Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934594AbaFSUlT (ORCPT ); Thu, 19 Jun 2014 16:41:19 -0400 Received: from mga03.intel.com ([143.182.124.21]:10285 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934365AbaFSUlS (ORCPT ); Thu, 19 Jun 2014 16:41:18 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,508,1400050800"; d="scan'208";a="447684311" Date: Thu, 19 Jun 2014 13:40:41 -0700 From: Andi Kleen To: Stephane Eranian Cc: LKML , Peter Zijlstra , "mingo@elte.hu" , Joe Mario , Don Zickus , Jiri Olsa , Arnaldo Carvalho de Melo Subject: Re: [PATCH 1/2] perf/x86: update Haswell PEBS event constraints Message-ID: <20140619204041.GW8178@tassilo.jf.intel.com> References: <1403193509-22393-1-git-send-email-eranian@google.com> <1403193509-22393-2-git-send-email-eranian@google.com> <20140619180028.GU8178@tassilo.jf.intel.com> <20140619201801.GV8178@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 19, 2014 at 10:31:29PM +0200, Stephane Eranian wrote: > On Thu, Jun 19, 2014 at 10:18 PM, Andi Kleen wrote: > >> I don't quite understand that. > >> You need to know which events support PEBS. You need a table > > > > We're talking about the kernel allowing things here. > > Yes the user still needs to know what supports PEBS, but > > that doesn't concern the kernel. > > > Just need to make sure you don't return bogus information. GIGO. We only need to prevent security issues. > > You can just allow it for all, it's a nop if the event doesn't > > support it. And also the fields like DataLA are simply 0 when > > not supported. > > > > Let's take a example. If I do resource_stalls:pp, the kernel > will let it go through and clear the PMI bit on the config as > is required for PEBS mode. The counter will count normally > and never fire an interrupt, even when it overflows. It would > never execute the PMI handler and thus never look at the > PEBS content. You'd never get any samples. Yes if the user specifies a bogus raw event it will not count. That's fine. The important part is just that nothing ever crashes. -Andi -- 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/