From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758114AbYDUQeT (ORCPT ); Mon, 21 Apr 2008 12:34:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754556AbYDUQeI (ORCPT ); Mon, 21 Apr 2008 12:34:08 -0400 Received: from vpn.id2.novell.com ([195.33.99.129]:22789 "EHLO vpn.id2.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754539AbYDUQeH convert rfc822-to-8bit (ORCPT ); Mon, 21 Apr 2008 12:34:07 -0400 Message-Id: <480CDE2B.76E4.0078.0@novell.com> X-Mailer: Novell GroupWise Internet Agent 7.0.3 Date: Mon, 21 Apr 2008 17:34:19 +0100 From: "Jan Beulich" To: "Ingo Molnar" , "Roland McGrath" Cc: "Thomas Gleixner" , Subject: Re: [PATCH] x86: prevent unconditional writes to DebugCtl MSR References: <20080418194334.7483627037C@magilla.localdomain> <20080421155534.GA1284@elte.hu> In-Reply-To: <20080421155534.GA1284@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> Ingo Molnar 21.04.08 17:55 >>> > >* Roland McGrath wrote: > >> If TIF_DEBUGCTLMSR is ever set on a machine without the support, that >> is a bug we should diagnose earlier. If you want some paranoia, then >> keep update_debugctlmsr but make it do: >> >> BUG_ON(boot_cpu_data.x86 < 6); >> >> instead. > >agreed. Jan, wanna send a fix for this? Hmm, without knowing the context here I'd say the way it's done in .25 is quite reasonable; a BUG_ON() here would seem quite rude to me. I thought it really should be the call sites ensuring this doesn't get called, and the silent ignoring is just to prevent bringing the system down. A WARN_ON() (or perhaps even WARN_ON_ONCE()) would be the most I'd be inclined to add there. Jan