Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755586Ab3EFSyN (ORCPT ); Mon, 6 May 2013 14:54:13 -0400 Received: from 173-166-109-252-newengland.hfc.comcastbusiness.net ([173.166.109.252]:36286 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755101Ab3EFSyM (ORCPT ); Mon, 6 May 2013 14:54:12 -0400 Date: Mon, 6 May 2013 20:52:26 +0200 From: Peter Zijlstra To: Stephane Eranian Cc: Andi Kleen , Ingo Molnar , LKML , stable@vger.kernel.org, Andi Kleen Subject: Re: [PATCH 2/2] perf, x86: Don't allow unusual PEBS raw flags Message-ID: <20130506185226.GA17723@dyad.programming.kicks-ass.net> References: <1366844694-2770-1-git-send-email-andi@firstfloor.org> <1366844694-2770-2-git-send-email-andi@firstfloor.org> <20130502073720.GH7521@dyad.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1474 Lines: 33 On Mon, May 06, 2013 at 07:44:19PM +0200, Stephane Eranian wrote: > On Thu, May 2, 2013 at 9:37 AM, Peter Zijlstra wrote: > > On Wed, Apr 24, 2013 at 04:04:54PM -0700, Andi Kleen wrote: > >> From: Andi Kleen > >> > >> The PEBS documentation in the Intel SDM 18.6.1.1 states: > >> > >> """ > >> PEBS events are only valid when the following fields of IA32_PERFEVTSELx are all > >> zero: AnyThread, Edge, Invert, CMask. > >> """ > >> > >> Since we had problems with this earlier, don't allow cmask, any, edge, invert > >> as raw events, except for the ones explicitly listed as pebs_aliases. > > > > If its a simple matter of crap in crap out without affecting anything else we > > shouldn't do anything. > > > The problem here is that you are sampling an instruction which did not cause > the event you are measuring. Remember that using cmask, changes the > nature of what's being measured (from event to cycles). Yeah.. I don't see the problem though. If you're using cmask and the like you're supposed to know wth you're doing; which includes knowing your cpu and what it thinks of such an event. The only reason to disallow events is if they (badly) interact with other counters. -- 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/