From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754952Ab3GJR5i (ORCPT ); Wed, 10 Jul 2013 13:57:38 -0400 Received: from one.firstfloor.org ([193.170.194.197]:60833 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754811Ab3GJR5h (ORCPT ); Wed, 10 Jul 2013 13:57:37 -0400 Date: Wed, 10 Jul 2013 19:57:34 +0200 From: Andi Kleen To: Peter Zijlstra Cc: Andi Kleen , "Yan, Zheng" , linux-kernel@vger.kernel.org, mingo@kernel.org, eranian@google.com Subject: Re: [PATCH v2 4/7] perf, x86: Save/resotre LBR stack during context switch Message-ID: <20130710175734.GZ6123@two.firstfloor.org> References: <1372663387-11754-1-git-send-email-zheng.z.yan@intel.com> <1372663387-11754-5-git-send-email-zheng.z.yan@intel.com> <20130704095735.GL18898@dyad.programming.kicks-ass.net> <20130704134457.GS6123@two.firstfloor.org> <20130704140057.GN18898@dyad.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130704140057.GN18898@dyad.programming.kicks-ass.net> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 04, 2013 at 04:00:57PM +0200, Peter Zijlstra wrote: > On Thu, Jul 04, 2013 at 03:44:57PM +0200, Andi Kleen wrote: > > Evidently it's not read-only on Haswell at least. > > It would be ever so good if you could at least test run such patches against > semi-current chips, not only the very latest. So we tested some systems (old and new Atom, Westmere, Nehalem, *Bridge) and they all have writable TOS. Also I double checked the SDM and it actually documents these MSRs as R/W in Chapter 35 So relying on this is ok. -Andi