Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758178AbaD2RMY (ORCPT ); Tue, 29 Apr 2014 13:12:24 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.230]:4167 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756660AbaD2RMX (ORCPT ); Tue, 29 Apr 2014 13:12:23 -0400 Date: Tue, 29 Apr 2014 13:12:20 -0400 From: Steven Rostedt To: Jiri Kosina Cc: "H. Peter Anvin" , Linus Torvalds , linux-kernel@vger.kernel.org, x86@kernel.org, Salman Qazi , Ingo Molnar , Michal Hocko , Borislav Petkov , Vojtech Pavlik , Petr Tesarik , Petr Mladek Subject: Re: 64bit x86: NMI nesting still buggy? Message-ID: <20140429131220.63069221@gandalf.local.home> In-Reply-To: References: <20140429100345.3f76a5bd@gandalf.local.home> <20140429120908.61ee947f@gandalf.local.home> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.22; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.142:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 29 Apr 2014 18:51:13 +0200 (CEST) Jiri Kosina wrote: > Just to be clear here -- I don't have a box that can reproduce this; I > whole-heartedly believe that even if there are boxes with this behavior > (and I assume there are, otherwise Intel wouldn't be mentioning it in the > docs), it'd be hard to trigger on those. I see your point. But it is documented for those that control both NMIs and SMMs. As it says in the document: "If the SMI handler requires the use of NMI interrupts". That to me sounds like a system that has control over both SMIs *and* NMIs. The BIOS should not have any control over NMIs, as the OS requires that. And the OS has no control over SMIs. That paragraph sounds irrelevant to normal BIOS and OS systems as neither "owns" both SMIs and NMIs. I've fought BIOS engineers before, where they would say something like "Oh! You want to use the second PIT? I'll fix my code. Sorry". > We were hunting something completely different, and came through this > paragraph in the Intel manual, and found it rather scary. But this is all irrelevant anyway as this is all hypothetical and there's been no real world bug with this. -- Steve -- 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/