From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751358AbdBONHX (ORCPT ); Wed, 15 Feb 2017 08:07:23 -0500 Received: from mga05.intel.com ([192.55.52.43]:24642 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750711AbdBONHW (ORCPT ); Wed, 15 Feb 2017 08:07:22 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.35,166,1484035200"; d="scan'208";a="44782890" From: Alexander Shishkin To: Peter Zijlstra Cc: Arnaldo Carvalho de Melo , Ingo Molnar , linux-kernel@vger.kernel.org, vince@deater.net, eranian@google.com, Arnaldo Carvalho de Melo , Borislav Petkov , Thomas Gleixner Subject: Re: [PATCH 2/2] perf/x86/intel/pt: Fail event creation if VMX operation is on In-Reply-To: <20170215085621.GQ25813@worktop.programming.kicks-ass.net> References: <20170214132416.26400-1-alexander.shishkin@linux.intel.com> <20170214132416.26400-3-alexander.shishkin@linux.intel.com> <20170214174734.GC4458@kernel.org> <87poijkg25.fsf@ashishki-desk.ger.corp.intel.com> <20170215085621.GQ25813@worktop.programming.kicks-ass.net> User-Agent: Notmuch/0.23.5 (http://notmuchmail.org) Emacs/24.5.1 (x86_64-pc-linux-gnu) Date: Wed, 15 Feb 2017 15:05:10 +0200 Message-ID: <87d1ejk3jt.fsf@ashishki-desk.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra writes: > On Wed, Feb 15, 2017 at 10:34:58AM +0200, Alexander Shishkin wrote: > >> Well, we can't make the limitation go away. You'll still have to stop >> kvms to get any 'meaningful' PT data. > > Why would you need to stop all VMs in order to get your !VM data? Sure, > you get black holes where the VM runs, but we should be able to see > everything else. No, what I mean is that if you run kvm prior to starting perf record, which I assume is the case for acme, your entire session is a black hole. The VMXON happens pretty early on, you can open /dev/kvm, ioctl(KVM_CREATE_VM) on it and that will do a VMXON already. The problem is that PT (on BDW) doesn't trace inside VM root mode, not just between VM entry/VM exit. Regards, -- Alex