter Zijlstra wrote: > >>On Wed, 2012-07-11 at 10:10 +0300, Gleb Natapov wrote: > >> > >>>Looks like Avi is right about the overshoot. Can you test something like this? > >>> > >>>diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c > >>>index 166546e..5fb371a 100644 > >>>--- a/arch/x86/kernel/cpu/perf_event_intel.c > >>>+++ b/arch/x86/kernel/cpu/perf_event_intel.c > >>>@@ -1374,8 +1374,11 @@ static struct perf_guest_switch_msr *intel_guest_get_msrs(int *nr) > >>> arr[0].msr = MSR_CORE_PERF_GLOBAL_CTRL; > >>> arr[0].host = x86_pmu.intel_ctrl & ~cpuc->intel_ctrl_guest_mask; > >>> arr[0].guest = x86_pmu.intel_ctrl & ~cpuc->intel_ctrl_host_mask; > >>>+ arr[1].msr = MSR_IA32_PEBS_ENABLE; > >>>+ arr[1].host = cpuc->pebs_enabled; > >>>+ arr[1].guest = 0; > >>>+ *nr = 2; > >>> > >>>- *nr = 1; > >>> return arr; > >>> } > >> > > So far the 64-bit Fedora 10 VM with both a Fedora 10 stock kernel > and a 2.6.38 kernel have not faired well - and that's the only VM I > have tried at the moment. Using -e cycles:pp I have been able to > lock up the VM 3 times out of 3 series of tests with perf-kvm that > includes network traffic (e.g., netperf), disk I/O (dd based to > create a file with dsync flag) and pure userspace cpu bound (openssl > speed). May or may not be related. > OK that's may be BTSes. What about -e cycles:p? BTW are you using your patch to set exclude_guest parameter? If not use -e cycles:Hp. > Also, I noted that 'perf kvm --guest record -e cycles:pp' does not > generate a whole lot of samples -- like < 100 in a 20-second sample > -- despite the fact that the guest is rather busy. > Host events do not suppose to generate events while guest is running. > I won't have much time over the next few days to run much in the way > of tests; I'll come back to it Sunday night. > > David > > >> > >>You also need to clear TR, BTS, BTINT from MSR_IA32_DEBUGCTLMSR and > >>ideally you'd also clear MSR_IA32_DS_AREA so that any write will be a > >>proper NULL deref or such. > >Yes. With the patch above :pp modifier does not crash guest for me, but > >in theory it should since BTS are still written to DS. May be BTS writes do > >not overshoot guest entry. Will have to ask Intel for clarification. -- Gleb.