From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752464Ab2LXKgq (ORCPT ); Mon, 24 Dec 2012 05:36:46 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48992 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751678Ab2LXKgm (ORCPT ); Mon, 24 Dec 2012 05:36:42 -0500 Date: Mon, 24 Dec 2012 12:36:20 +0200 From: Gleb Natapov To: David Ahern Cc: Linus Torvalds , Ingo Molnar , Linux Kernel Mailing List , Arnaldo Carvalho de Melo , Peter Zijlstra , Thomas Gleixner , Andrew Morton Subject: Re: [GIT PULL] perf changes for v3.8 Message-ID: <20121224103620.GU17584@redhat.com> References: <20121211090910.GA22985@gmail.com> <50C94A9C.2050900@gmail.com> <50C94ECD.6020504@gmail.com> <20121217102000.GE11016@redhat.com> <50D60A5B.1020700@gmail.com> <20121223092324.GN17584@redhat.com> <50D79119.9010002@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50D79119.9010002@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Dec 23, 2012 at 04:17:45PM -0700, David Ahern wrote: > On 12/23/12 2:23 AM, Gleb Natapov wrote: > >>Your patch alone was not enough. Start here: > >> https://lkml.org/lkml/2012/7/12/3 > >> > >I cannot reproduce this failure. I reverted 20b279ddb38c and ran "perf > >record -e cycles:ppG" while guest was running. Admittedly I ran the test > >for a short time, but without disabling PEBS during the guest entry this > >was enough to crash a guest. > > In the beginning (without any patches) VMs crashed fairly quickly. > With your patch it took longer, but I was able to consistently crash > VMs. The thread notes server info (processor, OS) and VM versions as > well as load used for the tests -- a cpu bound process (openssl), > disk bound (dd) and network (netperf). > > It means that disabling PEBS is not enough and PMU counter should be disabled too. > >What about forcing exclude_guest on an event that > >has precise flag set without reporting error to userspace? > > That's up to the perf maintainers -- Ingo, Peter, Arnaldo. > Personally, I don't like it since kernel side is changing the user > request. > I do not see other way to prevent guests from crashing with older perf binaries if 20b279ddb38c will be reverted. -- Gleb.