From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752894Ab0C2ONu (ORCPT ); Mon, 29 Mar 2010 10:13:50 -0400 Received: from casper.infradead.org ([85.118.1.10]:52377 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752621Ab0C2ONt (ORCPT ); Mon, 29 Mar 2010 10:13:49 -0400 Subject: Re: [RFC,PATCH 2/2] perf, x86: Utilize the LBRs for machine/oops debugging From: Peter Zijlstra To: Stephane Eranian Cc: mingo@elte.hu, Linus Torvalds , linux-kernel@vger.kernel.org In-Reply-To: References: <20100329122021.765109681@chello.nl> <20100329122138.848413757@chello.nl> Content-Type: text/plain; charset="UTF-8" Date: Mon, 29 Mar 2010 16:13:44 +0200 Message-ID: <1269872024.12097.337.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2010-03-29 at 13:47 +0100, Stephane Eranian wrote: > On Mon, Mar 29, 2010 at 1:20 PM, Peter Zijlstra wrote: > > The LBRs are relatively cheap to keep enabled and provide some history > > to OOPSen, also some CPUs are reported to keep them over soft-reset, > > which allows us to use them to debug things like tripple faults. > > > > Therefore introduce a boot option: lbr_debug=on, which always enable > > the LBRs and will print the LBRs on CPU init and die(). > > > > When this is enabled, it will prevent changing the LBR configuration to > record only selected branches. Unless you are willing to accept filtered > content in the kernel dump. Sure, but since we don't support that silly config reg anyway that's pretty much not an issue ;-)